The severe effects of CAD occur as a person ages. In general, CAD symptoms are seen in middle and old age.1 Traditionally, CAD has been regarded as a male disease, but it is increasingly obvious that in modern society it affects both genders.¹ The average age for a person having a first heart attack is 64.5 years for men and 70.3 years for women.¹ Starting at age 75 years, the prevalence of cardiovascular disease is higher among women than men.^2,3 CAD rates for postmenopausal women are two to three times higher than those for premenopausal women of the same age.¹ People of color and multiracial populations of both genders have higher CAD mortality rates than do white populations of similar socioeconomic status.¹

A positive family history is one in which a close blood relative has had a myocardial infarction (MI) or stroke before the age of 60. This family history suggests a genetic or lifestyle predisposition to the development of CAD. Individuals with a family history had a 50% greater risk of having an acute MI in the INTERHEART study.4 This was a large, international, standardized case-control study of similar cohorts in 52 countries that was designed to examine the importance of risk factors for CAD on a worldwide basis.⁴

Hyperlipidemia is a leading factor responsible for severe atherosclerosis and the development of CAD. Determining total serum cholesterol and triglyceride levels is a helpful start in the evaluation process.3,5 A lipid panel blood test can measure the following values:

Treatment of hyperlipidemia has advanced beyond the concept of lowering total cholesterol to treatment of specific lipoprotein abnormalities.^3,6–8 The target levels for specific serum lipids are listed in Table 12-1.

A diet rich in saturated fats leads to elevated cholesterol levels in the blood. The first line of treatment to lower elevated serum cholesterol is a low-fat, high-fiber diet and increased physical exercise.7,8 If these measures are not effective, lipid-lowering drugs are indicated.¹ This approach sounds simple, but less than one half of the people who qualify for lipid reduction therapy are taking their medications; only one third of treated patients reach their LDL target; and fewer than 20% of patients with CAD are at their LDL goal.¹ Although lipid-lowering drugs are very helpful for some, they are not a panacea for everyone.

Obesity is a disease of modern times. Global estimates are more than 1 billion overweight adults, and at least 300 million of these people are obese. Obesity is often associated with a sedentary lifestyle. A high risk of coronary heart disease is among the well-established adverse health effects associated with excess weight. Hypertension, hypercholesterolemia, and diabetes are among the clinical conditions that are important mediators of this association.12 In the United States in 2001, 122 million adults were overweight or obese.¹³ In 2006 144 million adults, or 66% of the U.S. adult population, were overweight or obese.¹ Obesity is defined using the body mass index (BMI).

The BMI is calculated as the weight in kilograms divided by the square of the height in meters (kg/m²); it assesses body weight relative to height. BMI is used to evaluate the threat of excess pounds as a risk factor for CAD and permits comparisons of people of different gender, age, height, and body type.¹ BMI is calculated as the weight in kilograms divided by the square of the height in meters (kg/m²). The BMI calculation in metric units is shown in Box 12-2. A normal BMI is between 18.5 and 25 kg/m². A BMI between 25 and 30 kg/m² indicates the person is overweight. A BMI greater than 30 kg/m² is the definition of obesity.¹

The distribution pattern of fat on the body is a CAD risk factor. The more weight carried in the abdominal area, producing a large waist, the greater the risk of CAD. Excess abdominal adiposity (apple body shape) indicates additional fat around the abdominal organs compared with individuals who have a smaller waist and larger hips (pear body shape). A waist size greater than 40 inches in men and 35 inches in women increases their risk for CAD. Physical exercise assists with weight reduction, lowers the risk for CAD, and decreases the risk of developing type 2 diabetes.

Regular vigorous physical activity using large muscle groups promotes physiological adaptation to aerobic exercise that can prevent the development of CAD and reduce symptoms in patients with established cardiovascular disease.14 Exercise also reduces the incidence of many other diseases, including type 2 diabetes, osteoporosis, obesity, depression, and cancers of the colon and breast.¹⁴ Many research trials have demonstrated the positive effects of physical activity on the other major cardiac risk factors.¹⁴ Exercise alters the lipid profile by decreasing LDL cholesterol and triglyceride levels and increasing HDL cholesterol levels.¹⁴ Exercise reduces insulin resistance at the cellular level, lowering the risk for developing type 2 diabetes, especially if combined with a weight-loss program.¹⁴ Epidemiological studies indicate that physical athletics as a young person do not confer protection in later years. A sedentary lifestyle has negative effects, regardless of age, gender, BMI, smoking status, presence or absence of hypertension, or abnormal lipoprotein profile. Lifelong physical activity is necessary to prevent atherosclerotic CAD and stroke.¹⁴ In 2005 the prevalence of adults not engaging in any physical activity during leisure or work time was 10.3% in the United States.¹ In affluent countries, only one third of the population exercises moderately for the recommended 30 minutes, five times per week.

Hypertension is a cardiac risk factor because the high SBP damages the arterial endothelium, leading to vascular inflammation that encourages formation of plaque. Hypertension is a complex, multifactorial disease process. Hypertension is divided into stages for the purposes of treatment, as shown in Table 12-2.

Prehypertension is an SBP of 120 to 139 mm Hg or DBP above 85 mm Hg.^1,13 In the United States, one in five adults is prehypertensive. Hypertension is diagnosed when the blood pressure is above 140/90 mm Hg. Hypertension affects another one in four adults in the United States. After the blood pressure is above 140/80 mm Hg, hypertension is described as stage 1 or stage 2 depending on the severity (see Table 12-2).

Hypertension is often described as the “silent killer,” because 30% of those affected are unaware they have seriously elevated blood pressure.¹ A higher percentage of men than women have hypertension until age 45, but from the ages of 45 to 54 years, the percentage of men and women with hypertension is similar.¹ It is essential that patients understand that sustained elevation of blood pressure leads inexorably toward atherosclerosis, heart failure, kidney failure, stroke, and heart attack.¹³ So widespread is hypertension in industrialized societies that even a normotensive person at age 55 has a 90% lifetime risk of developing hypertension. This implies that even normotensive persons should adopt interventions to maintain a normal blood pressure.¹³ The estimated direct and indirect cost of hypertension in the United States for 2010 is $76.6 billion.¹

According to recent guidelines, the goal of treatment for the hypertensive person without other risk factors is to achieve a blood pressure below 140/80 mm Hg. For the hypertensive person who already has diabetes or kidney disease, the target blood pressure is below 130/80 mm Hg. A normal blood pressure is below 120/80 mm Hg.¹³

Lifestyle interventions that can normalize blood pressure include physical exercise, a low-salt diet, limiting alcohol intake, and achieving normal body weight. Most patients are started on a diuretic, and if this is insufficient, they may be placed on an angiotensin-converting enzyme inhibitor (ACEI), angiotensin receptor blocker (ARB), beta-blocker, or calcium channel blocker. Most patients require at least two medications, each from different drug classifications, to normalize their blood pressure.¹³ Hypertensive emergencies with acute organ damage are discussed in the last section of this chapter.

The greater the number of cigarettes smoked per day, the greater the risk of developing CAD, acute MI, and stroke.14,16 In the United States, the prevalence of smoking has always been lower among women than men.¹ Cigarette smoking unfavorably alters serum lipid levels, decreases the HDL cholesterol level, and increases LDL cholesterol and triglyceride levels. In the United States, smoking remains common, with an overall prevalence of 20.6% of the adult population. Smoking increases the risk of coronary heart disease at all levels.¹ Smokers are two to four times more likely to develop CAD than nonsmokers.¹ Passive, secondhand smoke exposure also increases cardiovascular risk; 34.7% of nonsmoking adults are exposed to environmental tobacco smoke at home or at work.^15–17 Nicotine is addictive, and smoking cessation is difficult. People need tremendous support to be able to “kick the habit.” Chapter 25 provides patient education guidelines on how to stop smoking.

Individuals with diabetes mellitus (types 1 and 2) have a higher incidence of coronary heart disease compared with the general population. Data from the Framingham Heart Study indicates a doubling in the incidence of diabetes over the past 30 years and most dramatically during the 1990s.1 Elevated blood glucose level is a known risk factor for development of vascular inflammation associated with atherosclerosis. The normoglycemia range is 70 to 100 mg/dL. It is recommended that patients in critical care have blood glucose levels maintained close to the normal range¹⁸ while avoiding hypoglycemic episodes.

A fasting blood glucose concentration between 100 and 125 mg/dL represents a prediabetic state and is a risk factor for the development of diabetes and CAD (Table 12-3). A fasting blood glucose above 126 mg/dL is indicative of diabetes. Patients with diabetes have an increased risk of developing CAD and have worse clinical outcomes after acute coronary syndrome events.¹⁹ In a multinational study of patients who were seen at hospitals with symptoms of acute coronary syndrome, almost one in four had a known history of diabetes.²⁰

Chronic kidney disease is considered a risk equivalent for CAD.2,3,21 This means patients with chronic kidney disease have as much risk of experiencing a coronary event as if they already had CAD.^2,3,22 The risk of death for the patient with acute MI rises as the serum creatinine level increases.²² In one study, the in-hospital mortality rates for patients with an acute MI were 2% for patients with normal kidney function, 6% for those with mild kidney failure, 14% for those with moderate kidney failure, 21% for those with severe kidney failure, and 30% for patients with end-stage kidney disease.²² Mortality following cardiac surgery is also higher for individuals with chronic kidney disease.²³

Metabolic syndrome refers to the clustering of risk factors associated with cardiovascular disease and type 2 diabetes.1 The prevalence of metabolic syndrome in 2006 for adults in the United States was 34%.¹ Metabolic syndrome is diagnosed when three or more of the following risk factors are present:^24,25

It is perhaps obvious that individuals with the signs of metabolic syndrome are at increased risk for CAD; even so, it is surprising to what degree this holds true. In the Framingham epidemiological study, presence of the factors associated with metabolic syndrome predicted 25% of all new-onset CAD and almost 50% of new-onset diabetes.²³

Serious CAD symptoms occur approximately 5 years later in women than in men.25 The average age for the first acute MI in men is 65.8 years and in women is 70.4 years.¹ Incidence of CAD is two to three times higher among postmenopausal women than women who are premenopausal.¹ In the past, it seemed logical to prescribe hormone replacement therapy (HRT) to treat the symptoms of menopause. However, well-designed research trials discovered an increase in cardiovascular events in the first year of HRT (estrogen plus progestin), although cardiac events declined after the first year.^25,26 Subsequent studies have confirmed this result.²⁴ In 2004 the estrogen-only HRT trial was stopped by the National Institutes of Health (NIH) because of an increased risk of stroke among the women taking estrogen. For these reasons, HRT is no longer recommended for prevention of atherosclerotic cardiovascular disease.²⁷ Data from the Framingham Heart Study indicate the lifetime risk for cardiovascular disease is more than one in two for women at age 40.¹

Cardiovascular disease kills more than one-half million women annually in the United States. To emphasize the magnitude of the problem, this represents more deaths than the next seven fatal diseases for women combined.²⁸ Mortality rates for women after an acute MI are higher than for men: 38% and 25%, respectively. Risk factors more strongly associated with acute MI in women compared to men include hypertension, diabetes mellitus, alcohol intake, and physical inactivity.²⁶ Many reasons contribute to women having higher mortality from acute MI, including waiting longer to seek medical care, having smaller coronary arteries, being older when symptoms occur, and experiencing very different symptoms from those of men of the same age.²⁹ The 2007 evidence-based guidelines for cardiovascular disease prevention in women recommended a plan for a general approach to the female patient that classifies her as high risk, at risk, or at optimal risk.²⁸ In 2007 50% of women surveyed by the American Heart Association (AHA) recognized that heart disease was the leading cause of death among women.

The link between vascular inflammation and atherosclerotic disease is well established.31 Measurement of this link has been more controversial, however.³⁰ Many researchers think the development of atherosclerotic plaque occurs in response to inflammation. Noxious inflammatory agents circulate in the bloodstream and stimulate chemical mediators that directly modify the arterial wall. The initial inflammatory stimuli include increased blood glucose, elevated blood lipids, nicotine, and hypertension. However, other clinical conditions, such as connective tissue disorders and systemic infection, also produce an inflammatory state, and it is not clear what the impact of inflammation produced by these stimuli is on the vessels.³⁰ Research to identify prognostic inflammatory markers is ongoing.

The inflammatory marker most frequently cited is C-reactive protein (CRP). It is measured as high-sensitivity C-reactive protein (hs-CRP).30 The higher the hs-CRP value, the greater the risk of a coronary event, especially if all other potential causes of systemic inflammation such as infection can be ruled out. If other systemic inflammatory conditions such as bronchitis or a urinary tract infection are present, the hs-CRP test loses all predictive value.³¹ CRP and other inflammatory markers are used to estimate the probability of future acute coronary events.^30,31 During acute coronary syndrome events, there is widespread activation of neutrophils in the cardiac circulation (measured from the coronary sinus), which suggests that inflammation is not limited to one unstable plaque.³² Debate continues about whether CRP is simply a marker of vascular inflammation or also contributes to the proinflammatory state.⁹

Atherosclerosis is a chronic inflammatory disorder that is characterized by an accumulation of macrophages and T lymphocytes in the arterial intimal wall. A high LDL cholesterol concentration is one of the triggers of vascular inflammation. The inflammation injures the wall, allowing the LDL cholesterol to move into the vessel wall below the endothelial surface.9 Blood monocytes adhere to endothelial cells and migrate into the vessel wall. Within the artery wall, some monocytes differentiate into macrophages that unite with and then internalize LDL cholesterol. The foam cells that result are the marker cells of atherosclerosis.⁹

Elevated LDL cholesterol levels promote low-level endothelial inflammation that allows lipoproteins to infiltrate the intimal vessel wall. After it has infiltrated under the endothelium, LDL cholesterol tends to stay within the vessel wall rather than return to the circulation.⁹ This contrasts with the actions of HDL cholesterol, which enters the vessel wall, helps efflux cholesterol from cells, and then returns to the circulation.⁹ The actions of HDL cholesterol may help minimize the number of foam cells in the artery wall.⁹

When a mature atherosclerotic plaque develops, it is not uniform in composition. It has a lipid liquid center filled with procoagulant factors. A connective tissue fibrous cap covers the top of the fluid lipid center.30–32 The abrupt rupture of this cap allows procoagulant lipids to flood into the vessel lumen and rapidly form a coronary thrombosis, as shown in Table 12-4. As the enlarging clot blocks blood flow through the coronary artery, a “heart attack” will occur unless there is adequate collateral circulation from other coronary vessels. Symptoms and suggested cardiac interventions at appropriate stages in development of CAD are listed in Table 12-4.

TABLE 12-4

TIMELINE OF ATHEROGENESIS DEVELOPMENT DEPICTED BY LONGITUDINAL SECTION OF AN ARTERY

ATHEROGENESIS/THROMBOGENESIS	ASSOCIATED SYMPTOMS	CARDIAC INTERVENTION
A. Normal artery, normal vessel wall.	No symptoms	Primary prevention of CAD recommended: consume a low-fat diet, take regular physical exercise, avoid smoking, and achieve normal BMI
B. Lipids in bloodstream.	No symptoms
C. Extracellular lipid accumulates in the intima of the artery (atheroma).	No symptoms
D. Lipid accumulation evolves to become a fatty-fibrous (atherosclerotic) lesion. Some lesions contain a lipid interior covered by a fibrous cap.	Chest pain with exercise that is relieved by rest or NTG (stable angina) or possibly no symptoms until the lesion fills more than 75% of the vessel lumen	PCI if stable angina is present and CAD is diagnosed by cardiac catheterization
E. Rupture of the cap allows lipid in the center to be released into the bloodstream, stimulating clot formation (thrombogenesis).	Chest pain not relieved by rest or NTG (ACS – unstable angina)	Call 911 for immediate transport to a hospital, preferably one with experience treating ACS
F. Fresh clot blocks the vessel; spasm of the artery may occur near the thrombus.	Chest pain unrelieved by rest or NTG – severity, location of angina, and associated symptoms vary greatly among individuals (ACS – acute MI)	Emergency intervention to open the artery: fibrinolytic or catheter-based procedure (PCI)
G. Vessel is open, but the atherosclerotic lesion remains.	No symptoms	Secondary prevention of CAD to prevent repeat MI; beta-blockers to prevent arrhythmias; ACE-1 drugs to prevent ventricular remodeling and heart failure; elective PCI

ACE-1, angiotensin-converting enzyme 1; ACS, acute coronary syndrome; BMI, body mass index; CAD, coronary artery disease; MI, myocardial infarction; NTG, nitroglycerin; PCI, percutaneous coronary intervention.

(Modified from Antman EM, et al: ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction – executive summary, Circulation 110(5):588, 2004.)

Plaques that are likely to rupture are saturated with macrophages and other inflammatory cells. These vulnerable plaques are usually not obstructive and are situated at bends or branch points in the arterial tree.³ It is not known what factors cause the fibrous cap to rupture or erode. As deep fissures in the cap expose the procoagulant factors to the blood plasma, an unstoppable cycle is put into motion. When platelets in the bloodstream are exposed to collagen, necrotic debris, von Willebrand factor, and thromboxane, a clot is formed that can occlude the coronary artery. Highly fibrotic plaques do not rupture. The type of atherosclerotic plaque that is prone to rupture has a weak fibrous cap and a large amount of liquid cholesterol within the core (see Table 12-4).³²

A reduction in blood cholesterol decreases atherosclerotic plaque size by decreasing the amount of liquid cholesterol within the plaque core.7 Lowering cholesterol levels does not change the dimensions of the fibrous or calcified portions of the plaque. However, lower cholesterol levels reduce vascular inflammation and make vulnerable plaque less likely to rupture.

If diet is not effective in lowering blood cholesterol, lipid-lowering drugs are prescribed to lower the LDL cholesterol level below 100 mg/dL for patients at risk for CAD and to aim for an LDL level below 70 mg/dL for individuals with the highest-risk profile.⁷ Drugs, diet, and exercise are used to lower the triglyceride levels to less than 150 mg/dL, and to raise HDL cholesterol levels above 40 mg/dL for men and above 50 mg/dL for women (see Table 12-1).^3,7,8,33

Angina pectoris, or chest pain, caused by myocardial ischemia is not a separate disease, but rather a symptom of CAD. It is caused by a blockage or spasm of a coronary artery, leading to diminished myocardial blood supply. The lack of oxygen causes myocardial ischemia, which is felt as chest discomfort, pressure, or pain. Angina may occur anywhere in the chest, neck, arms, or back, but the most commonly described location is pain or pressure behind the sternum. The pain often radiates to the left arm but can also radiate down both arms and to the back, the shoulder, the jaw, or the neck (Figure 12-1). Angina symptoms are not the same for all individuals, many patients may describe pressure or discomfort rather than pain and presenting symptoms can be highly individualized, as described in Box 12-3. Patients and families must be taught that angina does not always present in the dramatic heart attack scenario seen on television and in movies, in which the person clutches the throat or chest and exhibits extreme distress.³

Complaints of chest discomfort (angina) must be evaluated quickly, because angina is an indicator of myocardial ischemia. The patient is asked to rate the intensity of the chest discomfort on a scale of 0 to 10. Pain levels must be assessed with sensitivity to differences in cultural manifestations of pain. The words “chest pain” are not to be used exclusively, because some patients describe their angina as “pressure” or “heaviness.” It is important to document the characteristics of the pain and the patient’s heart rate and rhythm, blood pressure, respirations, temperature, skin color, peripheral pulses, urine output, mentation, and overall tissue perfusion. A 12-lead ECG is used to identify the area of ischemic myocardium. The major concern is that the chest pain may represent preinfarction angina, and early identification is essential so that the patient can be immediately treated. A range of treatments are available that include fibrinolytic infusion immediately, or transfer to the cardiac catheterization laboratory for a coronary arteriogram and opening of a blocked artery. If the hospital does not have a cardiac catheterization laboratory, GP IIb/IIIa receptor blockers may be infused to prevent the evolution of the acute MI before transfer.3,5 Figure 12-2 presents additional information about transfer between hospitals in this circumstance.

In the critical care unit, control of angina is achieved by a combination of supplemental oxygen, nitrates, analgesia, and surveillance of the angina and of the effects of pharmacological therapy.

The outer region of the infarcted myocardial area is the zone of ischemia, as illustrated in Figure 12-3. It is composed of viable cells. Priority interventions are targeted to save this viable muscle. Repolarization in this zone is temporarily impaired but eventually will be restored to normal. Electrical conduction from areas of viable myocardium produces a normal QRS configuration as shown in Figure 12-4, A. Repolarization of ischemic myocardial cells manifests as T-wave inversion (see Figure 12-4, B).

The infarcted zone is surrounded by injured but still potentially viable tissue in an area known as the zone of injury (see Figure 12-3). Cells in this area do not fully repolarize because of the deficient blood supply. This is recorded on the ECG as elevation of the ST segment (see Figure 12-4, C).

The area of dead muscle (necrosis) in the myocardium is known as the zone of infarction (see Figure 12-3). On the ECG, evidence of this zone is seen by new pathological Q waves, which reflect a lack of depolarization from the cardiac surface involved in the MI (see Figure 12-4, D). As healing takes place, the cells in this area are replaced by scar tissue.

MIs are classified according to the location on the myocardial surface and the muscle layers affected. Not all infarctions cause necrosis in all layers, as shown in Figure 12-5. A transmural MI involves all three cardiac layers—the endocardium, the myocardium, and the epicardium. A transmural (full-thickness) MI usually provokes significant ECG changes (see Figure 12-4). This is also described as a Q-wave MI. Not every acute MI produces a recognizable series of Q waves on the 12-lead ECG. Some patients who had a demonstrated Q wave on a 12-lead ECG as a result of an acute MI lose the Q wave months or years later. The reasons for this are unknown, but it may represent the development of collateral circulation.

The location of infarction is determined by correlating the ECG leads with Q waves and the ST-segment T-wave abnormalities (Table 12-5). Infarction most commonly affects the left ventricle and the interventricular septum; however, the right ventricle can be infarcted, and many patients who sustain an inferior MI have some right ventricular damage. The ECG manifestations that are used to diagnose an MI and pinpoint the area of damaged ventricle include inverted T waves, ST-segment elevation, and pathological Q waves in specific lead groupings as described subsequently.

Anterior Wall Infarction

Anterior wall infarction results from occlusion of the proximal left anterior descending artery (see Table 12-5). ST-segment elevation is expected in leads V₁ through V₄ on the 12-lead ECG, as shown in Figure 12-6. If the left main coronary artery is occluded, the ECG manifestations will involve almost all of the precordial leads V₁ through V₆ and leads I and aVL (augmented voltage left) as listed in Table 12-5. The specific groups of ECG changes that help to locate the part of the heart that is infarcting are called indicative changes. A large anterior wall MI may be associated with left ventricular pump failure, cardiogenic shock, or death.³

Left Lateral Wall Infarction

Left lateral wall infarction occurs as a result of occlusion of the circumflex coronary artery. On a 12-lead ECG, new Q waves and ST-segment T-wave changes are seen in leads I, aVL, V₅, and V₆ (Figure 12-7). In reality, few patients present with only lateral wall ECG changes, and some anterior wall leads (V₃ and V₄) may show evidence of injury or infarction.

Inferior Wall Infarction

Inferior wall infarction occurs with occlusion of the right coronary artery. This infarction manifests by ECG changes in leads II, III, and aVF (Figure 12-8). Conduction disturbances are expected with an inferior wall MI and are related to the anatomy of the coronary arterial supply. Because the right coronary artery perfuses the sinoatrial (SA) node in slightly more than half of the population and supplies the proximal bundle of His and atrioventricular (AV) node in more than 90% of individuals, heart block and other conduction disturbances should be anticipated. Inferior wall MI carries a mortality rate of about 6%. If the right ventricle is involved, the mortality rate increases to 25% to 30%.³

The 12-lead ECG is a highly useful diagnostic tool. For many years, it was considered the gold standard when diagnosing an acute MI. However, the ST segment is not elevated in every acute MI. One reason for the lack of ST-segment elevation may be that the infarction and subsequent necrosis are not full-thickness lesions. Because some of the muscle in the area can still be depolarized, ST-segment elevation may not occur. This type of MI is also less likely to develop Q waves on a subsequent 12-lead ECG after the acute phase has passed. This situation is diagnostically known as an NSTEMI.5 This condition has previously been described by several names, including nontransmural MI, non-Q-wave MI, and subendocardial MI. Because patients who sustain an NSTEMI do have CAD, it is important that they be treated aggressively to minimize the size of the infarcted area. Without the visual clue of the ST-segment elevation on the 12-lead ECG, the patients cannot receive immediate intravenous fibrinolytic agents, but they can be appropriately managed in an interventional catheterization laboratory and receive GP IIb/IIIa inhibitor therapy, as illustrated in the timeline in Figure 12-2. The 12-lead ECG plays a vital role in identifying the treatment plan for an ACS. ST-segment elevation is helpful when present, but it would be a mistake to believe the patient is not in danger of MI if the ST segment is not elevated. In this case, the definitive diagnosis may be made in the cardiac catheterization laboratory or by elevation of specific cardiac biomarkers.

In the presence of damaged or necrotic myocardial muscle cells, cardiac biomarkers are released. These biomarkers are also called cardiac enzymes. To confirm the diagnosis of acute MI, the serum biomarkers creatine kinase-muscle/brain (CK-MB) and troponin I or troponin T are measured. If the coronary artery is opened by fibrinolytic therapy or a percutaneous catheter intervention (PCI), the biomarkers exhibit a more rapid rise and dramatic fall (Figure 12-9). Information on biomarkers is also shown in Table 11-14 in Chapter 11.

Many patients experience complications occurring early or late in the postinfarction course. These complications may result from electrical dysfunction or from a cardiac contractility problem. The presence of a new murmur in a patient with an acute MI warrants special attention because it may indicate rupture of the papillary muscle. Electrical dysfunctions include bradycardia, bundle branch blocks, and various degrees of heart block. Pumping complications cause heart failure, pulmonary edema, and cardiogenic shock.3 The murmur can be indicative of severe damage and impending complications such as heart failure and pulmonary edema.

Ventricular Aneurysm After Myocardial Infarction

A ventricular aneurysm (Figure 12-10) is a noncontractile, thinned left ventricular wall that results from an acute transmural infarction. It most often occurs in the setting of an acute left anterior descending artery occlusion with a wide area of infarcted myocardium.² The most effective prevention is early reperfusion of the myocardium, accomplished by opening the thrombosed coronary artery. In one study, the rate of ventricular aneurysm was reduced from 19% in untreated patients to 7% when the coronary artery was opened by fibrinolysis.² The most common complications of a ventricular aneurysm are acute heart failure, systemic emboli, angina, and VT. Treatment is directed toward management of these complications and surgical repair by left ventricular aneurysmectomy. The affected area may be described as hypokinetic (contracts poorly), akinetic (noncontractile scar tissue), or dyskinetic (scar tissue that moves in the opposite direction of the normal contractile myocardium). The prognosis depends on the size of the aneurysm, the level of overall left ventricular dysfunction, and the severity of coexisting CAD.

Ventricular Septal Rupture After Myocardial Infarction

Postinfarction rupture of the ventricular septal wall is a rare but potentially lethal complication of an acute anterior wall MI (Figure 12-11). Ventricular septal rupture, also known as an acquired ventricular septal defect (VSD), is an abnormal communication between the right and left ventricle. This complication occurs in less than 1% of all MIs, and the incidence has declined because most STEMI patients have the blocked coronary artery opened.² Nevertheless, rupture of the ventricular septum carries an extremely high mortality rate.⁴⁰ Mortality rates between 35% and 73% are typical.^41,42 Most patients with septal rupture also have signs and symptoms of cardiogenic shock. Ventricular septal rupture manifests as severe chest pain, syncope, hypotension, and sudden hemodynamic deterioration caused by shunting of blood from the high-pressure left ventricle into the low-pressure right ventricle through the new septal opening. A holosystolic murmur (often accompanied by a thrill) can be auscultated and is best heard along the left sternal border. A diagnosis of postinfarction ventricular septal rupture can be made at the bedside with use of oxygen saturation assessment by means of a pulmonary artery catheter or by transesophageal echocardiography (TEE). Rupture of the septum is a medical and surgical emergency. The patient’s condition is stabilized with vasodilators and an intraaortic balloon pump (IABP) to decrease afterload.⁴² The goal of afterload reduction in this patient population is to decrease the amount of blood being shunted to the right side of the heart and consequently to increase the flow of blood to the systemic circulation. If the septal rupture is very small, and the patient’s condition is sufficiently stable to wait for scar tissue to form before surgical repair, survival improves. Unfortunately, when the septal opening is large, the massive left-to-right shunt across the septum makes the chances of survival dismal with or without surgery.^41,42

Papillary Muscle Rupture After Myocardial Infarction

Papillary muscle rupture can occur when the infarct involves the area around one of the papillary muscles that support the mitral valve. Infarction of the papillary muscles results in ineffective mitral valve closure, and blood is forced back into the low-pressure left atrium during ventricular systole. The rupture may be partial or complete. Complete rupture is catastrophic and precipitates severe acute mitral regurgitation, cardiogenic shock, and high risk of death.

Partial rupture of the valve structures (Figure 12-12) also results in mitral regurgitation, but the condition can be stabilized with aggressive medical management using the IABP and vasodilators. Urgent surgical intervention is required to replace the mitral valve.⁴³ As with other structural complications during acute MI, the incidence is decreased in patients who have their myocardium reperfused early.² Of the patients with acute MI who are admitted to the critical care unit in cardiogenic shock, 10% have papillary muscle rupture with acute mitral regurgitation. The mortality rate is 71% with medical treatment and 40% with surgical intervention to replace or repair the mitral valve.²

The essential immediate interventions are fibrinolytic therapy or PCI to open the occluded artery for the patient with an acute STEMI.2 All clinical guidelines emphasize the need for patients with symptoms of ACS to be rapidly triaged and treated.²

In the acute phase after STEMI, heparin is administered in combination with fibrinolytic therapy to recanalize (open) the coronary artery.2 For patients who will receive fibrinolytic therapy, an initial heparin bolus of 60 units/kg (maximum 4000 units) is given intravenously, followed by a continuous heparin drip at 12 units/kg/hr (maximum 1000 units/hr) to maintain an activated partial thromboplastin time (aPTT) between 50 and 70 seconds (1.5 to 2.0 times control). Alternatively, LMWH may be used at doses that provide full anticoagulation.²

It is also prudent to administer intravenous UFH or subcutaneous LMWH if the person is at risk for thrombus development.² For patients with known heparin-induced thrombocytopenia (HIT),⁵⁰ a third class of antithrombotic drugs is available as an alternative to LMWH or UFH. These are direct antithrombotic agents (e.g., hirudin, bivalirudin, argatroban, fondaparinux). Use of newer antithrombotic drugs remains low in clinical practice, however.⁵² Patients at risk for thrombotic emboli include those with an anterior wall infarction, atrial fibrillation, previous embolus, cardiomyopathy, or cardiogenic shock.

When the risk of systemic embolic complications remains high, especially in atrial fibrillation, the patient should be anticoagulated with warfarin (Coumadin).²

The antidysrhythmic with the best safety record after STEMI is amiodarone. The reduction in death related to decreased dysrhythmias after MI is 13%.2 Beta-blockers are another class of antidysrhythmics that are recommended for all patients after STEMI. Beta-blockers prevent ventricular dysrhythmias, lower blood pressure, and prevent reinfarction, especially in patients with left ventricular dysfunction.²

Achievement of normal blood glucose levels during the acute phase and after MI improves survival.2

Many patients are at risk of developing heart failure after STEMI. Vasodilating drugs known as ACEIs or ARBs can stop or limit the ventricular remodeling that leads to heart failure. An ACEI is used, or if it is not tolerated, an ARB is indicated for all patients after STEMI.2 Information about the clinical effects of heart failure is provided later in this chapter.

In the acute period, if severe heart muscle damage has occurred, myocardial oxygen supply is increased by the administration of supplemental oxygen to prevent tissue hypoxia. Drugs play an increasingly important role in balancing tissue oxygen supply and demand, and it is the critical care nurse who administers and monitors the effectiveness of these agents. For the patient with a low cardiac output, positive inotropic drugs such as dobutamine, dopamine, and milrinone are prescribed. These inotropic agents are used to increase cardiac contractility in the healthy areas of the heart (increasing oxygen supply), while avoiding damage to the recently infarcted areas. Myocardial oxygen supply can be further enhanced by the use of coronary artery vasodilators. Nitroglycerin is recommended for the first 48 hours to increase vasodilation and prevent myocardial ischemia.2 Research evidence supports the administration of early beta-blockade therapy to decrease myocardial workload and to prevent dysrhythmias. Administration of beta-blockers reduces mortality by 14% in the first 7 days after an MI and by 23% in the long-term.² However, if the patient is in cardiogenic shock, beta-blockers are withheld until the cardiac output has improved.² Other interventions to decrease cardiac work and myocardial oxygen consumption include bed rest with bedside commode privileges when the patient is clinically stable.

A thorough grasp of the range of potential complications that can occur after STEMI is essential. Cardiac monitoring for early detection of ventricular dysrhythmias is ongoing. Assessment for signs of continued ischemic pain is important, because angina is a warning sign of myocardium at risk. In response to angina, a 12-lead ECG is obtained to determine if there is an extension of the infarct, nitroglycerin is administered, and the physician is notified immediately so that interventions may be initiated to limit the size of the MI. Heart failure is a serious complication after STEMI. When the patient’s blood pressure is stable, treatment with ACEI is initiated. These vasodilators are used to prevent the left ventricular remodeling and dilation that occurs in many patients after an acute MI. Hypotension is a potential complication of ACEI, especially with the first dose. It is an important nursing responsibility to monitor blood pressure and patient symptoms after taking this medication. Surveillance to detect obvious and subtle signs of bleeding is also a priority because so many acute MI patients receive antiplatelet, anticoagulant, and fibrinolytic medications.2

In the first 24 hours, stable patients with acute MI may be given only a light diet, because their appetite is often poor. It is no longer considered necessary to restrict iced fluids or caffeine. While the patient is in bed, an upright position is preferred to foster better lung expansion. Deep breathing decreases the risk of atelectasis. An upright position also decreases venous return, lowers preload, and decreases cardiac work. The patient is taught to avoid increasing intraabdominal pressure (Valsalva maneuver). Stool softeners are given to the patient to lessen the risk of constipation from analgesics and bed rest and to decrease the risk of straining. The nurse controls the critical care unit environment by decreasing noise, diminishing sensory overload, and allowing adequate rest periods. (Evidence-Based Collaborative Practice box on Acute Coronary Syndrome and Acute Myocardial Infarction (Non-STEMI and STEMI).)

After the acute phase has passed, education for the patient and family focuses on risk-factor reduction, manifestations of angina, when to call a physician or emergency services, medications, and resumption of physical and sexual activity. If possible, a referral is made to a cardiac rehabilitation program so that this education can be reinforced outside the acute care hospital environment.51

Depending on the length of time the patient was unconscious following the cardiac arrest, cognitive defects can occur, caused by lack of cerebral blood flow and resultant hypoxia to the brain. For comatose patients at high risk for hypoxic brain injury after cardiac arrest, therapeutic hypothermia to about 33° centigrade is initiated for several hours to preserve brain function.58,59 Only one tenth to one third of people who are resuscitated after cardiac arrest are discharged from the hospital and able to lead an independent life.⁵⁹ Post-arrest hypothermia treatment increases the likelihood that survivors of cardiac arrest will leave the hospital without major brain damage.⁵⁹

Survivors receive antidysrhythmic agents and may also have an implantable cardioverter defibrillator (ICD) unit inserted.^59–62 Prevention focuses on identification and treatment of high-risk cardiac patients (see “Implantable Cardioverter Defibrillator” and “Antidysrhythmic Drugs” in Chapter 13).

Failure of the left ventricle is defined as a disturbance of the contractile function of the left ventricle, resulting in a low cardiac output state. This leads to vasoconstriction of the arterial bed that raises systemic vascular resistance (SVR), a condition also described as “high afterload,” and creates congestion and edema in the pulmonary circulation and alveoli. Clinical manifestations include decreased peripheral perfusion with weak or diminished pulses; cool, pale extremities; and in later stages, peripheral cyanosis (Table 12-7). Over time, with progression of the disease state the fluid accumulation behind the dysfunctional left ventricle elevates pulmonary pressures, contributes to pulmonary congestion and edema, and produces dysfunction of the right ventricle, resulting in failure of the right side of the heart.

Failure of the right side of the heart is defined as ineffective right ventricular contractile function. Pure failure of the right ventricle may result from an acute condition such as a pulmonary embolus or a right ventricular infarction, but it is most commonly caused by failure of the left side of the heart. The common manifestations of right ventricular failure are jugular venous distention, elevated central venous pressure (CVP), weakness, peripheral or sacral edema, hepatomegaly (enlarged liver), jaundice, and liver tenderness. Gastrointestinal symptoms include poor appetite, anorexia, nausea, and an uncomfortable feeling of fullness (see Table 12-7).

Systolic dysfunction describes an abnormality of the heart muscle that markedly decreases contractility during systole (ejection) and lessens the quantity of blood that can be pumped out of the heart. Patients with a diagnosis of systolic heart failure have signs and symptoms of heart failure combined with a below-normal ejection fraction. Left ventricular systolic dysfunction is the classic picture that most clinicians consider when thinking about heart failure. In addition to the signs and symptoms of left heart failure (described earlier), the patient has a low ejection fraction. There is some debate about how low the ejection fraction has to be to qualify as systolic heart failure, but the value is usually below 50%;64 some clinicians cite numbers below 45% or 40%.^65,66 Symptoms of heart failure with systolic dysfunction include dyspnea, exercise intolerance, and fluid volume overload.

Diastolic dysfunction describes an abnormality of the heart muscle that makes it unable to relax, stretch, or fill during diastole. The ejection fraction can be normal or abnormal (low), and the patient may be symptomatic or symptom-free.64,67,68 Half of patients with heart failure have diastolic muscle dysfunction.⁶⁹ The principal causes are similar to systolic heart failure: CAD, myocardial ischemia, uncontrolled hypertension, and left ventricular hypertrophy.⁶⁷ Some conditions that are known to markedly alter diastolic function include hypertrophic cardiomyopathy, restrictive cardiomyopathy, and infiltrative diseases such as amyloidosis and neoplastic infiltrate.

It is impossible to determine whether a patient has systolic or diastolic heart failure from clinical assessment alone.64 Both types of heart failure produce similar signs and symptoms, and in most patients systolic and diastolic dysfunction coexist.⁶³ The level of symptoms and quality of life varies between individuals, even when the ejection fraction and presumed cardiac dysfunction are the same.⁷⁰ This may occur because most symptoms occur as a result of neurohormonal compensatory mechanisms (described later) rather than changes in cardiac output.

The definitive diagnosis of the type of heart failure is often made using Doppler echocardiography. An echocardiogram performed at rest and during exercise (stress echo) permits visualization of heart wall movement during systole and diastole. Calculation of the ejection fraction can be determined using Doppler echocardiography or during a cardiac catheterization. These diagnostic tests also show when combined systolic and diastolic dysfunction coexist.64

The annual mortality rate for diastolic heart failure is 5% to 8%, markedly less than the 10% to 15% annual mortality for patients with systolic heart failure. To put this in perspective, age-matched controls without any heart failure have an annual mortality rate of just 1%.^64,67

It is not possible to distinguish whether a patient has systolic or diastolic heart failure simply by looking at the medications he or she is prescribed. The same drugs are used to treat the two types of heart failure, although the underlying rationales may be different.⁶⁵ For example, beta-blockers are used in diastolic heart failure to slow the heart rate, to prolong diastole to give more time for ventricular filling, and to modify the ventricular response to exercise, especially for patients who have a preserved ejection fraction.⁶⁵ When beta-blockers are prescribed for treatment of systolic heart failure, the intent is to preserve long-term inotropic (contractile) function and prevent ventricular remodeling.⁶⁵ Diuretics are used to treat both types of heart failure, although a smaller dosage is generally needed in diastolic heart failure.⁶⁵ ACEIs and ARBs are also used to treat both types of heart failure. The medications used to treat heart failure are further discussed in Chapter 13 (see Table 13-19).

Acute or chronic heart failure is determined by the rapidity with which the syndrome develops, the presence and activation of compensatory mechanisms, and the presence or absence of fluid accumulation in the interstitial space (see Figure 12-13). In clinical practice guidelines, the terms acute and chronic have replaced the older name of congestive heart failure (CHF), because not all heart failure involves pulmonary congestion.⁶³ However, the descriptor CHF remains in common parlance in clinical practice.

Acute heart failure has a sudden onset, with no compensatory mechanisms. The patient may experience acute pulmonary edema, low cardiac output, or even cardiogenic shock. Patients with chronic heart failure are hypervolemic, have sodium and water retention, and have structural heart chamber changes such as dilation or hypertrophy.⁶³

Chronic heart failure is ongoing, with symptoms that may be made tolerable by medication, diet, and a reduced activity level. The deterioration into acute heart failure can be precipitated by the onset of dysrhythmias, acute ischemia, sudden illness, or cessation of medications. This may necessitate admission to a critical care unit. Hypertension is the primary precursor of heart failure in women, whereas CAD, specifically acute MI, is the primary cause of heart failure in men.⁶³

BNP and NT-proBNP: Natriuretic peptides are released from the cardiac ventricles in response to increased wall tension. Heart failure increases left ventricular wall tension because of the excess preload in the ventricles causing increased wall stretch. The peptides are measured as brain natriuretic peptide (BNP) and N-terminal proB type natriuretic peptide (NT-proBNP).63

When the BNP blood level is greater than 100 pg/mL, the dyspnea is more likely to be related to cardiac rather than pulmonary failure.^76–78 A BNP result greater than 400 is considered indicative of heart failure. The more severe the heart failure, the higher the BNP test result.⁷⁹ If the patient has concomitant kidney failure, the BNP clinical diagnostic cut-point to diagnose heart failure rises to greater than 200 pg/mL.⁸⁰ See Chapter 11, Figure 11-48 for more information on using BNP to diagnose heart failure.

Breathlessness in heart failure is described by the following terms:

The alveolus is the primary site of gas exchange (Figure 12-15, A). Pulmonary edema, or protein-laden fluid in the alveoli, inhibits gas exchange by impairing the diffusion pathway between the alveolus and the capillary. It is caused by increased left atrial and ventricular pressures and results in an excessive accumulation of serous or serosanguineous fluid in the interstitial spaces and alveoli of the lungs. The formation of pulmonary edema has two stages. The first stage is not as severe and is characterized by interstitial edema, engorgement of the perivascular and peribronchial spaces, and increased lymphatic flow (see Figure 12-15, B). The later stage is characterized by alveolar edema resulting from fluid moving into the alveoli from the interstitium (see Figure 12-15, C). Eventually, blood plasma moves into the alveoli faster than the lymphatic system can clear it, interfering with diffusion of oxygen, depressing the arterial partial pressure of oxygen (PaO₂), and leading to tissue hypoxia (see Figure 12-15, D).

Heart failure patients in pulmonary edema are extremely breathless and anxious and have a sensation of suffocation. They expectorate pink, frothy liquid and feel as if they are drowning. They may sit bolt upright, gasp for breath, or thrash about. The respiratory rate is elevated, and accessory muscles of ventilation are used, with nasal flaring and bulging neck muscles. Respirations are characterized by loud inspiratory and expiratory gurgling sounds. Diaphoresis is profuse, and the skin is cold, ashen, and sometimes cyanotic, reflecting low cardiac output, increased sympathetic stimulation, peripheral vasoconstriction, and desaturation of arterial blood.

In the acute phase of advanced heart failure, the patient may have a pulmonary artery catheter in place so that left ventricular function can be followed closely. Control of symptoms involves management of fluid overload and improvement of cardiac output by decreasing SVR and increasing contractility. Diuretics are administered to decrease preload and to eliminate excess fluid from the body.73 If pulmonary edema develops, additional diuretics are used. Morphine is given to facilitate peripheral dilation and decrease anxiety. Afterload is decreased by vasodilators, such as sodium nitroprusside (Nipride) and nitroglycerin. Nitrates are used to decrease preload and vasodilate the coronary arteries if CAD is an underlying cause of the acute heart failure. For some patients, an intraaortic balloon pump (IABP) is temporarily required.⁸⁶ Contractility is initially increased by continuous infusion of positive inotropic drugs (dopamine) or by combination inodilators such as dobutamine or milrinone. Nesiritide (Natrecor) or intravenous BNP is indicated for the relief of patients with acutely decompensated heart failure who have dyspnea at rest. Nesiritide lowers pulmonary artery pressures and wedge pressure, which decreases symptoms of dyspnea.^87,88

After the acute heart failure is controlled, the patient is weaned off intravenous medications, which are gradually replaced by oral agents. Before the transition out of the critical care unit, the heart failure patient will receive ACEIs to inhibit left ventricular chamber remodeling and to slow left ventricular dilation.^63,71,74 If the patient does not tolerate ACEIs, ARBs may be substituted.⁷⁴ Low dosage beta-blockers such as carvedilol may also be prescribed, although strict surveillance is required to anticipate and avoid untoward negative inotropic effects.^83,89 Digoxin may be added to the regimen, especially if the person has concomitant atrial fibrillation.⁸⁵

Nonpharmacological interventions that are increasingly used include cardiac resynchronization therapy (CRT).⁹⁰ CRT is biventricular pacing where the right and left ventricles each have a pacing lead in contact with the myocardium. The right ventricular lead is inside the right ventricle, and the left ventricular lead is positioned into a left wall tributary of the coronary sinus vein.^90,91 In newer permanent pacemaker models, the right and left ventricular leads are paced to synchronize the ventricles and improve heart failure symptoms.

In 2004 a consensus statement on palliative and supportive care in advanced heart failure was published.92 Because heart failure is a progressive disease, some patients will not recover.⁶³ At some point, many NYHA class-IV heart failure patients will become candidates for palliative care.⁹² The primary aim of palliative care is symptom management. Symptom-management strategies are deployed to emphasize relief from suffering. Fundamental to all symptom-management strategies for heart failure is the optimization of medications according to current guidelines. The most common symptoms of advanced heart failure are dyspnea, pain, and fatigue.⁹²

The patient’s ECG is evaluated for any dysrhythmias that may be present or may develop as a result of drug toxicity or electrolyte imbalance. Patients with heart failure are prone to digoxin toxicity because of decreased renal perfusion; they are also prone to electrolyte imbalances. Breath sounds are auscultated frequently to determine the adequacy of respiratory effort and to assess for onset or worsening of pulmonary congestion. Oxygen through a nasal cannula is administered to relieve dyspnea. Diuretics or vasodilators are used to decrease excessive preload and afterload.75,88 If the patient is not hypotensive, morphine may be administered to decrease hyperventilation and anxiety. If the patient’s ventilatory status worsens, the nurse must be prepared for endotracheal intubation and mechanical ventilation. Obtaining daily weights is important until the weight stabilizes at a “dry” weight. Generally, the daily weight is used in fluid management and a weekly weight is optimally used for tracking body weight (e.g., muscle, fat).

Patients experiencing acute heart failure require aggressive pharmacological therapy.82,88,93,94 The nurse must know the action, side effects, therapeutic levels, and toxic effects of the diuretics and vasodilators used to decrease preload, the positive inotropic agents used to increase ventricular contractility, the vasodilators used to decrease afterload, and any antidysrhythmics used to control heart rate and prevent dysrhythmias. The patient’s hemodynamic response to these agents is closely monitored. Fluid intake and output balances are tabulated daily or even hourly in the critical care unit.

The nurse assesses the patient’s and family’s understanding of the pathophysiology and individual risk-factor profile for heart failure.95 Primary topics of education include the importance of a low-salt diet, daily weight, fluid restrictions, and written information about the multiple medications used to control the symptoms of heart failure.^63,96 Many patients with a diagnosis of heart failure also require education about lifestyle changes such as smoking cessation, weight loss, energy conservation, and how to incorporate exercise and sodium restriction into their daily lives.^74,97,98 Achieving the optimal outcomes for the patient with heart failure requires contributions from a team of educated health care clinicians.^63,74,97,98 Collaborative multidisciplinary goals, developed from clinical practice guidelines for management of the patient with symptoms of heart failure, are listed in the Evidence-Based Collaborative Practice box on Heart Failure.

Hypertrophic cardiomyopathy (HCM) is a genetically inherited disease that affects the myocardial sarcomere.99–102 As HCM progresses, the left ventricle becomes stiff, noncompliant, and hypertrophied, sometimes in an asymmetric fashion.⁹⁹ HCM occurs in two forms. A well-known, but less frequent, manifestation is a stiff, noncompliant myocardial muscle with left ventricular hypertrophy and bizarre cellular hypertrophy of the upper ventricular septum. This left ventricular septal hypertrophy obstructs outflow through the aortic valve, especially during exercise (see Figure 12-16, A). It also pulls the papillary muscle out of alignment, causing mitral regurgitation. This form of HCM was previously known as idiopathic hypertrophic subaortic stenosis (IHSS); however, because IHSS does not describe all patients with hypertrophied hearts, the more general term of HCM is now used.⁹⁹ Other patients with HCM have generalized left ventricular hypertrophy, but the septum is not more enlarged than the rest of the myocardium.⁹⁹ HCM causes significant diastolic dysfunction because the muscle-bound, stiff, noncompliant heart muscle cannot fill adequately during diastole.

Two advances in diagnostic medicine have propelled understanding of the differences between these two forms of HCM. Two-dimensional transthoracic echocardiography (TTE) is often useful as the first diagnostic test to identify HCM.⁹⁹ TTE enables visualization of the septal anatomy, septal movement, and ventricular wall thickness and motion. The second advance is diagnostic genetics. Genetic testing for HCM usually is performed at a center with expertise in this area.⁹⁹ HCM is inherited as an autosomal dominant trait, and the clinical expression is caused by mutations in any of one of 10 genes. Each different gene encodes different protein components of the myocardial sarcomere.⁹⁹ Genetic analysis is an expanding research area that will help clarify diagnosis and treatment options for this cardiomyopathy.¹⁰¹

Symptoms are similar to those seen with heart failure plus the symptoms of myocardial ischemia, supraventricular tachycardia (SVT), VT syncope, and stroke. Symptoms usually are more intense with physical exercise, especially in the obstructive form of HCM, in which the aortic outflow tract is obstructed by the enlarged left ventricular septum. Because there is a known association between HCM and SCD, limitation of physical activity may be recommended. Causes of SCD are thought to stem from ventricular dysrhythmias and atrial fibrillation.⁹⁹ Episodes of paroxysmal atrial fibrillation occur in 20% to 25% of HCM patients.⁹⁹ The atrial dysrhythmias are related to increased age and atrial enlargement.⁹⁹ Pharmacological management includes beta-blockers to decrease left ventricular workload, medications to control and prevent atrial and ventricular dysrhythmias, anticoagulation if atrial fibrillation or left ventricular thrombi are present, and drugs to manage heart failure. Interventional procedures include insertion of an ICD to decrease the risk of SCD, and percutaneous alcohol ablation of the intraventricular septum to decrease the size of the septal wall.^99,102 Surgical procedures such as septal myectomy and mitral valve replacement are options used less frequently than in the past.⁹⁹

Dilated cardiomyopathy is characterized by gross dilation of both ventricles without muscle hypertrophy (see Figure 12-16, C). There are several distinct causes of dilated cardiomyopathy. It is estimated that 30% of patients with dilated cardiomyopathy may have a genetic cause.⁶³

Restrictive cardiomyopathy is the least commonly encountered cardiomyopathy in industrialized societies (see Figure 12-16, B). As with the other cardiomyopathies, this form can be idiopathic or can have a known cause.^108,109 Restrictive cardiomyopathy results in ventricular wall rigidity as a consequence of myocardial fibrosis. The overall effect is the diastolic inhibition of ventricular filling. Diastolic heart failure, low cardiac output, dyspnea, orthopnea, and liver engorgement are the most common clinical manifestations of restrictive cardiomyopathy. Medical management includes beta-blockers to slow the heart rate and allow more time for ventricular filling, diuretics to remove excess fluid, and a low-sodium diet.

Mitral valve stenosis describes a progressive narrowing of the mitral valve orifice. Primary cause is rheumatic endocarditis with rare occurrences related to congenital malformations. Mitral stenosis occurs in twice as many women as men.111 Symptoms occur when the normal valve size is reduced to 2 cm² or less. Symptoms occur at rest when the valve area is reduced below 1 cm².¹¹¹ Narrowing is caused by aging valve tissue or by acute rheumatic valvulitis (Table 12-8, A). The diffuse valve leaflets fibrose and fuse, reducing mobility and thickening the chordae tendineae. As a result, the mitral valve can no longer open or close passively in response to left atrial and ventricular pressure changes. Blood flow across the valve is impeded. Mitral stenosis increases the risk of developing atrial fibrillation because of the high pressures in the left atrium that will stimulate left atrial remodeling and enlargement. Development of atrial fibrillation will significantly increase symptoms and may increase the need for surgical replacement of the valve.

TABLE 12-8

VALVULAR DYSFUNCTION

	PATHOPHYSIOLOGY	CLINICAL MANIFESTATIONS	PHYSICAL SIGNS
	Mitral Valve Stenosis
	Left atrium must generate more pressure to propel blood beyond the lesion Rise in left atrial pressure and volume reflected retrograde into pulmonary vessels Right ventricular hypertrophy Right ventricular failure	Dyspnea on exertion Fatigue and weakness Pronounced respiratory symptoms (e.g., orthopnea, paroxysmal nocturnal dyspnea) Mild hemoptysis with bronchial capillary rupture Susceptibility to pulmonary infections	Chest radiograph: pulmonary congestion, redistribution of blood flow to upper lobes ECG: atrial fibrillation and other atrial dysrhythmias Auscultation: diastolic murmur, accentuated S1, opening snap Catheterization: elevated pressure gradient across valve; increased left atrial pressure, pulmonary artery wedge pressure, and pulmonary artery pressure; low cardiac output
	Mitral Valve Regurgitation
	LV dilation and hypertrophy Left atrial dilation and hypertrophy	Weakness and fatigue Exertional dyspnea Palpitations Severe symptoms precipitated by LV failure, with consequent low output and pulmonary congestion	Chest radiograph: left atrial and LV enlargement, variable pulmonary congestion ECG: P mitrale, LV hypertrophy, atrial fibrillation Auscultation: murmur throughout systole Catheterization: opacification of left atrium during LV injection, v waves, increased left atrial and LV pressures Variable elevations of pulmonary pressures
	Aortic Valve Stenosis
	LV hypertrophy Progressive failure of ventricular emptying Pulmonary congestion Failure of right side of heart, with systemic venous congestion Sudden cardiac death	Exertional dyspnea Exercise intolerance Syncope Angina Heart failure (LV failure)	Chest radiograph: post-stenotic aortic dilation, calcification ECG: LV hypertrophy Auscultation: systolic ejection murmur Catheterization: significant pressure gradient, increased LV end-diastolic pressure
	Aortic Valve Regurgitation
	Increased volume load imposed on LV LV dilation and hypertrophy	Fatigue Dyspnea and exertion Palpitations	Chest radiograph: boot-shaped elongation of cardiac apex ECG: LV hypertrophy Auscultation: diastolic murmur Catheterization: opacification of LV during aortic injection Peripheral signs: hyperdynamic myocardial action and low peripheral resistance
	Tricuspid Valve Stenosis
	Right atrium must generate higher pressure to eject blood beyond the lesion Right atrial dilation Systemic venous engorgement Increased venous pressure	Venous distention Peripheral edema Ascites Hepatic engorgement Anorexia	Chest radiograph: right atrial enlargement ECG: right atrial enlargement (P pulmonale) Auscultation: diastolic murmur Catheterization: elevated right atrial pressure with large a waves; pressure gradient across the tricuspid valve
	Tricuspid Valve Regurgitation
	Right ventricular hypertrophy and dilation	Decreased cardiac output Neck vein distention Hepatic engorgement Ascites Edema Pleural effusions	Chest radiograph: right atrial and ventricular enlargement ECG: right ventricular hypertrophy and right atrial enlargement, atrial fibrillation Auscultation: murmur throughout systole Catheterization: elevated right atrial pressure and v waves

ECG, electrocardiogram; LV, left ventricular; P mitrale, m-shaped P waves that occur in left atrial hypertrophy and are often caused by mitral stenosis; P pulmonale, tall, peaked P waves that occur in right atrial hypertrophy and are often caused by chronic pulmonary disease.

Mitral valve regurgitation may result from rheumatic disease, aging of the valve, endocarditis, collagen vascular disease, or papillary muscle dysfunction111 (see Table 12-8, B). In mitral regurgitation, the valve annulus, leaflets, chordae tendineae, and papillary muscles may all be dysfunctional, or the dysfunction may be isolated to just one component of the valve. Mitral valve regurgitation results in retrograde flow of blood into the left atrium with each ventricular contraction. It is always described as chronic or acute because of the very different impact on the left-sided chambers.

With chronic mitral valve regurgitation, the left atrium has dilated to accommodate the additional regurgitant volume, whereas the left ventricle has hypertrophied (increased muscle) to maintain an adequate stroke volume and cardiac output. In contrast, acute mitral valve regurgitation is precipitated by chordae tendineae or papillary muscle rupture resulting from an acute MI or infectious endocarditis.¹¹¹ This is a medical emergency. The left atrium cannot accommodate the sudden increase in volume and pressure, and use of an IABP and inotropic drug support is often required to increase forward output and reduce pulmonary congestion. After the patient’s condition has stabilized, surgical replacement or repair of the incompetent valve is performed.¹¹¹

Aortic valve stenosis describes a narrowing of the aortic valve area. It can result from aging, rheumatic valvulitis, or deterioration of a congenital bicuspid valve111 (see Table 12-8, C). The pathological hallmarks are inflammation, fibrous valvular thickening, and tissue calcification. When the aortic valvular opening is reduced to less than 1.5 cm², the condition is classified as mild. Cardiac catheterization or Doppler echocardiography can identify a gradient of less than 25 mm Hg across the valve.¹¹² The gradient represents the difference in systolic pressure between the left ventricle and the aorta. A significant pressure difference is a diagnostic hallmark of valvular stenosis. If the valve orifice has narrowed to 1 cm² or less, the gradient will be greater than 40 mm Hg, and the diagnosis will be upgraded to severe aortic valve stenosis.¹¹¹ The impedance of left ventricular ejection into the aorta results in increased left ventricular systolic pressure, left ventricular hypertrophy, and eventually left ventricular dilation. When symptoms such as angina, dyspnea, syncope, and other indicators of heart failure develop, it is critical to intervene to prevent further damage to the left ventricle. Aortic valve replacement is usually indicated. Balloon valvotomy (dilation) may be an option for carefully selected patients with aortic stenosis without calcification, or for patients whose mortality risk during surgical aortic valve replacement is unacceptably high.^111,112

Aortic regurgitation, also known as aortic insufficiency, can occur as a result of rheumatic fever, systemic hypertension, Marfan syndrome, syphilis, rheumatoid arthritis, aging valve tissue, or discrete subaortic stenosis (see Table 12-8, D). Aortic valve incompetence results in a reflux of blood back into the left ventricle during ventricular diastole. To accommodate this extra volume, the left ventricle initially dilates and then hypertrophies in an attempt to empty more completely and to meet the needs of the peripheral circulation. Aortic valve replacement is recommended for symptomatic patients with well-preserved or moderate left ventricular dysfunction.¹¹¹

Tricuspid valve stenosis is rarely an isolated lesion (see Table 12-8, E). It often occurs in conjunction with mitral or aortic disease. Its origin most often is rheumatic fever or a complication of intravenous drug abuse and resultant endocarditis.¹¹¹ Tricuspid valve stenosis increases the pressure work of the usually low-pressure right atrium, resulting in right atrial hypertrophy. The right atrium dilates in an attempt to accommodate the residual right atrial volume and the incoming venous return. As a result, systemic venous congestion occurs—the consequences of which include jugular venous congestion, liver failure, hepatomegaly, ascites, and peripheral edema.

Tricuspid valve regurgitation usually results from advanced failure of the left side of the heart that eventually affects the right side of the heart, severe pulmonary hypertension, or as a complication of infectious endocarditis111 (see Table 12-8, F).

Education for the patient with acute or chronic heart failure caused by valvular dysfunction includes: (1) information related to diet, (2) fluid restrictions, (3) the actions and side effects of heart failure medications, (4) the need for prophylactic antibiotics before undergoing any invasive procedures such as dental work, and (5) when to call the health care provider to report a negative change in cardiac symptoms. Many patients also require information about valvular heart surgery. Achieving the optimal outcomes for the patient with valve disease requires contributions from a team of educated health care clinicians. Collaborative multidisciplinary priorities are listed in the box Evidence-Based Collaborative Practice: Valvular Heart Disease. The heart valve replacement section in Chapter 13 provides more information on surgical management.