Severe Heart Failure

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82 Severe Heart Failure

Heart failure is a very common condition with high mortality and morbidity rates. Data from the Framingham heart study suggest that at 40 years of age, the lifetime risk for congestive heart failure is 21.0% (95% confidence interval [CI], 18.7%-23.2%) for men and 20.3% (95% CI, 18.2%-22.5%) for women.1 The prevalence of heart failure is between 2% and 3% and reaches 10% and 20% in those older than 70 years.2 In the United States, approximately 5 million patients have heart failure, with over 550,000 new cases diagnosed each year.3 Despite improvements in treatment, the overall prevalence of heart failure is increasing because of the aging of the population and better survival following myocardial infarction (MI).3,4 Total heart failure–related costs were about $28 billion in 2005 and consume approximately 2% of national expenditure on health in Europe.5 Patients with severe heart failure often present in extremis, and their condition may deteriorate rapidly, so a sound knowledge of immediate treatment is vital for critical care and emergency physicians. Such patients often respond rapidly to appropriate treatment, making this a very satisfying condition to treat. However, it is important to note that outlook remains poor despite initial clinical improvement.

In this chapter, we will discuss causes, presentation, investigation, treatment, and prognosis of severe heart failure, including new developments in the investigation and management of this common, serious condition.

image Etiology

Ischemic heart disease is the most common cause of heart failure, commonly related to previous MI. Although epidemiologic surveys such as the Framingham study suggest a high prevalence of hypertension as the “cause” of heart failure, it is likely that associated ischemic heart disease or arrhythmias also contribute. Other studies have demonstrated similar findings (Table-82-1).

It should be pointed out that epidemiologic studies such as the Framingham study have been almost exclusively carried out in white populations, and etiologic factors may have different relative importance in other ethnic groups. For example, in Afro-Caribbeans, hypertension is the predominant etiologic factor, whereas in Indo-Asians, coronary artery disease and diabetes are common. It is important to note that different causes may coexist in the same patient.

Ischemic Heart Disease

Ischemic heart disease is the most common cause of heart failure in the Western world. Many patients presenting with severe heart failure will give a history of previous MI. However, an episode of severe heart failure may also be the first manifestation of ischemic heart disease, either due to massive MI causing cardiogenic shock6 or as a result of previous silent (or unreported) episodes of ischemia/infarction. It is therefore important to exclude MI in all patients presenting with severe heart failure. Additionally, once the patient is stabilized, adequate secondary preventive strategies are vital to prevent further ischemia or infarction. Some patients with ischemic cardiomyopathy may show evidence of “hibernation” of segments of myocardium,7 and cardiac function in these patients may improve with revascularization (see later discussion).

Dilated Cardiomyopathy

Dilated cardiomyopathy is defined as left ventricular dysfunction of unknown cause. It is therefore a diagnosis of exclusion, and a firm diagnosis of dilated cardiomyopathy can only be made in the presence of a normal coronary angiogram. Intensive investigation of patients with a label of dilated cardiomyopathy may yield a definite cause in at least 50% of cases (Table 82-2). As many as 30% of patients with dilated cardiomyopathy may have a genetic cause of the disease.8

TABLE 82-2 Final Diagnoses in 1230 Patients with Initially Unexplained Cardiomyopathy

Diagnosis Number Percentage
Idiopathic dilated cardiomyopathy 616 50
Myocarditis 111 9
Ischemic heart disease 91 7
Infiltrative cardiomyopathy 59 5
Peripartum cardiomyopathy 51 4
Hypertension 49 4
Human immunodeficiency virus infection 45 4
Connective tissue disease 39 3
Substance abuse 37 3
Familial 25 2
Valvular disease 19 1.5
Doxorubicin therapy 15 1
Endocrine disorder 11 1
Others 62 5.5

Data from Felker GM et al. Underlying causes and long term survival in patients with initially unexplained cardiomyopathy. N Engl J Med 2000;342:1077-84.

Dilated cardiomyopathy can manifest at any age, and because heart failure may be perceived as a disease of the elderly, this can often result in misdiagnosis in younger patients.

Diabetes

In addition to the role of diabetes as a risk factor for the development of ischemic heart disease and resultant heart failure, there is evidence for a distinct diabetic cardiomyopathy.8 Current guidelines recognize diabetes as a risk factor for heart failure.8 Hemoglobin A1c levels have been shown to be an independent progressive risk factor for cardiovascular and total mortality and rehospitalization rate in heart failure patients.9,10 All patients presenting with heart failure should be screened for diabetes, both for this reason and so that appropriate secondary prevention can be instituted.

Other Possible Causes or Exacerbating Factors

Rare causes of heart failure must always be considered, especially in younger patients, and these include amyloidosis and hemochromatosis. Another important cause is human immunodeficiency virus (HIV) infection, and HIV-associated cardiomyopathy has been well described. Given that HIV infection is considered pandemic by the World Health Organization, many more patients may present in this way in the future.

Patients with a long history of stable heart failure may decompensate as the result of a number of different factors. Intercurrent infection is a common cause of decompensation, and prompt recognition and treatment are important. Arrhythmias are also a common cause for decompensation of a previously stable heart failure patient, and a recent meta-analyses of 16 randomized clinical trials (53,969 patients) revealed that the presence of AF is associated with an adverse effect on total mortality, with an odds ratio of 1.40 (95% CI, 1.32-1.48).11 Another common cause of decompensation is anemia, which is often poorly tolerated in patients with heart failure. A meta-analysis of 34 studies comprising 153,180 patients, of whom 37.2% were anemic, showed that adjusted mortality risk of anemia had a hazard ratio of 1.46 (95% CI, 1.26-1.69).12 Poor prognosis associated with presence of atrial fibrillation or anemia was irrespective of left ventricular systolic function, either preserved or impaired.11,12 It is vital to consider and treat such exacerbating conditions where appropriate.

image Presentations of Severe Heart Failure

Severe heart failure can manifest in several ways. The patient may or may not have a previous history of heart failure or precipitating conditions such as angina or hypertension. It is important to note that gradual-onset heart failure can easily be mistaken for asthma, and patients presenting to an emergency department may well have been given a diagnosis of asthma in the weeks or months preceding their admission.

Acute Presentation: Pulmonary Edema

The classic presentation of heart failure is with acute pulmonary edema. Such patients present with extreme shortness of breath, often unable to speak because of their rapid respiratory rate. Symptoms may come on very suddenly. Even patients with ischemic heart failure may not report chest pain, either because the ischemia is silent or because the pain is being masked by the profound shortness of breath. Many patients will be unable to give a history owing to their shortness of breath, and therefore examination findings and basic investigations are vital to make the diagnosis.

Cardiovascular Examination

Examination of the pulse may reveal atrial fibrillation. Patients in sinus rhythm are usually tachycardic, although patients with a history of ischemic heart disease may well be taking beta-blockers, which mask tachycardia. Heart rate appears to be an independent and powerful factor of prognosis in heart failure. In the BEAUTIFUL study, heart failure patients with heart rates of 70 bpm or greater had 34% higher risk for cardiovascular death and 53% higher risk admission to hospital than those with heart rate blow 70 bpm. The study has shown 8% and 15% increments of cardiovascular death and hospital admission for every increase of 5 bpm.13

The blood pressure is preserved in approximately 80% of patients presenting with decompensated heart failure overall, but a significant number are hypotensive at presentation. This is the single most important factor affecting treatment (see later discussion) and is also likely to be altered by treatment, and so must be measured frequently. Palpation may or may not reveal a displaced apex beat, depending on the length of the history. There may be palpable heaves or thrills, but these are likely to be difficult to appreciate in the acutely breathless patient. Auscultation of the heart sounds may well be difficult. There may be a third or fourth heart sound, or there may be murmurs representing chronic stenotic or regurgitant valves, or an acute mitral valve prolapse or ventricular septal defect following MI. (These latter two conditions can even occur several days after admission in a patient with extensive MI.) It is important to reexamine the patient regularly; once initial treatment has commenced, the patient may become less breathless, and previously inaudible signs may become clear.

Subacute Presentation: Shortness of Breath/Peripheral Edema

Many patients with severe heart failure present less acutely with varying combinations of breathlessness and edema. This is often the case in patients with a previous diagnosis of heart failure and can be precipitated by intercurrent infection or withdrawal of diuretic or other medication (by the patient or a physician). In the early stages, edema may be more prominent unilaterally, and this may result in diagnostic difficulty. Such patients may be referred for exclusion of deep venous thrombosis (and it is important to be aware that the two conditions can coexist). These patients often report gradually increasing breathlessness with symptoms of orthopnea (shortness of breath occurring when lying supine) and paroxysmal nocturnal dyspnea (sudden shortness of breath waking the patient from sleep). Patients may resort to sleeping in a chair, leading to additional gravitational edema. Edema of the bowel can lead to reduced appetite, so called “cardiac cachexia,” and further edema from hypoproteinemia. Peripheral edema is therefore often multifactorial in patients with heart failure. Differential diagnoses of peripheral edema are listed in Table 82-3.

TABLE 82-3 Causes of Peripheral Edema

Examination findings are similar to those for the acute presentation, although the patient is not in extremis and is able to speak sufficiently to give a full history. A full examination is possible more often in this situation, including auscultation of the heart sounds and abdominal examination. Peripheral edema may well be extensive, up to the abdominal wall and sacral areas. The jugular venous pulse may be elevated. Patients with extensive peripheral edema but a low jugular venous pulse may have hypoproteinemia rather than heart failure.

image Investigations

Electrocardiography

All patients presenting with severe heart failure require at least one electrocardiogram (ECG). In cases of diagnostic difficulty, an entirely normal ECG virtually excludes systolic heart failure as the cause of symptoms.14 In heart failure, an ECG is essential to diagnose arrhythmias such as atrial fibrillation, which may complicate management, as well as to look for evidence of myocardial ischemia or infarction and conduction abnormalities such as left bundle branch block or bradycardia due to high-degree atrioventricular block, which may respond to pacing. In patients in whom ischemia is suspected, serial ECGs are recommended, as changes may evolve during the course of the patient’s treatment. Patients with acute severe heart failure should have continuous ECG monitoring during the acute phase, as they are at high risk for malignant ventricular arrhythmias. Patients with biventricular pacemakers (discussed later) in situ may have paced QRS complexes that are narrower than in those with single-chamber right ventricular leads.

Echocardiography

Echocardiography should be carried out early in all cases of suspected heart failure. In recent years, bedside echocardiography devices have been developed that can be useful in the emergency department to assess the left ventricle and valves initially. In all cases, a full echocardiogram should be carried out when the patient is sufficiently stabilized.

Echocardiography is useful both to determine the extent of left ventricular dysfunction and to identify the cause. In cases of ischemic cardiomyopathy, regional wall motion abnormalities are commonly seen (although these can occasionally occur in cases of cardiomyopathy of other causes). Valve disease is readily identified by echocardiography. Echocardiography can be used to calculate the left ventricular ejection fraction, but in experienced hands, a qualitative assessment of left ventricular function can be equally useful. Some patients presenting with severe heart failure have preserved systolic function, and echocardiography can also be used to assess diastolic function. In the patient presenting with shortness of breath, in whom the cause is unclear, echocardiography can readily determine the presence or absence of systolic heart failure. Although a number of diagnostic criteria have been developed for assessment of the diastolic left ventricular function, their reliability in predicting intracardiac filling pressures is not always satisfactory and needs further development.15 A clear distinction can sometimes be made only by measurements of gas exchange or blood oxygen saturation or by invasive hemodynamic measurements during graded levels of exercise following the clinical stabilization.

It is important to emphasize that heart failure is not directly equivalent to the impairment of left ventricular contractility, and there is a poor correlation between parameters of myocardial function and the symptoms. About half of heart failure patients have preserved contractility. However, prognosis for patients presenting with symptomatic heart failure is equally poor for those with normal or decreased ejection fraction.

Brain Natriuretic Peptide

Natriuretic peptides are currently emerging as a novel test in cases of heart failure. The group includes three structurally related peptides, with variable activity at three distinct natriuretic peptide receptor subtypes, of which two are of potential use in patients with heart failure. Atrial natriuretic peptide is released from the atria in response to wall stretch. Brain natriuretic peptide (BNP), so called because it was first identified in brain tissue, is mainly released by the cardiac ventricles in response to wall stretch.16 All the natriuretic peptides are elevated in acute coronary syndromes and MI, owing to release from myocytes. In addition, decompensated heart failure is associated with elevations of natriuretic peptide levels. Many possible applications for assays of these peptides have been proposed, but at present the most widely accepted indications for use of BNP (which appears to have the best sensitivity/specificity of all the natriuretic peptides) are as follows:

The use of BNP for monitoring progress in heart failure is controversial; some studies have suggested that BNP may be useful to guide treatment. Indeed, many studies have found that BNP levels may have prognostic implications. It is also important to note that BNP levels must be used in conjunction with clinical assessment of the patient, as unexpected values may occur in some patients, such as a high BNP level in a stable patient. Recent findings do not support routine use of the peptides in all dyspneic patients admitted to the emergency department.17

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