Chapter 16 Congestive Heart Failure
PATHOPHYSIOLOGY
Congestive heart failure (CHF) occurs when the heart cannot pump the blood returning to the right side of the heart, provide adequate circulation to meet the needs of organs and tissues in the body, or a combination of the two. The component factors in CHF include preload and circulating volume, afterload, and contractility. Causes include congenital and acquired heart diseases with pressure and/or volume overload, and myocardial insufficiency.
1. Congenital heart disease with pressure or volume overload is a common cause of CHF in pediatric patients. The timing of onset varies fairly predictably with the type of defect (Table 16-1). It is important to note the following:
2. Acquired heart disease of various etiologies can result in CHF. The age of onset of CHF is less predictable with acquired heart disease than with congenital heart disease; however, there are some general considerations:
Table 16-1 Causes of Congestive Heart Failure Due to Congenital Heart Disease According to the Time of Occurrence
| Age or Time of Occurrence | Cause |
|---|---|
| At birth | a. HLHS |
| b. Volume overload lesions (e.g., severe TR or PR, large systemic AV fistula) | |
| First week | a. TGA |
| b. PDA in small premature infants | |
| c. HLHS (with more favorable anatomy) | |
| d. TAPVR, particularly those with pulmonary venous obstruction | |
| 1–4 weeks | a. COA (with associated anomalies) |
| b. Critical AS | |
| c. Large L-R shunt lesions (e.g., VSD, PDA) in premature infants | |
| d. All other lesions listed above | |
| 4–6 weeks | a. Some L-R shunt lesions, such as ECD |
| 6 weeks to 4 months | a. Large VSD |
| b. Large PDA | |
| c. Others: anomalous left coronary artery from PA |
AS, Aortic stenosis; AV, arteriovenous; COA, coarctation of the aorta; ECD, endocardial cushion defect; HLHS, hypoplastic left heart syndrome; L-R, left to right; PA, pulmonary artery; PDA, patent ductus arteriosus; PR, pulmonary regurgitation; PS, pulmonary stenosis; TAPVR, total anomalies pulmonary venous return; TGA, transposition of the great arteries; TR, tricuspid regurgitation; VSD, ventricular septal defect.
Reprinted with permission from Park MK: The pediatric cardiology handbook, St. Louis, 2003, Mosby.
If the heart fails for any reason and cardiac output is not sufficient to meet the metabolic needs of the body, the sympathetic nervous system responds by trying to increase circulating blood volume by diverting blood from nonessential organs. This decreases renal blood flow, activates the renin-angiotensin-aldosterone mechanism, and increases sodium and water retention. Catecholamine release with decreased cardiac output causes increased heart rate, increased vascular tone, and sweating. These initial compensatory mechanisms for maintaining cardiac output (increased circulating blood volume, increased heart rate, and vascular tone) eventually lead to clinical manifestations of CHF.
LABORATORY AND DIAGNOSTIC TESTS
Diagnosis is made on the basis of physical examination revealing signs and symptoms previously noted. The following can assist in further evaluation:
1. Electrocardiogram (ECG)—for diagnosis of tachycardia or bradycardia arrhythmias, may be helpful in determining type of defect; is not helpful in determining presence of CHG.
2. Chest radiographic study—heart will be enlarged, and pulmonary infiltrates will be present. Children with large left-to-right shunts have cardiomegaly without CHF.
3. Echocardiogram—may confirm enlarged heart chamber(s) and/or impaired left ventricular (LV) function. Useful in determining cause of CHF and in ongoing evaluation of efficacy of therapy.
MEDICAL MANAGEMENT
The initial management of CHF is accomplished by the use of pharmacologic agents that act to improve the function of the heart muscle and/or reduce the workload on the heart. Digitalis is given to increase cardiac output by slowing conduction through the atrioventricular node and make each contraction stronger. Diuretics decrease preload volume because their actions result in decreased extracellular fluid volume. Venous, arterial, and mixed dilators may be given to decrease preload volume by reducing systemic or pulmonary vascular resistance. Fluids are usually restricted to two thirds of maintenance levels, and attention is given to nutrition and rest. Medical management continues with the plan for interventional cardiac cath-eterization or surgical intervention, if indicated.
NURSING INTERVENTIONS
2. Promote oxygenation and ventilation.
3. Provide rest and comfort measures.
4. Promote and maintain child’s fluid and electrolyte balance.
5. Promote child’s nutritional status.
6. Assist family in understanding, accepting, and working through emotions of having a child with a chronic condition.
Discharge Planning and Home Care
1. Educate on specific condition.
2. Provide specific instructions about medications and adverse effects.
3. Although caregivers of infants with chronic CHF are usually quite skilled in assessing for signs and symptoms of CHF, reinforce as necessary.
4. Instruct in feeding techniques and nutritional requirements.
5. Refer as indicated to infant stimulation programs or parent support groups.
