Chapter 24. The Cardiomyopathies, Myocarditis, and Pericardial Disease

Cardiomyopathies are the third most common form of heart disease in the United States and are the second most common cause of sudden death in the adolescent population. It is a disease process that directly affects the cardiac structure and alters myocardial function. Four types are currently recognized: (a) dilated cardiomyopathy (DCM), (b) hypertrophic cardiomyopathy (HCM), (c) restrictive cardiomyopathy, and (d) dysrhythmogenicity of right ventricular cardiomyopathy.

Dilation and compensatory hypertrophy of the myocardium result in depressed systolic function and pump failure leading to low cardiac output. Eighty percent of cases of DCM are idiopathic. Idiopathic DCM is the primary indication for cardiac transplant in the United States.

Clinical Features

Systolic pump failure leads to signs and symptoms of congestive heart failure (CHF) including dyspnea on exertion, orthopnea, and paroxysmal nocturnal dyspnea. Chest pain due to limited coronary vascular reserve also may be present. Mural thrombi can form from diminished ventricular contractile force, and there may be signs of peripheral embolization (eg, focal neurologic deficit, flank pain, hematuria, or pulseless, cyanotic extremity). Holosystolic regurgitant murmur of the tricuspid and mitral valve may be heard along the lower left sternal border or at the apex. Other findings include a summation gallop, an enlarged and pulsatile liver, bibasilar rales, and dependent edema.

Diagnosis and Differential

Chest x-ray usually shows an enlarged cardiac silhouette, biventricular enlargement, and pulmonary vascular congestion (“cephalization” of flow and enlarged hila). The electrocardiogram (ECG) shows left ventricular hypertrophy, left atrial enlargement, Q or QS waves, and poor R wave progression across the precordium. Echocardiography confirms the diagnosis and demonstrates ventricular enlargement, increased systolic and diastolic volumes, and a decreased ejection fraction. Differential diagnosis includes acute myocardial infarction, restrictive pericarditis, acute valvular disruption, sepsis, or any other condition that results in a low cardiac output state.

Emergency Department Care and Disposition

Patients with newly diagnosed, symptomatic DCM require admission to a monitored bed or intensive care unit. Initial management is directed by symptoms.

1. Intravenous access, supplemental oxygen, and continuous monitoring should be established.

2. Intravenous diuretics (eg, furosemide 40 milligrams IV) and digoxin (maximum dose, 0.5 milligram IV) may improve symptoms.

3. Angiotensin-converting enzyme (ACE) inhibitors, such as enalaprilat 1.25 milligrams IV every 6 hours, and the β-blocker carvedilol, 3.125 milligrams orally, improve survival long term.

4. Amiodarone (loaded 150 milligrams IV over 10 min and then 1 milligrams/min for 6 hours) for complex ventricular ectopy can be administered.

5. Anticoagulation should be considered to reduce risk of mural thrombus formation.

Patients with mild to moderate exacerbation of symptoms can be managed with intravenous diuretics, reinstitution of their medications if noncompliant, counseling, and prompt follow-up.

It is important to search for other causes of exacerbations of DCM such as myocardial ischemia or infarction, anemia, infection, new-onset atrial ...