Chapter 117: Cardiomyopathies and Myocarditis

Cardiomyopathies are primary diseases of heart muscle. Table 117-1 summarizes distinguishing presenting features of the three major types of cardiomyopathy (CMP). Table 117-2 details the comprehensive initial evaluation of suspected cardiomyopathies.

TABLE 117-1: Presentation with Symptomatic Cardiomyopathy
	DILATED	RESTRICTIVE	HYPERTROPHIC
Ejection fraction (normal >55%)	Usually <30% when symptoms severe	25–50%	>60%
Left ventricular diastolic dimension (normal <55 mm)	≥60 mm	<60 mm (may be decreased)	Often decreased
Left ventricular wall thickness	Normal or decreased	Normal or increased	Markedly increased
Atrial size	Increased	Increased; may be massive	Increased
Valvular regurgitation	Related to annular dilation	Related to endocardial involvement; frequent mitral and tricuspid regurgitation, rarely severe	Related to valve-septum interaction: mitral regurgitation
Common first symptoms	Exertional intolerance	Exertional intolerance, fluid retention early	Exertional intolerance; may have chest pain
Congestive symptoms^a	Left before right, except right prominent in young adults	Right often dominates	Left-sided congestion may develop late
Arrhythmia	Ventricular tachyarrhythmia; conduction block in Chagas’ disease, and some familial forms. Atrial fibrillation	Ventricular uncommon except in sarcoidosis, conduction block in sarcoidosis and amyloidosis. Atrial fibrillation	Ventricular tachyarrhythmias; atrial fibrillation

^aLeft-sided symptoms of pulmonary congestion: dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea. Right-sided symptoms of systemic venous congestion: hepatic and abdominal distention, discomfort on bending, peripheral edema.

TABLE 117-2: Initial Evaluation of Cardiomyopathy
Clinical Evaluation
Thorough history and physical examination to identify cardiac and noncardiac disorders^a Detailed family history of heart failure, cardiomyopathy, skeletal myopathy, conduction disorders and tachyarrhythmias, sudden death History of alcohol, illicit drugs, chemotherapy, or radiation therapy^a Assessment of ability to perform routine and desired activities^a Assessment of volume status, orthostatic blood pressure, body mass index^a
Laboratory Evaluation
Electrocardiogram^a Chest radiograph^a Two-dimensional and Doppler echocardiogram^a Magnetic resonance imaging to assess myocardial inflammation and fibrosis Chemistry: Serum sodium,^a potassium,^a calcium,^a magnesium^a Fasting glucose (glycohemoglobin in diabetes mellitus) Creatinine,^a blood urea nitrogen^a Albumin,^a total protein,^a liver function tests^a Lipid profile Thyroid-stimulating hormone^a Serum iron, transferrin saturation Urinalysis Creatine kinase isoforms Cardiac troponin Hematology: Hemoglobin/hematocrit^a White blood cell count with differential,^a including eosinophils Erythrocyte sedimentation rate
Initial Evaluation When Specific Diagnoses Are Suspected
DNA sequencing for genetic disease; panel selection based on phenotype Titers for infection in presence of clinical suspicion: Acute viral (e.g., coxsackievirus, echovirus, influenza) Human immunodeficiency virus Chagas’ disease, Lyme disease, toxoplasmosis Coronary angiography in pts with angina who are candidates for intervention^a Serologies for active rheumatologic disease Endomyocardial biopsy including sample for electron microscopy when suspecting specific diagnosis with therapeutic implications Screening for sleep-disordered breathing

^aLevel I Recommendations from ACC/AHA Practice Guidelines for Chronic Heart Failure in the adult.

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