DEFINITION AND CLASSIFICATION
Cardiomyopathy is a disease of the heart muscle. It is estimated that cardiomyopathy accounts for 5–10% of the 5–6 million patients already diagnosed with heart failure in the United States. This term is intended to exclude cardiac dysfunction that results from other structural heart disease, such as coronary artery disease, primary valve disease, or severe hypertension; however, in general usage the phrase ischemic cardiomyopathy is sometimes applied to describe diffuse dysfunction occurring in the presence of multivessel coronary artery disease, and nonischemic cardiomyopathy to describe cardiomyopathy from other causes. As of 2006, cardiomyopathies are defined as “a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that usually (but not invariably) exhibit inappropriate ventricular hypertrophy or dilatation and are due to a variety of causes that frequently are genetic.”1
The traditional classification of cardiomyopathies into a triad of dilated, restrictive, and hypertrophic was based initially on autopsy specimens and later on echocardiographic findings. Dilated and hypertrophic cardiomyopathies can be distinguished on the basis of left ventricular wall thickness and cavity dimension; however, restrictive cardiomyopathy can have variably increased wall thickness and chamber dimensions that range from reduced to slightly increased, with prominent atrial enlargement. Restrictive cardiomyopathy is now defined more on the basis of abnormal diastolic function, which is also present but initially less prominent in dilated and hypertrophic cardiomyopathy. Restrictive cardiomyopathy can overlap in presentation, gross morphology, and etiology with both hypertrophic and dilated cardiomyopathies (Table 21-1).
TABLE 21-1PRESENTATION WITH SYMPTOMATIC CARDIOMYOPATHY |Favorite Table|Download (.pdf) TABLE 21-1PRESENTATION 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 ||Decreased ||Normal or increased ||Markedly increased|
|Atrial size ||Increased ||Increased; may be massive ||Increased; related to abnormal|
|Valvular regurgitation ||Related to annular dilation; mitral appears earlier, during decompensation; tricuspid regurgitation in late stages ||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 symptomsa ||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 families; atrial fibrillation. ||Ventricular uncommon except in sarcoidosis conduction block in sarcoidosis and amyloidosis; atrial fibrillation. ||Ventricular tachyarrhythmias; atrial fibrillation|
Expanding information renders this classification triad based on phenotype increasingly inadequate to define disease or therapy. Identification of more genetic determinants of cardiomyopathy has suggested a four-way classification scheme of etiology as primary (affecting primarily the heart) and secondary to other systemic disease. The primary ...