DEFINITION AND CLASSIFICATION
Cardiomyopathy is disease of the heart muscle. It is estimated that cardiomyopathy accounts for 5–10% of the heart failure in the 5–6 million patients carrying that diagnosis 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 attributed to multivessel coronary artery disease, and nonischemic cardiomyopathy to describe cardiomyopathy from other causes. As of 2013, cardiomyopathies are defined as “disorders characterized by morphologically and functionally abnormal myocardium in the absence of any other disease that is sufficient, by itself, to cause the observed phenotype.” It was further specified that many cardiomyopathies will be attributable to genetic disease.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 254-1).
TABLE 254-1Presentation with Symptomatic Cardiomyopathy |Favorite Table|Download (.pdf) TABLE 254-1 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, may also be primarily affected ||Increased; may be massive ||Increased; related to elevated filling pressures |
|Valvular regurgitation ||Related to annular dilation; mitral appears earlier during decompensation; tricuspid regurgitation with right ventricular dysfunction ||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, may have dominant right-sided symptoms ||Exertional intolerance; may have chest pain |
|Congestive symptomsa ||Left before right, except right prominent in young adults ||Right often dominates ||Left-sided congestion at rest may develop late |
|Arrhythmias ||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 ...