DEFINITION AND CLASSIFICATION
Cardiomyopathy is disease of the heart muscle. It is estimated that cardiomyopathy accounts for 5 – 1 0 % of the heart failure in the 5-6 million patients carrying that diagnosis in the United States. This term is intended to exclude cardiac dy巾nction that results from other structural heart disease, such as coronary arterγ disease, primary valve disease, or severe hypertension;
See the following table of, Major Causes of Dilated Cardiomyopathy with Common Examples.
An enlarged left ventricle with decreased systolic function as measured by left ventricular ejection fraction characterizes dilated cardiomyopathy . Systolic failure is more marked than diastolic dysfunction. Although the syndrome of dilated cardiomyopathy has multiple etiologies (Table 287-4)， there appear to be common pathways of secondary response and disease progression When myocardial i时ury is aιquired， some myocytes may die initial1y， whereas oiliers survive only to have later programmed cell death (apoptosis)， and remaining myocytes hypertrophy in response to increased wal1 stress. Local and circulating factors stimulate deleterious seιondary responses that contribute to progression of disease. D严lamic remodeling of the interstitial scaffolding affects diastolic function and the amount of ventricular dilation. Mitral regurgitation commonly develops as the valvular apparatus is distorted and is usually substantial by the time heart failure is severe. Many cases that present “acuteiy” have progressed silentiy through these stages over months to years. Dilation and decreased function of the right ventricle may result from the initial injurγ and occasionally dominate， but more commonly appear later in relation to mechanical interactions with the failing left ventricle and the elevated after!oad presented by seιondary pulmonary hypertension.