What is cardiomyopathy?
Cardiomyopathy is an alteration in the function of the heart muscle. It can occur for several reasons in cats and it can take several forms. When the muscle is sufficiently affected that it can not function properly, heart failure occurs. Cardiomyopathy is the deterioration of the cardiac muscle of the heart wall. Cardiomyopathies can generally be categorized into two groups:
ischemic cardiomyopathy and nonischemic cardiomyopathy.
Nonischemic cardiomyopathy is weakness in the muscle of the heart that is not due to coronary artery disease. To make a diagnosis of nonischemic cardiomyopathy, significant coronary artery disease should be ruled out. The term nonischemic cardiomyopathy does not describe the etiology of weakened heart muscle. The nonischemic cardiomyopathies are a mixed-bag of disease states, each with their own causes.
Nonischemic cardiomyopathy has a number of causes including drug and alcohol toxicity, certain infections, and various genetic and idiopathic (i.e. unknown) causes. There are four main types of nonischemic cardiomyopathy: dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM or HOCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), restrictive cardiomyopathy (RCM).
Cardiomyopathy can lead to heart failure as the pumping efficiency of the heart is diminished. People with cardiomyopathy are often at risk of arrhythmia and/or sudden cardiac death.
Dilated cardiomyopathy (DCM) is the commonest form of cardiomyopathy, and one of the leading indications for heart transplantation. In DCM the heart (especially the left ventricle) is enlarged and weakened. Approximately 40% of cases are familial, but the genetics are poorly understood compared with HCM.
Hypertrophic cardiomyopathy (HCM) is a genetic disorder caused by various mutations in genes encoding sarcomeric proteins. In HCM the heart muscle is thickened, which can obstruct blood flow and prevent the heart from functioning properly.
Arrhythmogenic right ventricular cardiomyopathy (ARVC) arises from an electrical disturbance of the heart in which heart muscle is replaced by fibrous scar tissue. The right ventricle is generally most affected.
Restrictive cardiomyopathy (RCM) is the least common cardiomyopathy. The walls of the ventricles are stiff, but may not be thickened, and resist the normal filling of the heart with blood.
A rare form of restrictive cardiomyopathy is the obliterative cardiomyopathy, seen in the hypereosinophilic syndrome. In this type of cardiomyopathy, the myocardium in the apicies of the left and right ventricles become thickened and fibrotic, causing a decrease in the volumes of the ventricles and a type of restrictive cardiomyopathy.