Which type of cardiomyopathy involves dilated ventricles with decreased contractility?

Dilated cardiomyopathy is characterized by the dilation of the heart ventricles leading to impaired contractility. This condition typically results in the heart's ability to pump blood effectively being compromised due to the enlarged (dilated) ventricles. The structural changes in the heart muscle lead to a decreased ejection fraction, meaning that less blood is pumped out of the heart with each contraction. Symptoms often include heart failure and decreased exercise tolerance, among others.

In contrast, hypertrophic cardiomyopathy involves thickened heart muscle that can obstruct blood flow, thereby not primarily affecting dilation. Restrictive cardiomyopathy features stiff ventricular walls that limit the heart's ability to fill properly, which is different from the dilation seen in dilated cardiomyopathy. Arrhythmogenic right ventricular cardiomyopathy, on the other hand, primarily affects the right ventricle and involves the replacement of myocardial tissue with fatty or fibrous tissue, impacting the heart's electrical conduction and sometimes leading to arrhythmias rather than purely contractility.

Thus, the distinction lies in the hallmark of dilated cardiomyopathy where it is the dilation of the ventricles coupled with decreased contractility that defines this condition.