In dilated cardiomyopathy, the heart muscle becomes stretched and thin. The ventricles then enlarge (dilate) because their muscular walls have become weak and floppy. This means the heart does not pump blood as strongly as normal. These changes often start in the left ventricle (the part of the heart which pumps blood around most of the body), and can then later affect the right ventricle (which pumps blood to the lungs) and the atria (the parts of the heart that receive blood from the veins).
This is a companion discussion topic for the original article at https://patient.info/heart-health/dilated-cardiomyopathy