In dilated cardiomyopathy (DCM), the heart muscle weakens and the heart becomes enlarged. As the heart becomes stretched, its lower chambers (the ventricles) are less able to pump blood efficiently. Eventually, the heart isn’t able to pump enough blood to the body, and the lungs become congested. This condition is called heart failure. Abnormal heart rhythms may also result when the heart becomes enlarged.
DCM can have several causes. One of the most common situations is after a viral infection that results in inflammation of the heart (myocarditis). In response to the infection, the body turns against its own heart muscle. It’s not known why the viral infection affects the hearts of some people but not most others. Some babies may be born with a weak heart due to an illness suffered by the mother, and some people with muscular dystrophy or mitochondrial disorders may develop progressive weakening of the heart. Also, some people have genetic mutations from birth that can cause the heart muscle to function improperly. Routine cardiac evaluation is necessary to detect this decline in heart function since symptoms may develop later, after the heart is severely weakened. Exposure to toxins, such as some kinds of chemotherapy used to treat cancers, can also result in DCM. Sometimes, this becomes evident years after the treatment has occurred. While not as common in children, HIV infection can also result in DCM.