The word dilated means enlarged, Dilated Cardiomyopathy is thus an enlarged heart, this is caused by weakening of the heart muscle.
Dilated cardiomyopathy may be caused by an earlier heart attack, part of the heart muscle may have died due to a lack of blood and oxygen, this weakens the rest of the muscle and it enlarges (ischemic cardiomyopathy) with time.
Symptoms may include; shortness of breath with activity, sudden shortness of breath at night (paroxysmal nocturnal), difficulty sleeping, fainting (syncope), collection of fluid in feet and legs, fatigue and palpitations. Severe arrhythmia can cause palpitations that may lead to syncope and possible sudden death.
More information is available at the British Heart Foundation