An over-stretched heart is the result of cardiac muscle damage of any sort, most often due to coronary heart disease (blockage of the arteries supplying blood to the heart itself), but it can also be the result of abnormal valves
and, more rarely, the toxic effects of
alcohol or infection on the cardiac muscle (cardiomyopathy).
Most drug related sudden cardiac deaths are due to an arrhythmia caused by the drugs, not en enlarged heart.