A friend has been diagnosed as having his heart so enlarged now as to be " twice its normal size" (his words ). What is the mechanism by which the heart is enlarged; is it increased muscle, fat, other tissue, dilation or what?What are the causes of the effect ? (This man has been a cocaine user for example; is that a possible cause ? )

Enlarged heart (cardiomegaly) is most often dilated cardiomyopathy where the pumping function of the heart is impaired, leading to dilation of the ventricles, which make up the major portion of the heart. The chambers of the heart are stretched, enlarging the interior volume while thinning out the walls. There are many causes (too numerous to mention here) including coronary artery disease and drug effects such as chronic cocaine or alcohol abuse. It is commonly associated with a condition known as congestive heart failure.

The other common cause of enlarged heart is myocardial hypertrophy. Here there is additional bulk of heart muscle in the heart's walls, without necessarily involving enlargement of the interior chamber volume. This is often associated with high blood pressure.

Infiltration of heart muscle with other kinds of tissue, including fat, is another variety of "enlarged heart," though less common than the other two.

Enlarged heart is a complex medical topic. Your friend should of course consult with a cardiologist if he has not already done so. The condition is sometimes reversible, especially if caused by cocaine toxicity. Good luck to him!

Thans Professor. We think that he has been, may still be, a heavy cocaine user.In that event from what you say the condition may respond to treatment,which is good news. Of course, getting him to understand that and getting some appropriate response is out of the hands of his friends and advisers. I shall not even try, because any ex-addict of anything (mine was alcohol) knows better than to waste their breath