Well like muskate said the heart is a muscle and if you use steroids they are not selective on the types of skelital muscle they affect. In a sense they are selective as they don't cause hypertrophy of smooth muscle which lines our veins/arteries and GI tract at least not to any degree that is pathological. So when taking anabolics and working out for many years the anabolic effect of the steroids can certainly cause the muscle tissue of the heart to thicken. Once the muscle has thickened, it pretty much is permanent and there is little modern medicine can do to reverse it. They will most likely prescribe beta blockers or antihypertensives in order to relax the muscle some and help it fill a bit more during diastole. Best of luck my friend.