What can cause the heart to enlarge and weaken?

Here you go:

Chronic disease of the heart muscle

High blood pressure- A chronic medical condition in which the blood pressure is elevated. it is also referred to as high blood pressure or shortened to ht, htn or hpn. the Word "hypertension", by itself, normally refers to systemic, arterial hypertension.

Cardiomegaly- Abnormal enlargement of the heart

Hypertrophic cardiomyopathy- A disease of the myocardium in which a portion of the myocardium is hypertrophied without any obvious cause. it is perhaps most famous as a leading cause of sudden cardiac death in young athletes.

Heart valve disease- Any disease process involving one or more of the valves of the heart. valve problems may be congenital or acquired.