Hypertrophic cardiomyopathy

Alternative names:

cardiomyopathy - hypertrophic; hypertensive hypertrophic cardiomyopathy; idiopathic hypertrophic subaortic stenosis; IHSS

Definition:

A form of cardiomyopathy (heart disease) involving enlargement of the heart muscle, which is out of proportion to any workload on the heart, with the enlargement interfering with the functioning of the heart.

Causes, incidence, and risk factors:

The heart enlargement of hypertrophic cardiomyopathy characteristically is asymmetrical, affecting only one side of the heart. It may interfere with the functioning of the heart by narrowing the outflow of the ventricle and the size of the ventricular chamber, and by reducing the ability of the valves to function properly. The enlargement may directly obstruct the flow of blood.

The obstruction is worsened by situations which increase contraction of the heart (examples include stress, stimulation of the sympathetic nervous system, or medications such as digoxin) or situations which decrease return of blood to the heart (for example, dehydration or excessive use of diuretics).

Two forms of the disease occur:

• 1. IHSS (idiopathic hypertrophic subaortic stenosis): an idiopathic (no known cause) early form of the disease that occurs before the age of 40 and may occur before the age of 10; usually inherited with autosomal dominant transmission. The incidence is about 1 out of 10,000 people.
• 2. An acquired form that occurs in elderly people with a history of high blood pressure (hypertensive hypertrophic cardiomyopathy).