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Cardiac Enlargement: A Patient Guide

By Dr. Joseph Toscano

What is cardiac enlargement?

Cardiac enlargement refers to an increase in the size of the heart. There are two types of cardiac enlargement: hypertrophy and dilation. (Though usually occurring separately, they may occur at the same time.) Hypertrophy involves an increase in the thickness of the heart muscle. Dilation involves an increase in the size of the inside cavity of a chamber of the heart. Hypertrophy usually occurs in only one chamber while dilation may occur in one, two, three, or all of the chambers, based on its cause. In most cases, cardiac enlargement is abnormal and accompanied by additional cardiovascular problems. The one exception is regular aerobic exercise, which produces a beneficial enlargement involving both hypertrophy and dilation of the heart.

What causes cardiac hypertrophy?

Hypertrophy, or thickening, of the heart muscle occurs in response to increased stress on the heart. It typically involves one of the bottom chambers of the heart, which are known as the ventricles. The right ventricle pumps blood to the lungs and the left ventricle pumps blood to the body. The most common causes of hypertrophy are related to increased blood pressure in either the lungs or the body. The extra work of pumping blood against the increased pressure causes the ventricle to thicken over time, the same way a body muscle increases in mass in response to weightlifting.

High blood pressure, or hypertension, is the most frequent cause of left ventricular hypertrophy (LVH). Stenosis of the aortic valve – a condition in which, for a variety of reasons, this heart valve cannot open fully – is another common cause of LVH. Hypertrophic cardiomyopathy (a disease previously known as idiopathic hypertrophic subaortic stenosis or IHSS), and the ongoing use of cocaine round out the list of most common causes of LVH. Hypertrophic cardiomyopathy is a genetic disease related to weakness of the individual muscle fibers of the heart. These fibers need to work harder to pump blood and become thickened over time. Hypertrophic cardiomyopathy occurs in 1 in 500 people and is the most common cardiac cause of sudden death in young athletes.

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