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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.
The most
common causes of right ventricle hypertrophy (RVH) are diseases that damage the
lung like emphysema and cystic fibrosis. These diseases destroy blood vessels in
the lung, causing increased pressure in the remaining vessels. Conditions that
decrease oxygen levels, such as chronic bronchitis and sleep apnea, also lead to
RVH. Stenosis of the pulmonic heart valve, repeated blood clots to the lungs
(chronic pulmonary embolism), and primary pulmonary hypertension are a few of
the remaining causes of RVH.
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