Left ventricular hypertrophy (LVH) is the result an underlying condition that causes the heart muscle of the left ventricle to grow and thicken. There are two main causes for LVH, which include:

• Systolic overload. In most cases of LVH, the left ventricle is being strained during the systole, the phase of the heartbeat in which the heart contracts to pump blood. Systolic overload tends to result in thickening but very little enlargement of the left ventricle, which is known as predominant LVH. Thickening of the heart muscle is considered a compensatory mechanism in response to excessive work. When this mechanism fails, heart enlargement (dilation) with subsequent heart failure may result. The most common cause of systolic overload is hypertension. Other causes include aortic valve stenosis and congenital anomalies such as coarctation of the aorta.
  
  
• Diastolic overload. Diastolic overload is a strain on the left ventricle resulting from conditions that overload it with blood during diastole. This is the phase of the heartbeat in which the heart relaxes and takes in oxygen-rich blood, ready for the next contraction. In diastolic overload, the thickening can eventually be associated with progressive enlargement (dilatation) of the left ventricular chamber as it stretched to accommodate the extra blood. Causes of diastolic overload include mitral and aortic valve regurgitation and dilated cardiomyopathy.

An inherited condition, called hypertrophic cardiomyopathy, results in a thickening of both the left and the right ventricles. The condition is due to genetic defects in the enzymes that regulate heart muscle growth and/or metabolism. It may lead to sudden death, heart failure and arrhythmias.

In rare cases, well-trained athletes may experience physiologic hypertrophy. These individuals do not exhibit hypertension or signs of heart failure. It is important to differentiate this condition from other serious conditions that may not show symptoms, such as aortic stenosis or hypertrophic cardiomyopathy. Physiologic hypertrophy usually goes away after a period of physical training is discontinued.

Risk factors for LVH include:

• Age. Most of the conditions that cause LVH (e.g., hypertension, valvular disease) increase with age.
  
  
• Obesity. The larger the body, the harder the heart has to work to pump blood around it. This can lead to LVH. Additionally, obesity increases the risk of other conditions that cause LVH.
  
  
• Coronary disease. Blockages in the blood vessels that restrict the flow of blood increase the workload of the heart.
  
  
• Race. Recent studies have shown a grater prevalence of LVH among black Americans. This may be related to the higher instance of hypertension in this population.