The heart is composed of 4 chambers: left and right atria, and left and right ventricles. These are composed of muscle. Like any other muscle in the body, when the heart is forced to work, it grows bigger and thicker. When the left ventricle, which pumps blood to the whole body, pumps against high pressures (for example, high blood pressure) for years, it will grow thickened. While a big and thick heart sounds like a good thing, it eventually works against the heart. After the heart has reached a certain point of thickness, it will no longer be able to relax. Relaxing is important because that is when the heart fills with blood. If the heart does not fill with enough blood, then it cannot pump enough blood. This condition is sometimes known as diastolic heart failure (or ejection fraction preserved heart failure).

Left ventricular hypertrophy, or LVH, can be reversed to some extent by eliminating the cause of the problem. If blood pressure has caused LVH, then controlling the blood pressure is the most important aspect of treatment. Frequently people require multiple blood pressure agents to get the best control.