Cardiac hypertrophy is an increase in the mass of the heart’s muscle due to the enlargement of its cells. This thickening, most often in the main pumping chamber known as the left ventricle, occurs when the heart is forced to work harder over a sustained period, similar to how skeletal muscles grow from weight training.
Physiological vs. Pathological Hypertrophy
The heart’s thickening is not always a sign of disease; it can be a normal adaptation to intense physical activity. This is known as physiological hypertrophy, or “athlete’s heart.” In endurance athletes or weightlifters, the heart muscle enlarges to meet the body’s increased demand for blood and oxygen during prolonged, strenuous exercise. This type of growth is typically symmetrical, and the heart’s function remains normal or is even enhanced.
In contrast, pathological hypertrophy is a maladaptive response to chronic disease-related stress. This form occurs when the heart is forced to pump against abnormally high resistance or manage excessive blood volume. Unlike the organized growth in an athlete’s heart, this pathological thickening can lead to stiffness, reduced elasticity, and impaired function. This stiffness, called diastolic dysfunction, means the ventricle cannot relax properly to fill with blood, which can increase the risk for serious cardiac events.
Unlike the balanced growth in an athlete’s heart, the disease-related form can involve fibrosis—the formation of excess fibrous connective tissue—and cellular disorganization. These changes disrupt the heart’s electrical and mechanical functions. Over time, this can lead to a decline in the heart’s ability to pump effectively and progress toward heart failure.
Causes of Pathological Hypertrophy
Pressure overload, where the heart must work harder to eject blood, is a frequent cause. Chronic high blood pressure (hypertension) is a primary example, as the left ventricle constantly contracts against elevated pressure in the arteries. Similarly, aortic valve stenosis, a condition where the heart’s aortic valve is narrowed, creates a physical obstruction that forces the heart muscle to thicken to overcome the resistance.
Volume overload is another cause, leading to a pattern called eccentric hypertrophy where the heart chamber enlarges to accommodate a larger volume of blood. This is often seen in conditions like valve regurgitation, where a valve does not close properly, allowing blood to leak backward into the chamber. For instance, mitral valve regurgitation causes blood to flow back into the left atrium, increasing the total volume the left ventricle must handle with each beat.
Genetic factors also play a direct role in some cases, independent of pressure or volume stressors. The most well-known of these conditions is hypertrophic cardiomyopathy (HCM). HCM is typically caused by inherited mutations in genes that code for sarcomeres, the contractile proteins of heart muscle cells. This genetic defect leads to abnormal thickening of the heart muscle, often in the wall separating the two lower chambers (the septum), which can obstruct blood flow.
Symptoms and Diagnosis
In its early stages, cardiac hypertrophy may not produce any noticeable symptoms. When they appear, common signs include shortness of breath during physical activity, persistent fatigue, and chest pain (angina). Some individuals may also experience palpitations (a rapid or fluttering heartbeat), dizziness, or fainting spells.
The most definitive diagnostic tool is an echocardiogram. This ultrasound of the heart provides direct visualization of the heart’s chambers, allowing a physician to measure the thickness of the ventricle walls, assess valve function, and evaluate how well the heart is pumping.
An electrocardiogram (ECG or EKG) is another common diagnostic test that records the heart’s electrical activity. While it doesn’t visualize the muscle directly, an ECG can detect electrical patterns that suggest ventricular thickening and strain. For more detailed imaging, a cardiac magnetic resonance imaging (MRI) scan may be used. A chest X-ray might also reveal an enlarged heart silhouette, although it is less specific than an echocardiogram or MRI.
Medical Management and Treatment
Treatment for cardiac hypertrophy is primarily directed at managing the underlying condition that is causing the heart muscle to overwork. Lifestyle modifications are a foundational component of management, especially for hypertrophy caused by high blood pressure. Patients are often advised to adopt a low-sodium diet, engage in regular moderate exercise as approved by their doctor, and cease smoking.
Medications are prescribed to reduce strain on the heart by lowering blood pressure, slowing the heart rate, and allowing it to function more efficiently. Common classes of drugs include beta-blockers and calcium channel blockers, which help relax the heart muscle and reduce its workload. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) are also widely used to lower blood pressure.
For hypertrophy caused by specific structural problems, surgical or procedural interventions may be necessary. If a faulty heart valve is the cause, an operation to repair or replace the valve can resolve the issue. In severe cases of obstructive hypertrophic cardiomyopathy, a surgical procedure called a septal myectomy may be performed to remove a portion of the thickened septal wall. In less invasive procedures like alcohol septal ablation, a small amount of alcohol is injected to shrink the thickened tissue.