Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle (myocardium) becomes abnormally thick — or hypertrophied. This thickened heart muscle can make it harder for the heart to pump blood. Hypertrophic cardiomyopathy may also affect the heart’s electrical system.
Hypertrophic cardiomyopathy often goes undiagnosed because many of those with hypertrophic cardiomyopathy have few, if any, symptoms.
In a small number of people with this condition, the thickened heart muscle can cause signs and symptoms, such as shortness of breath and problems in the heart’s electrical system resulting in life-threatening abnormal heart rhythms (arrhythmias).
Cause
Hypertrophic cardiomyopathy is usually caused by gene mutations. It’s thought these mutations cause the heart muscle to grow abnormally thick. People with hypertrophic cardiomyopathy also have an abnormal arrangement of heart muscle fibers. The heart muscle cells become jumbled, known as myofiber disarray. This disarray can contribute to an irregular heartbeat (arrhythmia) in some people.
Hypertrophic cardiomyopathy is usually inherited. There’s a 50 percent chance that the children of those with hypertrophic cardiomyopathy will inherit the genetic mutation for the disorder. Siblings of those with hypertrophic cardiomyopathy also are at risk. As a result, close relatives of someone with hypertrophic cardiomyopathy are urged to talk to their doctors about getting screened for the disease.
Hypertrophic cardiomyopathy occurs in about one in every 500 people and affects men and women equally.
Types
The severity of hypertrophic cardiomyopathy varies widely. Most people with hypertrophic cardiomyopathy have a form of the disease in which the wall (septum) between the two bottom chambers of the heart (the ventricles) becomes enlarged and obstructs blood flow. This is sometimes referred to as hypertrophic cardiomyopathy with obstruction or hypertrophic obstructive cardiomyopathy. About 70 percent of those with hypertrophic cardiomyopathy have some form of obstruction.
Sometimes hypertrophic cardiomyopathy occurs without significant obstruction of blood flow. However, the heart’s main pumping chamber (the left ventricle) may become stiff, which reduces how much blood the ventricle can hold and how much blood gets pumped out to the body with each contraction. Doctors sometimes refer to this as hypertrophic cardiomyopathy without obstruction or nonobstructive hypertrophic cardiomyopathy.
Risk & complications
In many people, hypertrophic cardiomyopathy does not cause significant health problems. However, in some people, hypertrophic cardiomyopathy can cause severe signs and symptoms, such as shortness of breath, chest pain or fainting.
People with hypertrophic cardiomyopathy are at risk of dangerous abnormal heart rhythms (arrhythmias), such as ventricular tachycardia or ventricular fibrillation. These abnormal heart rhythms can cause sudden cardiac death.
Hypertrophic cardiomyopathy is the leading cause of heart-related sudden death in people under 30. Fortunately, such deaths are rare.
Possible complications of hypertrophic cardiomyopathy include:
Arrhythmias – Thickened heart muscle, as well as the abnormal structure of heart cells (disarray), can disrupt the normal functioning of the heart’s electrical system, resulting in fast or irregular heartbeats. Atrial fibrillation, ventricular tachycardia and ventricular fibrillation are among the arrhythmias that may be caused by hypertrophic cardiomyopathy.
The most dreaded complication of hypertrophic cardiomyopathy is sudden cardiac death due to ventricular tachycardia or ventricular fibrillation. Unfortunately, it can be difficult to predict which people with hypertrophic cardiomyopathy are most prone to these life-threatening, abnormal heart rhythms. If you experience fainting spells, extreme dizziness or prolonged palpitations, you should seek immediate medical care.
Obstructed blood flow – In many people, the thickened heart muscle causes obstruction to blood flow leaving the heart. This can lead to shortness of breath with exertion, chest pain, dizziness and fainting spells.
Mitral valve problems – The thickened heart muscle can leave a smaller space for blood to flow, which in turn causes blood to rush through your heart valves more quickly and more forcefully. This increased force can prevent your mitral valve — the valve between your heart’s left atrium and left ventricle — from closing properly. As a result, blood can leak backward into the left atrium. This is called mitral valve regurgitation. Mitral valve regurgitation can lead to other complications, such as heart failure or arrhythmias.
Heart failure – Heart failure means your heart can’t pump enough blood to meet your body’s needs. The thickened heart muscle of hypertrophic cardiomyopathy can eventually become too stiff to fill effectively and can lead to shortness of breath and heart failure.
Dilated cardiomyopathy – Over time, thickened heart muscle may become weak and ineffective and the ventricle becomes enlarged (dilated) and its pumping ability becomes less forceful.
Treatment
The goals of treatment for hypertrophic cardiomyopathy are to relieve symptoms and prevent sudden cardiac death in those at high risk.
Treatment options for hypertrophic cardiomyopathy include drugs, surgery or other methods to destroy obstructive heart tissue or implantation of devices to help control heart rhythm, such as:
Drug treatment – This is the best option for most people. Various medications can help relax the muscle and slow the rate so that the heart can pump more efficiently. Some of the drugs your doctor may suggest include beta blockers, calcium channel blockers or the anti-arrhythmic medications disopyramide or amiodarone.
Septal myectomy – This is an open-heart operation in which the surgeon removes part of the thickened, overgrown heart muscle wall (septum) that separates the two bottom heart chambers (ventricles). Removing part of this overgrown muscle improves blood flow and reduces mitral regurgitation. Myectomy is used if medications don’t relieve symptoms. Most people who have symptoms and undergo myectomy have no further symptoms. This type of surgery is only available in medical centers that specialize in the treatment of hypertrophic cardiomyopathy.
Septal ablation – Also called septal alcohol ablation, this is a new treatment in which a small portion of the thickened heart muscle is destroyed by injecting alcohol through a catheter into the artery supplying blood to it. There are possible complications with this procedure, including heart block — a disruption of the heart’s electrical system — which requires implantation of a pacemaker. The long-term success of this procedure isn’t yet known, but it’s becoming more commonly used.
Pacemaker implantation – A pacemaker is a small electronic device inserted under your skin that sends electrical signals to your heart to monitor and regulate your heartbeat. Surgery to implant the pacemaker is usually performed under local anesthesia and typically takes less than three hours. Pacemaker implantation is generally not as effective as surgical options, but it’s sometimes used in older people who want to avoid more invasive procedures.
Implantable cardioverter-defibrillator (ICD) – This is a pager-sized device implanted in your chest like a pacemaker. An ICD continuously monitors your heartbeat. If a life-threatening arrhythmia occurs, the ICD delivers precisely calibrated electrical shocks to restore a normal heart rhythm. A small number of people with hypertrophic cardiomyopathy are at risk of sudden cardiac death because of abnormal heart rhythms. In these high-risk individuals, many doctors recommend the implantation of an ICD.
Source: Mayo Clinic