Complications

Many people with hypertrophic cardiomyopathy (HCM) don't have significant health problems. But complications of hypertrophic cardiomyopathy can include:

• Atrial fibrillation. Thickened heart muscle, as well as the abnormal structure of heart cells, can cause changes in the heart's electrical system, resulting in fast or irregular heartbeats. Atrial fibrillation can also increase your risk of developing blood clots, which can travel to your brain and cause a stroke.
• Blocked blood flow. In many people, the thickened heart muscle blocks the blood flow leaving the heart, causing shortness of breath with exertion, chest pain, dizziness and fainting spells.
• Mitral valve problems. If the thickened heart muscle blocks the blood flow leaving the heart, the valve between the left atrium and left ventricle (mitral valve) may not close properly. As a result, blood can leak backward into the left atrium (mitral valve regurgitation), possibly leading to worsening symptoms.
• Dilated cardiomyopathy. In a very small number of people with HCM, the thickened heart muscle may become weak and ineffective. The ventricle becomes enlarged (dilated), and its pumping ability becomes less forceful.
• Heart failure. The thickened heart muscle can eventually become too stiff to effectively fill the heart with blood. As a result, your heart can't pump enough blood to meet your body's needs.
• Sudden cardiac death. Rarely, hypertrophic cardiomyopathy can cause heart-related sudden death in people of all ages. Because many people with hypertrophic cardiomyopathy don't realize they have it, sudden cardiac death may be the first sign of a problem. It can happen in seemingly healthy young people, including high school athletes and other young, active adults.