Many people with hypertrophic cardiomyopathy do not have symptoms. However, if symptoms develop, initially they generally include:

• Shortness of breath (dyspnea), especially with exercise or exertion.
• Chest pain (angina).
• Fainting or near-fainting (syncope), especially with exertion.
• Heart palpitations, an uncomfortable awareness of the heart beating rapidly or irregularly.

Sudden death may occur from the onset of ventricular tachycardia (a type of rapid heart rate) or other dangerous arrhythmias. A genetic factor appears to influence which people with hypertrophic cardiomyopathy are more prone to sudden death. Other risk factors for sudden death include severe obstruction of the left ventricle, multiple fainting (syncope) episodes, recurring episodes of ventricular tachycardia, and an abnormal drop in blood pressure during exercise.⁴

Although it can occur in any age group, sudden death is most shocking when it happens to young adults or athletes. While these tragic deaths are often given prominence in the media, recent studies show that sudden death is more rare (1% per year) than once believed.⁵

Complications of hypertrophic cardiomyopathy

Atrial fibrillation is a common complication of hypertrophic cardiomyopathy. This abnormal heart rhythm interferes with the normal pumping of the heart. It can cause blood clots to develop in the heart, which can break off and travel through the bloodstream (systemic embolism). This may cause a stroke, heart attack, or blocked blood flow to an arm or leg.

Heart failure may develop if the disease progresses. In heart failure, the heart's lower chambers are not able to pump blood effectively enough to meet the body's needs for oxygen and nutrients. Common symptoms include fluid buildup (edema) in the legs, ankles, and feet; shortness of breath while lying down or exercising; and increased urination at night.

Athlete's heart syndrome

People who exercise regularly and vigorously often develop changes in their heart muscle that can be confused for hypertrophic cardiomyopathy. In such athletes, the heart muscle grows to adapt to the extra demands from physical activities. This condition is called athlete's heart syndrome. But unlike hypertrophic cardiomyopathy, athlete's heart syndrome does not cause life-threatening heart rhythms and sudden death. It is a benign, or harmless, condition. When an athlete stops training, the heart returns to a normal size unlike those with hypertrophic cardiomyopathy, in which the heart remains enlarged.