There is tremendous variation in the presentation and course of hypertrophic cardiomyopathy (HCM). While some patients have no or mild symptoms, others may have more serious symptoms. About 10 percent of patients with hypertrophic cardiomyopathy develop abnormal heart rhythms (arrhythmias), which increase the risk of sudden cardiac arrest.
The more severe cases usually appear at birth or in infancy with signs of congestive heart failure. Older children with HCM may not have obvious symptoms and therefore be unaware that they have the disease. Symptoms usually emerge as the child approaches the rapid growth period of late childhood and early adolescence. For these children, symptoms can start to appear or become more pronounced during strenuous exercise or participation in competitive sports.
The severity of symptoms is related to the extent and location of the hypertrophy and whether there is obstruction to blood leaving the heart or valve leakage between the heart chambers. Generally children with non-obstructive HCM have milder symptoms than those with obstructive HCM. The first sign of HCM may be a heart murmur in obstructive cases.
Common HCM symptoms may include:
Infants may also exhibit:
In advanced HCM, the heart muscle stretches to compensate for poor pumping and the heart chambers enlarges to eventually resemble dilated cardiomyopathy. Children may then experience symptoms of heart failure, such as coughing, vomiting, abdominal pain, fatigue and weakness, and swelling of legs, feet and abdomen.