Hypertrophic cardiomyopathy (HCM) can occur at any age, characterized by thickening of the ventricular myocardium, particularly the interventricular septum, leading to a reduced ventricular cavity. A systolic pressure gradient between the left ventricle and the aorta is often present. Approximately one-third of cases have a family history, and it is considered an autosomal dominant genetic disorder.

bubble_chart Diagnosis

Due to differences in age, degree, and location of myocardial hypertrophy, the clinical features and conditions of children vary greatly. Although the disease can occur during the neonatal period, it mostly affects school-aged children.

(1) Symptoms Early symptoms include dyspnea after exercise, gradually progressing to lack of strength, dizziness, or syncope. Precordial pain may also occur, while heart failure typically appears in the advanced stage.

(2) Signs The cardiac border expands to the left, and an intermediate stage [second stage] or advanced stage systolic murmur may be heard at the lower left sternal border, sometimes accompanied by tremor, the latter being seen in cases with outflow tract obstruction.

(3) Electrocardiogram Abnormalities are common. Infants and young children often exhibit right ventricular hypertrophy, which is actually the result of abnormal depolarization of the hypertrophied interventricular septum. Older children more commonly show left ventricular hypertrophy and strain, or even abnormal Q waves.

(4) X-ray Examination Although varying degrees of cardiac enlargement are present, there is a lack of specific morphological changes in the heart.

(5) Echocardiography Two-dimensional echocardiography is currently a crucial diagnostic tool. A ratio of the interventricular septum (IVS) to the left ventricular posterior wall (LVPW) greater than 1.5 (i.e., IVS/LVPW ≧1.5) is widely adopted as a diagnostic criterion for this condition. Combined with M-mode mitral valve curves and Doppler spectral analysis, it can also determine whether left ventricular outflow tract obstruction is present.

﹝Treatment﹞

(1) According to the condition, appropriately limit activity or even enforce bed rest. (2) Drugs that enhance myocardial contractility, such as Digitalis-like agents and isoproterenol, may aggravate left ventricular outflow tract obstruction and should be avoided as much as possible. (3) β-adrenergic blockers can reduce myocardial contraction, alleviate outflow tract obstruction, decrease myocardial oxygen consumption, enhance ventricular diastolic expansion, and also slow the heart rate while increasing stroke volume. Propranolol is commonly used at 1–2 mg/kg per day, with the dose gradually increased after initiation to improve symptoms without causing excessively low heart rate or blood pressure. However, recent studies have found that this drug does not reduce arrhythmias nor affect prognosis. (4) Calcium antagonists have both negative inotropic effects to weaken myocardial contraction and improve myocardial compliance, benefiting diastolic function. Verapamil can be used at 2 mg/kg per dose, 3–4 times daily, or diltiazem can be started at 0.5 mg/kg per dose, 3 times daily, gradually increasing to 1 mg/kg per dose. The combination of β-blockers and calcium antagonists may yield better results than either alone. (5) For patients with severe angina or syncope episodes unresponsive to drug therapy, or those with severe left ventricular outflow tract obstruction, surgical resection of hypertrophic myocardial tissue may be performed to relieve symptoms.