In patients with HCM, the carotid pulse has an initial brisk rise, followed by a decline, then a second rise. In aortic stenosis, the carotid upstroke is slowed and the amplitude low (pulsus parvus et tardus).
Which noninvasive laboratory evaluations are helpful in evaluating patients with suspected HCM?
Useful noninvasive laboratory tests include electrocardiography (ECG), chest x-ray, and echocardiography. The ECG may be normal but is usually abnormal in symptomatic patients, showing nonspecific ST and T-wave changes, LV hypertrophy, deep broad Q waves in the inferolateral leads, left axis deviation, and left atrial enlargement. Arrhythmias (supraventricular and ventricular) may be present on ambulatory monitoring.
The chest x-ray may be normal but usually shows mild to moderate increase in the cardiac silhouette.
Echocardiography is the cornerstone of the diagnosis of HCM. Ventricular hypertrophy is the cardinal feature seen on the echocardiogram. The septum is usually 15 mm thick with a septal-to-posterior wall ratio of 1.3-1.5. Other features include narrowing of the LV outflow tract formed by the interventricular septum anteriorly and the anterior mitral valve leaflet posteriorly (accentuated further with the Valsalva maneuver or amyl nitrite), a small LV cavity, and partial systolic closure or fluttering of the aortic valve. Color flow Doppler imaging may reveal mitral regurgitation.