Myocardial Ischemia on Thallium Scintigraphy in Hypertrophic Cardiomyopathy
Predictor of Sudden Cardiac Death
An 18-year-old man with known hypertrophic obstructive cardiomyopathy since age 9 was referred for evaluation. His mother had died suddenly at age 24, and her autopsy demonstrated hypertrophic obstructive cardiomyopathy. The patient was asymptomatic. His only medication was propranolol. Two-dimensional echocardiographic images demonstrated normal left ventricular size with hyperdynamic function (ejection fraction 80%) with a septal thickness of 30 mm (Figure, a). The Doppler-derived maximal instantaneous gradient was 21 mm Hg.
An exercise thallium study demonstrated markedly increased thickness of the ventricular septum and part of the anterior wall, with a large area of anterior wall and septal ischemia primarily involving the subendocardium (Figure, b).
Inducible ischemia on thallium scintigraphy identifies a subgroup of young, asymptomatic patients with hypertrophic obstructive cardiomyopathy who are at increased risk of sudden cardiac death. In these patients, more aggressive therapy, including placement of an automatic implantable cardioverter defibrillator, may be warranted.