Noninvasive assessment of intramyocardial coronary flow in hypertrophic cardiomyopathy by high-resolution Doppler echocardiography

Dyspnea and angina have been described in patients with hypertrophic cardiomyopathy (HCM). Given the complexity of the coronary microcirculation, the pathophysiological mechanisms of angina are discussed. The last generation of echo devices allows the investigation of epicardial coronary flow by means of the standard transthoracic approach (TTE). In the present study we describe 5 patients affected by HCM (with outflow tract dynamic obstruction in 2 cases, intraventricular dynamic obstruction in the other 2, no obstruction in the last one) in whom both the epicardial and intramyocardial coronary flows were assessed at high-resolution TTE. Regular flow velocities were shown in epicardial coronary arteries, while in intramyocardial branches the diastolic peak velocity was > 75 cm/s in all patients. Besides, the systolic flow was found to be inverted. Similar to what suggested by the few data presently available in the literature, the main findings of this study confirm the appropriateness of investigating the intramyocardial coronary circulation in patients with HCM by means of high-resolution Doppler echocardiography. In order to explain this clinical finding, an interesting hypothesis of a diastolic "milking-like" phenomenon associated with systolic "blood squeezing" in the intramural coronary arteries was taken into consideration. The noninvasive study of the intramyocardial coronary flow may be clinically relevant even in the evaluation of the effectiveness of the adopted therapeutic strategy in reducing myocardial wall stress in severe ventricular hypertrophy.