Clinical application of transthoracic Doppler echocardiography to assess coronary flow reserve.

This review discusses methods (focusing on noninvasive transthoracic Doppler echocardiography) to measure coronary endothelium-independent and endothelium-dependent vasodilatation. Coronary flow reserve is an important functional parameter to understand the pathophysiology of coronary circulation. Coronary flow reserve measurement is used to assess epicardial coronary stenoses or to examine the integrity of microvascular circulation. In the presence of coronary artery stenosis, coronary flow reserve is an important hemodynamic parameter for clinical decision making (for example to refer or defer patients with intermediate stenosis [40-70%] to PTCA). In the absence of stenosis in the epicardial coronary artery, the coronary flow reserve may be decreased when coronary microvascular circulation is impaired by arterial hypertension with or without left ventricular hypertrophy, diabetes mellitus, hypercholesterolemia, hypertrophic cardiomyopathy, aortic stenosis or syndrome X.