Noninvasive quantification of coronary blood flow reserve in humans using myocardial contrast echocardiography.

BACKGROUND We hypothesized that coronary blood flow (CBF) reserve could be quantified noninvasively in humans using myocardial contrast echocardiography (MCE). METHODS AND RESULTS Eleven patients with normal epicardial coronary arteries (group I) and 19 with single-vessel coronary stenosis (group II) underwent quantitative coronary angiography, MCE, and CBF velocity measurements at rest and during intravenous adenosine infusion. In group I patients, MCE-derived myocardial blood flow (MBF) velocity reserve (2.4+/-0.08) was similar to CBF velocity reserve using a Doppler flow wire (2.4+/-1.1). Patients with a single risk factor had a significantly higher MBF reserve (3.0+/-0.89) than those with >/=2 risk factors (1.7+/-0.22). In group II patients, significant differences were found in MBF velocity reserve in patients with mild (<50%), moderate (50% to 75%), or severe (>75%) stenoses (2.2+/-0.40, 1.6+/-0.65, and 0.55+/-0.19, respectively; P=0.005). A linear relation was found between flow velocity reserve determined using the 2 methods (r=0.76, P<0.001), and a curvilinear relation was noted between the percent coronary stenosis measured using quantitative coronary angiography and velocity reserve using both methods. CONCLUSIONS CBF reserve can be measured in humans using MCE. This method may allow the noninvasive assessment of coronary stenosis severity and the detection of microvascular dysfunction.