Background: This study assessed the feasibility of transthoracic Doppler scan echocardiography (TTDE) combined with echo-contrast agent in measuring coronary flow velocity (CFV) and coronary flow velocity reserve (CFVR) in the left anterior descending artery.
Methods: In 68 consecutive patients who underwent cardiac angiography, TTDE was recorded before and after induction of a hyperemic condition with intravenous administration of adenosine triphosphate (0.14 mg/kg/min). After CFV values returned to baseline, the same measurements were repeated while an echo-contrast agent was continuously infused. CFVR was assessed as the ratio of hyperemic to basal CFV. The pulsed wave Doppler scan quality was graded from 1 to 3 (TTDE score: 1, no signal detection; 2, poor definition of outline; 3, optimal outline definition).
Results: Before enhancement, CFVR could not be measured in 20 patients. Prevalence of delayed stenosis (Thrombolysis In Myocardial Infarction [TIMI] II grade flow) in these patients (30%) was significantly greater than in those whose CFVRs could be measured without enhancement (2%; P <.01). TTDE scores both at baseline and after hyperemia were significantly improved with contrast enhancement (before, 2.8 +/- 0.6; after, 3.0 +/- 0.3; P <.01; before, 2.6 +/- 0.7; after, 3.0 +/- 0.3; P <.01; respectively). Overall contrast enhancement increased the rate of successful CFVR measurement from 70% to 97% (P <.01). Sensitivity and specificity of significant left anterior descending artery stenosis detection with CFVR of <2.0 were 94.4% and 87.8%, respectively.
Conclusion: These data suggest that administration of echo-contrast agent improves pulse wave Doppler scan quality and thus the feasibility of measuring CFVR.