Background: Measuring the coronary flow velocity reserve (CFVR) by transthoracic Doppler echocardiography (TTDE) has been widely performed using adenosine. Although adenosine infusion is known to induce transient variation of hyperemia, the timing to measure the CFVR has not been well addressed. Therefore, we aimed to clarify the difference between the peak CFVR and at 2 min following adenosine triphosphate (ATP) infusion compared to the CFVR after low-dose dipyridamole infusion.
Methods and results: A total of 26 patients with coronary artery diseases underwent TTDE. The coronary flow velocity (CFV) of the left anterior descending artery (LAD) was monitored during ATP infusion at 0.14 mg/kg/min. The CFVR was measured both at the first peak and at 2 min following ATP infusion, and after dipyridamole infusion at 0.56 mg/kg/min for 4 min. The first peak of hyperemia occurred 63.7 ± 8 s after starting ATP infusion. The value of the peak CFVR was significantly higher than the CFVR at 2 min following ATP stress, which was equivalent to the CFVR after dipyridamole infusion (2.30 ± 0.92, 1.83 ± 0.77, and 1.70 ± 0.68, respectively, P < 0.001). Applying a cut-off value of 2.0 to predict angiographic LAD stenosis, the CFVR at 2 min following ATP stress was significantly correlated to the angiographic findings. However, the peak CFVR after ATP infusion did not correlate with the angiographic findings.
Conclusions: During ATP infusion, the peak CFVR was significantly higher than the CFVR at 2 min, which was equivalent to the CFVR after low-dose dipyridamole. This finding should be considered for the standardization of CFVR measurements.
Keywords: Adenosine; Coronary flow velocity; Dipyridamole; Transthoracic Doppler echocardiography.