ABSTRACT
Coronary flow reserve [CFR] is defined as a maximal [hyperemic] to resting ratio of coronary blood flow. It is a physiologic parameter of coronary circulation and depends on the patency of the epicardial coronary arteries and integrity of the microvascular circulation.CFR measurement has many clinical applications including functional assessment of intermediate stenosis, detection of critical stenosis monitoring of coronary flow in the post angioplasty period, assessment of post infarct blood flow and assessment of coronary graft patency. The aim of this study was to measure CFR in the coronary sinus through the transthoracic echocardiographic approach, in patients who were candidate for coronary artery bypass graft surgery [CABG] before and one month after operation. The present study included 19 patients [mean age=56 +/- 9.1] including 15 males and 4 females, admitted for CABG. All patients had a sinus rhythm, normal wall thickness, normal RV systolic pressure, and tricuspid valvular regurgitation equal or less than grade 2. The antegrade phase of coronary flow in the coronary sinus moving into the right atrium was analyzed in two phases [systolic and diastolic]. Each wave was determined considering the peak velocity and velocity time integral [VTI]. The volumetric blood flow in the coronary sinus calculated at the baseline and then in hyperemic phase was used for determination of CFR both before and after CABG. There was a significant increase in the diameter of the coronary sinus after CABG [9.4 +/- 1.2mm] compared with that of before CABG values [8.6 +/- 1.05mm]. Also there was a trend of increasing the diameter in the hyperemic phase before and after CABG. The absolute increase in mean coronary sinus diameter was 0.5 mm before and 1.5 mm after CABG. Coronary flow reserve [CFR] was significantly higher after surgery, despite a significant increase in systolic velocity ratio [hyperemic/baseline] after CABG. This is also true for systolic velocity time integral [VTI] and diastolic VTI ratios, but there was an insignificant increase in diastolic velocity ratio. Our study in accordance with previous studies, denotes that transthoracic measurement of the coronary flow reserve can be used as a feasible and reproducible method to monitor the changes in cardiac perfusion after revascularization