Restricted coronary flow reserve in patients with mitral regurgitation improves after mitral reconstructive surgery

Objectives. The purpose of this study was to assess coronary flow characteristics in patients with chronic mitral regurgitation (MR). Background. Coronary flow reserve (CFR) has been reported to be restricted in cases with left ventricular (LV) volume overload caused by aortic regurgitation and increased LV preload. Methods. The study populations consisted of 31 patients with nonrheumatic chronic MR. Eleven with chest pain and normal coronary arteries served as control subjects. Phasic coronary flow velocities were obtained in the proximal segment of the angiographically normal left anterior descending coronary artery at rest and during hyperemi (0.14 mg/kg/min adenosine infusion intravenously) using 0.014-in. (0.036 cm), 15-MHz Doppler guide wire. Coronary flow reserve was obtained from the ratio of hyperemic/baseline time-averaged peak velocity (APV). Thirteen cases who underwent mitral valve reconstructive surgery were also studied 1 month after surgery. Results. Compared with control subjects, CFR was significantly reduced in cases with MR (2.1 ± 0.5 vs. 3.3 ± 0.6, respectively, p < 0.01) because baseline APV was significantly greater (28 ± 8 vs. 19 ± 6 cm/s, respectively, p < 0.01), although maximal hyperemic APV was not significantly different (56 ± 14 vs. 61 ± 16 cm/s, respectively, p = NS). Significant correlations were obtained between CFR and LV end-diastolic pressure (LVEDP) (r = 0.70, p < 0.01), LV mass index (r = 0.42, p < 0.01), LV end-diastolic volume (r = 0.38, p = 0.04) and MR volume (r = 0.39, p = 0.03), and stepwise regression analysis showed LVEDP was the most important determinant of CFR in MR (r2 = 0.49, p < 0.0001). This restricted CFR improved significantly after mitral valve reconstructive surgery (2.1 ± 0.5 vs. 3.1 ± 0.6, respectively, p < 0.01) because of reduction of baseline APV (28 ± 8 vs. 21 ± 8 cm/s, respectively, p < 0.01). Conclusions. Coronary flow reserve is limited in cases with MR because of elevation of baseline resting flow velocity. This reduction of CFR correlates well with increase in LV preload, mass and volume overload, especially with increase in LV preload, and this restricted CFR improves after mitral valve surgery.