Mechanism of Beneficial Effects of Restrictive Mitral Annuloplasty in Patients With Dilated Cardiomyopathy and Functional Mitral Regurgitation

Abstract

Background— Restrictive mitral annuloplasty (RMA) often leads to reverse left ventricular (LV) remodeling in patients with advanced cardiomyopathy and functional mitral regurgitation. However, the mechanism responsible for its favorable effects on LV ejection performance has been poorly understood. We evaluated systolic wall stress using cineangiographic multidetector computed tomography (MDCT) and our developed software system to assess stress-shortening relations before and after RMA. Methods and Results— Twenty-four patients with dilated cardiomyopathy underwent 64-row MDCT before and 2 months after RMA. All patients underwent stringent downsizing annuloplasty with a semirigid complete ring. Reconstructed images were used to calculate LV end-diastolic index (EDVI) and end-systolic volume index (ESVI), LV ejection fraction, and regional and global end-systolic wall stress (ESS). After RMA, LVEDVI and LVESVI decreased from 151±52 to 131±53 mL/m 2 ( P =0.0001) and from 114±48 to 92±50 mL/m 2 ( P =0.0001), respectively. Global ESS decreased from 157±43 to 139±50 kdyne/cm 2 ( P =0.01), and LV ejection fraction improved from 27±8.0 to 33±13% ( P =0.0007). There were significant correlations between change in LVEDVI and LVESVI ( r =0.88, P <0.0001) and change in LVESVI and global ESS ( r =0.68, P =0.0002). Moreover, the magnitude of increase in LV ejection fraction significantly correlated with the degree of reduction in global ESS ( r =−0.61, P =0.002). Patients without significant reverse LV remodeling had significantly higher preoperative and postoperative global ESS than those with it. Conclusions— Our study suggests that decrease in afterload after reduction in volume overload was responsible for postoperative reverse LV remodeling process after RMA.