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 151Ϯ52 to 131Ϯ53 mL/m 2 (Pϭ0.0001) and from 114Ϯ48 to 92Ϯ50 mL/m 2 (Pϭ0.0001), respectively. Global ESS decreased from 157Ϯ43 to 139Ϯ50 kdyne/cm 2 (Pϭ0.01), and LV ejection fraction improved from 27Ϯ8.0 to 33Ϯ13% (Pϭ0.0007). There were significant correlations between change in LVEDVI and LVESVI (rϭ0.88, PϽ0.0001) and change in LVESVI and global ESS (rϭ0.68, Pϭ0.0002). Moreover, the magnitude of increase in LV ejection fraction significantly correlated with the degree of reduction in global ESS (rϭϪ0.61, Pϭ0.002). 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.

Serial multidetector computed tomography assessment of left ventricular reverse remodeling, mass, and regional wall stress after restrictive mitral annuloplasty in dilated cardiomyopathy

“…Since then, short-term and midterm survival rates and the extent of ventricular reverse remodeling (decrease in LV volume) after MR correction have been reported. 2,3 However, follow-up data on ventricular reverse remodeling after RMA in patients with end-stage cardiomyopathy are scarce. Moreover, the existing follow-up studies used echocardiography, which is not optimal for a precise assessment.…”

“…We recently developed MDCT-based analysis software to compute local circumferential myocardial stress. [3][4][5] The objective of the present study was to assess the serial changes in the LV volumes, function, and mass and in regional myocardial stress before, and early and late after…”

“…The mechanism and process of the reverse remodeling have not been fully evaluated. 3 The present study focused on the serial changes in a detailed fashion on various aspects of the reverse remodeling process, such as the LV volume, LV functional performance, regional wall stress, and LV mass, as measured using MDCT images, in patients with functional MR associated with DCM who underwent RMA. We must note that in previous reports LV reverse remodeling (eg, LV volumes and mass) was noted in early (2 months) and was present in long (3-4 years) follow-up after RMA in the patients with DCM.…”

“…The imaging analysis used to assess regional myocardial stress was performed on a personal computer with dedicated analysis software (Osaka University-OSCAR STRESS tool, Osaka, Japan), as described previously. [3][4][5] The regional end-systolic stress (ESS) was computed at 16 segments (ie, excluding the apical cap; segment no. 17).…”

Mitral Loop Cerclage Annuloplasty for Secondary Mitral Regurgitation

“…In experimental animals with ischemic mitral regurgitation, undersized Paneth mitral annuloplasty sufficient to abolish mitral regurgitation led to reduced global and regional LV dimensions and modestly increased end-systolic elastance (16). In patients undergoing undersized surgical mitral annuloplasty for secondary mitral regurgitation, both pre-operative and post-operative global end-systolic myocardial wall stress predicted clinical improvement, suggesting that reduced end-systolic stress achieved by annuloplasty may contribute to reverse remodeling (17), and may interrupt the vicious cycle of mitral regurgitation and progressive ventricular dysfunction. Remarkably, there was also a suggestion in our experience of electrical remodeling (reversion of atrial fibrillation to sinus rhythm in 2 subjects), as a possible functional correlate of the geometric remodeling (18).…”