Reverse Ventricular Remodeling Reduces Ischemic Mitral Regurgitation

Abstract

Background— In ischemic mitral regurgitation (MR), mitral leaflet closure is restricted by ventricular remodeling with displacement of the papillary muscles (PMs). Therapy is uncertain because ring annuloplasty does not alleviate PM displacement. We tested the hypothesis that echo-guided PM repositioning using an external device can reduce MR without compromising left ventricular (LV) function. Methods and Results— We studied 10 sheep with ischemic MR produced by circumflex ligation with inferior infarction, 6 acutely and 4 eight weeks after myocardial infarction (MI). A Dacron patch containing an inflatable balloon was placed over the PMs and adjusted under echo guidance to reverse LV remodeling and reposition the infarcted PM. 3D echo assessed mitral valve geometric changes. In 7 sheep, sonomicrometry and Millar catheters assessed changes in end-systolic and end-diastolic pressure-volume relationships, and microspheres were injected to assess coronary flow. Moderate MR after MI resolved with patch application alone (n=3) or echo-guided balloon inflation, which repositioned the infarcted PM, decreasing the PM tethering distance from 31.1±2.5 mm after MI to 26.8±1.8 with patch ( P <0.01; baseline=25.5±1.5). LV contractility was unchanged (end-systolic slope=3.4±1.6 mm Hg/mL with patch versus 2.8±1.6 after MI). Although there was a nonsignificant trend for a mild increase in stiffness constant (0.07±0.05 mL −1 versus 0.05±0.03 after MI, P =0.06), LV end-diastolic pressure was unchanged as MR resolved. Coronary flow to noninfarcted regions was not reduced. Conclusions— An external device that repositions the PMs can reduce ischemic MR without compromising LV function. This relatively simple technique can be applied under echo guidance in the beating heart.