Effects of Targeted Papillary Muscle Relocation on Mitral Leaflet Tenting and Coaptation

Abstract

Ischemic mitral valve (MV) repair for patients with severe left ventricular dilation remains challenging. The objective of this study was to investigate the efficacy of papillary muscle (PM) relocation to restore physiologic MV function. Fresh ovine MVs (n = 6) were studied in a left-heart simulator under physiologic hemodynamics. Ischemic MV disease was simulated by annular dilation and PM displacement. Initial valvular repair was performed with mitral annuloplasty; further PM displacement simulated progressive left ventricular dilation. Basal PM repositioning (Kron procedure), performed to alleviate leaflet tethering, consisted of relocating (1) both PMs toward the commissures; (2) both PMs toward the trigones; (3) the posteromedial PM toward the ipsilateral commissure; and (4) the posteromedial PM toward the ipsilateral trigone. Coaptation length and tenting area were measured using three-dimensional echocardiography as surrogates of MV function. Papillary muscle relocation as an adjunct to mitral annuloplasty statistically improved coaptation length and tenting area compared with the disease condition. No statistical differences in coaptation length and tenting area were observed between final repaired conditions and control conditions. No statistical differences were observed between commissural and trigonal repairs at any incremental repair step. Coaptation length and tenting area were plotted against PM distance; the data were fit to linear regressions. In a realistic in vitro model of ischemic left ventricular dilation, apical-basal PM relocation, as an adjunct procedure to mitral annuloplasty, restored optimal MV closure. Trigonal or commissural traction suture location did not significantly affect the degree of restored coaptation. Linear relationships between PM positions and leaflet variables were established, which could be used to inform surgical repairs.