Does down-sized ring annuloplasty induce papillary muscle relocation in ischemic mitral regurgitation?

BACKGROUND AND AIM OF THE STUDY

Down-sized ring annuloplasty has been shown to induce left ventricular remodeling in patients with functional ischemic mitral regurgitation (FIMR). To determine if this remodeling comprised papillary muscle (PM) relocation, a chronic FIMR porcine model was used to assess the impact on three-dimensional (3D) PM positioning, by implanting a down-sized rigid ring annuloplasty.

METHODS

Six out of ten FIMR pigs that underwent a down-sized mitral ring annuloplasty (CE Classic size 26-28) survived for six weeks postoperatively. 3D cardiac magnetic resonance imaging was carried out at one week preoperatively, and repeated at one and six weeks postoperatively, to assess the direct distances (in mm) from the anterior papillary muscle (APM) and posterior papillary muscle (PPM) to each trigone. Three reference planes were also constructed to determine APM and PPM displacement in the lateral, anterioposterior, and apical directions.

RESULTS

Relative to the preoperative situation, at one week postoperatively a reduced displacement of the APM was observed in an anterior direction (from 18.8 to 16.2 mm; p < 0.05) and from the posterior trigone (from 40.5 to 37.4 mm; p < 0.05) at end-diastole. Relative to one week postoperatively, at six weeks postoperatively a reduced PPM displacement was observed from the anterior trigone (43.0 versus 42.0 mm; p < 0.05) at end-systole. Relative to the preoperative situation, no overall tendency of surgically induced PM relocation was observed at one or six weeks postoperatively.

CONCLUSION

A down-sized ring annuloplasty did not induce an overall pattern of PM relocation in pigs with chronic FIMR.