Changes in left ventricular geometry after subannular repair in type IIIb functional mitral regurgitation

OBJECTIVES Papillary muscle repositioning in functional mitral regurgitation (FMR) alleviates mitral valve (MV) tenting by reducing the distance between papillary muscle tips and MV annular plane, i.e. apical left ventricular (LV) displacement. We aimed to quantify the effect of papillary muscle repositioning on papillary muscle geometry and to evaluate whether improved papillary muscle geometry after papillary muscle repositioning translates into the global LV reverse remodelling in FMR type IIIb. METHODS Patients with severe FMR type IIIb were prospectively enrolled and underwent pre- and postoperative 1.5-T cardiac magnetic resonance imaging. A new variable was defined, the papillary muscle to mitral annulus distance, which quantifies the distance between papillary muscle tips and MV annular plane. All parameters were measured by 2 independent investigators. RESULTS A total of 63 patients were enrolled. In all patients, papillary muscle to mitral annulus distance correlated significantly with established markers of LV remodelling and MV tenting severity. In patients who underwent subannular papillary muscle repositioning procedure (surgical cohort, n = 23), preoperative median papillary muscle to mitral annulus distance was 30 mm [interquartile range (IQR): 27-34 mm] and was significantly reduced postoperatively to 25 mm (IQR: 21-27 mm) (P = 0.001). LV end-diastolic diameter was reduced from 66 mm (IQR: 60-71) preoperatively to 58 mm (IQR: 53-67) after the surgery (P = 0.001). CONCLUSIONS MV repair with papillary muscle repositioning results in a papillary muscle to mitral annulus distance reduction and significantly improved MV tenting parameters. Improved papillary muscle geometry after papillary muscle repositioning is associated with a global LV reverse remodelling and may, thereby, improve the prognosis of FMR patients.