Effect of papillary muscle approximation on acute ovine functional tricuspid regurgitation

OBJECTIVES: Ring annuloplasty represents the standard surgical treatment, but offers suboptimal results in patients with severe functional tricuspid regurgitation. Addition of papillary muscles (PMs) approximation may improve clinical outcomes. METHODS: Eight healthy adult male sheep (56 ± 4 kg) underwent cardiopulmonary bypass and implantation of sonomicrometry crystals on the tricuspid annulus, PM tips and right ventricular (RV) free wall. Papillary muscles approximation sutures were anchored between anterior–posterior and anterior–septal PMs and their loose ends externalized through RV free wall to epicardial tourniquets. After weaning from cardiopulmonary bypass, acute right heart failure and tricuspid regurgitation were induced, and subsequent sequential anterior–posterior and anterior–septal PM approximations were performed. Echocardiographic, haemodynamic and sonomicrometry data were collected. RESULTS: Tricuspid regurgitation at baseline in eight sheep was none or trace in 3 and mild in 5, and after induction of acute right heart failure increased significantly to moderate in 5, moderately severe in 1 and severe in 2 (P = 0.011). RV pressure increased from 31 [28; 43] to 51 [47; 55] mmHg (P = 0.012). Anterior–posterior PM approximation decreased regurgitation grade to none or trace in 1, mild in 4 and moderate in 3 (P = 0.016) and reduced PM area from 208 [160; 241] to 108 [48; 181] mm(2) (P = 0.008), and anterior–posterior PM distance from 18 [16; 20] to 10 [7; 13] mm (P = 0.037). Anterior–septal approximation also significantly reduced PM area but had no effect on regurgitation grade. CONCLUSIONS: Anterior–posterior but not anterior–septal PM approximation alleviated acute ovine tricuspid regurgitation. Selective PM approximation may offer better control of tricuspid regurgitation.