Objectives Reductive ring annuloplasty of the tricuspid annulus represents the contemporary surgical approach to functional tricuspid regurgitation (FTR). We set out to investigate the influence of moderate reductive tricuspid ring annuloplasty on tricuspid regurgitation and right ventricular (RV) size, geometry, and strain in an ovine model of chronic functional tricuspid regurgitation. Methods Eight healthy Dorsett male sheep (62.8 + 2kg) underwent a left thoracotomy for placement and tightening of pulmonary artery band to at least double proximal pulmonary artery blood pressure. After 8 weeks of recovery, animals underwent sternotomy, epicardial echocardiography, and sonomicrometry crystal implantation. Six crystals were place around tricuspid annulus, and 13 on right ventricular free wall epicardium along 3 parallels defining three wall regions (basal, mid, and lower), and one on the RV apex. All animals underwent beating heart implantation of 26 mm MC3 annuloplasty ring during a second CPB run after baseline data acquisition. Simultaneous haemodynamic, sonomicrometry, and echocardiography data were acquired at Baseline and after reductive tricuspid ring annuloplasty (TRA). Results Implantation of reductive ring annuloplasty resulted in 47 ± 7% annular area reduction (996 ± 152 mm vs 516 ± 52mm2, p = 0.0002) and significantly decreased RV end-diastolic volume (185 ± 27 vs 165 ± 30 ml, p = 0.02). TRA effectively reduced FTR grade (3.75 ± 0.6 vs 0.3 ± 0.5, p = 0.00004) and had little influence on RV function, cross-sectional area, radius of curvature, or free wall regional strains. Conclusion In adult sheep with 8 weeks of pulmonary artery banding and functional tricuspid regurgitation, tricuspid annulus reduction of 47% with prosthetic ring annuloplasty effectively abolished FTR while maintaining regional right ventricular function and strain patterns.

Introduction Del Nido cardioplegia (DN) is gaining acceptance in adult cardiac surgery but there is paucity of experimental data regarding its efficacy. We set out to assess the safety and efficacy of single-dose DN with and without topical cooling (TC) versus multi-dose blood cardioplegia (BC). Methods Thirty-two healthy adult sheep had pressure-volume (PV) catheters placed in the left (LV) and right (RV) ventricle. Animals were assigned to receive cold (4°C) antegrade solution for a 60-min arrest using: (1) multi-dose (every 20 min) BC with TC ( n = 11), (2) single-dose DN with TC (DN-C, n = 10), or (3) single-dose DN without TC (DN-H, n = 11). LV and RV PV-derived indexes, epicardial echocardiographic strains, and blood samples were acquired before CPB and at 1, 2, and 3 h of reperfusion. Dobutamine bolus (2.5 μg) was given after 3 h to test for myocardial reserve. Results Time to rhythm restoration was shortest (54 ± 29 s, 118 ± 167 s, and 172 ± 170 s for DN-H, DN-C, and BC, respectively; p = 0.024) and number of shocks lowest (1.7 ± 1.8, 3.6 ± 2.8, and 5.6 ± 4.6 for DN-H, DN-C, and BC, respectively; p = 0.020) in DN-H group. Hemodynamic, load-independent myocardial function, echocardiographic, and metabolic data revealed only slight differences between groups. Troponin I levels did not differ between groups. With dobutamine, preload-recruitable stroke work of both LV (136 ± 50%, 131 ± 31%, 142 ± 58% for BC, DN-C and DN-H, respectively; p = 0.993) and RV (161 ± 67%, 185 ± 45%, 166 ± 75% for BC, DN-C and DN-H respectively; p = 0.580) increased similarly. Conclusions Single-dose DN cardioplegia with or without topical cooling offered comparable biventricular myocardial protection to multi-dose BC for a 60-min arrest in sheep.

Background Pathophysiology of function tricuspid regurgitation (FTR) is incompletely understood. We set out to comprehensively evaluate geometric and tissue remodeling of the tricuspid valve complex in ovine FTR. Methods Twenty adult sheep underwent left thoracotomy and pulmonary artery banding (PAB) to induce right heart pressure overload and FTR. After 8 weeks, 17 surviving animals and 10 healthy controls (CTL) underwent sternotomy, echocardiography, and implantation of sonomicrometry crystals on right ventricle and tricuspid valvular apparatus. Hemodynamic and sonomicrometry data were acquired in all animals after weaning from cardiopulmonary bypass. Leaflet tissue was harvested for pentachrome histologic analysis and biomechanical testing. Results Animal weight was 62±5 and 63±3 kg for CTL and PAB, respectively (p = 0.6). At terminal procedure, systolic pulmonary artery pressure was 22±3 and 40±7 mmHg for CTL and PAB, respectively (p = 0.0001). Mean TR grade (+0-4) was 0.8±0.4 and 3.2±1.2 (p = 0.0001) for control and banded animals, respectively. RV volume (126±13 vs 172±34 ml, p = 0.0019), tricuspid annular area (651±109 vs 865±247 mm2, p = 0.037), and area between papillary muscle tips (162±51 vs 302±75 mm2, p = 0.001) increased substantially while systolic excursion of anterior leaflet decreased significantly (23.8±6.1 vs 7.4±4.5 deg, p = 0.001) with banding. Total leaflet surface area increased from 806±94 to 953±148 mm2 (p = 0.009), and leaflets became thicker and stiffer. Conclusions Detailed analysis of the tricuspid valve complex revealed significant ventricular, annular, subvalvular, and leaflet remodeling to be associated with ovine functional tricuspid regurgitation. Durable surgical repair of severe FTR may require a multi-level approach to the valvular apparatus.