Effect of variable annular reduction on functional tricuspid regurgitation and right ventricular dynamics in an ovine model of tachycardia-induced cardiomyopathy

Objective: To investigate the effect of variable tricuspid annular reduction (TAR) on functional tricuspid regurgitation (FTR) and right ventricular (RV) dynamics in ovine tachycardia-induced cardiomyopathy. Methods: Nine adult sheep underwent implantation of a pacemaker with an epicardial lead and were paced at 200 to 240 bpm until the development of biventricular dysfunction and functional TR was noted. During reoperation on cardiopulmonary bypass, 6 sonomicrometry crystals were placed around the tricuspid annulus (TA) and 14 were placed on the RV epicardium. Annuloplasty suture was placed around the TA and externalized to an epicardial tourniquet. After weaning from cardiopulmonary bypass, echocardiographic, hemodynamic, and sonomicrometry data were acquired at baseline and during 5 progressive TARs achieved with suture cinching. TA area and RV free wall strains and function were calculated from crystal coordinates. Results: After pacing, changes in left ventricular (LV) ejection fraction and RV fractional area decreased significantly. Mean TA diameter increased from 25.1 +/- 2.9 mm to 31.5 +/- 3.3 mm (P = .005), and median TR (range, 0-3+) increased from 0 (0) to 3 (2) (P = .004). Progressive suture cinching reduced the TA area by 18 +/- 6%, 38 +/- 11%, 56 +/- 10%, 67 +/- 9%, and 76 +/- 8%. Only aggressive annular reductions (67% and 76%) decreased TR significantly, but these were associated with deterioration of RV function and strain. A moderate annular reduction of 56% led to a substantial reduction of TR with little deleterious effect on regional RV function. Conclusions: A moderate TAR of approximately 50% may be most advantageous for correction of functional TR and simultaneous maintenance of regional RV performance. Additional subvalvular interventions may be needed to achieve complete valvular competence.