Septal annular dilation in chronic ovine functional tricuspid regurgitation

Abstract

Introduction: Annular reduction with prosthetic rings represents the current surgical treatment of functional tricuspid regurgitation (FTR). However, alterations of annular geometry and dynamics associated with FTR are not well characterized.

Methods: FTR was induced in 29 adult sheep with either 8 weeks of pulmonary artery banding (PAB, n = 15) or 3 weeks of tachycardia-induced cardiomyopathy (TIC, n = 14). Eight healthy sheep served as controls (CTL). At the terminal procedure, all animals underwent sternotomy, epicardial echocardiography, and implantation of sonomicrometry crystals on the tricuspid annulus (TA) and right ventricular free wall while on cardiopulmonary bypass. Simultaneous hemodynamic, sonomicrometry, and echocardiographic data were acquired after weaning from cardiopulmonary bypass and stabilization. Annular geometry and dynamics were calculated from 3-dimensional crystal coordinates.

Results: Mean FTR grade (0-4) was 3.2 ± 1.2 and 3.2 ± 0.5 for PAB and TIC, respectively, with both models of FTR associated with similar degree of right ventricular dysfunction (right ventricular fractional area contraction 38 ± 7% and 37 ± 9% for PAB and TIC, respectively). Left ventricular ejection fraction was significantly reduced in TIC versus baseline (33 ± 9%, vs 58 ± 4%, P = .0001). TA area was 651 ± 109 mm², 881 ± 242 mm², and 995 ± 232 mm² for CTL, FTR, and TIC, respectively (P = .006) with TA area contraction of 16.6 ± 4.2%, 11.5 ± 8.0%, and 6.0 ± 4.0%, respectively (P = .003). Septal annulus increased from 33.8 ± 3.1 mm to 39.7 ± 6.4 mm and 43.1 ± 3.2 mm for CTL, PAB, and TIC, respectively (P < .0001).

Conclusions: Ovine FTR was associated with annular dilation and reduced annular area contraction. Significant dilation of septal annulus was observed in both models of FTR. As tricuspid rings do not completely stabilize the septal annulus, continued remodeling may contribute to recurrent FTR after repair.

Keywords: functional tricuspid regurgitation; tricuspid valve; valve repair.

Figure 1.

Schematic representation of the right ventricle with implanted sonomicrometry crystals (orange spheres) around the tricuspid annulus and on the right ventricular epicardium. Crystals #1–2-3 correspond to the anterior annulus, #3–4-5 to the posterior annulus, and #5–6-1 to the septal annulus.

Figure 2.

Group mean and standard deviation data for tricuspid annular area (top panel) and tricuspid annular perimeter (bottom panel) throughout the cardiac cycle in control (CTL=8 [black line]), pulmonary artery banding (PAB=15 [dashed blue line]) and tachycardia-induced cardiomyopathy (TIC=14 [dashed orange line]) animals. ED= end-diastole, EIVC= end-isovolumic contraction, ES= end-systole, EIVR= end-isovolumic contraction.

Figure 3.

Group mean and standard deviation data for anterior (top panel), posterior (middle panel) and septal (bottom panel) annular perimeter throughout the cardiac cycle in control (CTL=8 [black line]), pulmonary artery banding (PAB=15 [dashed blue line]) and tachycardia-induced cardiomyopathy (TIC=14 [dashed orange line]) animals. ED= end-diastole, EIVC= end-isovolumic contraction, ES= end-systole, EIVR= end-isovolumic contraction.

Figure 4.

Tricuspid annular strain for control (CTL=8 [top panel]), pulmonary artery banding (PAB=15 [middle panel]) and tachycardia-induced cardiomyopathy (TIC=14 [bottom panel]) animals at end-diastole (ED), end-isovolumic contraction (EIVC), end-systole (ES), and end-isovolumic relaxation (EIVR) versus maximal diastolic annular size. AS= anterior septal commissure, AP= anterior-posterior commissure, and PS= posterior septal commissure. Red color indicates contraction, blue elongation.

Figure 5.

Graphic summary of experimental methods and key findings of the study

Central Picture

Septal annulus throughout the cardiac cycle in CTL, PAB, and TIC animals.