Leaflet remodeling reduces tricuspid valve function in a computational model

Tricuspid valve leaflets have historically been considered "passive flaps". However, we have recently shown that tricuspid leaflets actively remodel in sheep with functional tricuspid regurgitation. We hypothesize that these remodeling-induced changes reduce leaflet coaptation and, therefore, contribute to valvular dysfunction. To test this, we simulated the impact of remodeling-induced changes on valve mechanics in a reverse-engineered computer model of the human tricuspid valve. To this end, we combined right-heart pressures and tricuspid annular dynamics recorded in an ex vivo beating heart, with subject-matched in vitro measurements of valve geometry and material properties, to build a subject-specific finite element model. Next, we modified the annular geometry and boundary conditions to mimic changes seen in patients with pulmonary hypertension. In this model, we then increased leaflet thickness and stiffness and reduced the stretch at which leaflets stiffen, which we call "transition-λ." Subsequently, we quantified mean leaflet stresses, leaflet systolic angles, and coaptation area as measures of valve function. We found that leaflet stresses, leaflet systolic angle, and coaptation area are sensitive to independent changes in stiffness, thickness, and transition-λ. When combining thickening, stiffening, and changes in transition-λ, we found that anterior and posterior leaflet stresses decreased by 26% and 28%, respectively. Furthermore, systolic angles increased by 43%, and coaptation area decreased by 66%; thereby impeding valve function. While only a computational study, we provide the first evidence that remodeling-induced leaflet thickening and stiffening may contribute to valvular dysfunction. Targeted suppression of such changes in diseased valves could restore normal valve mechanics and promote leaflet coaptation.

Papillary muscle approximation in chronic ovine functional tricuspid regurgitation

OBJECTIVE

Isolated tricuspid ring annuloplasty remains the surgical standard for functional tricuspid regurgitation repair but offers suboptimal results when right ventricular dilation and remodeling along with papillary muscle displacement is present. Addressing subvalvular remodeling with papillary muscle approximation may improve clinical outcomes.

METHODS

Functional tricuspid regurgitation and biventricular dysfunction were induced in 8 healthy sheep by rapid ventricular pacing (200-240 bpm) for 27 ± 6 days. Subsequently, animals underwent cardiopulmonary bypass for implantation of sonomicrometry crystals on the tricuspid annulus, right ventricle, and papillary muscle tips. Papillary approximation sutures were anchored between anterior-posterior and anterior-septal papillary muscles and externalized through right ventricular free wall to epicardial tourniquets. After weaning from cardiopulmonary bypass, sequential papillary muscle approximations were performed. Simultaneous hemodynamic, sonomicrometry, and echocardiographic data were collected at baseline and after each papillary muscle approximation.

RESULTS

With rapid pacing, right ventricular fractional area change decreased from 59 ± 6% to 38 ± 8% (P < .001), whereas tricuspid annulus diameter increased from 2.4 ± 0.3 cm to 3.3 ± 0.6 cm (P = .003). Tricuspid regurgitation (0-4+) increased from +0 ± 0 to +3.3 ± 0.7 (P < .001). Both anterior-posterior and anterior-septal papillary muscle approximation significantly reduced functional tricuspid regurgitation from +3.3 ± 0.7 to +2 ± 0.5 and +1.9 ± 0.6, respectively (P < .001). Reduction of tricuspid insufficiency with both subvalvular interventions was associated with decreased distance of the anterior papillary muscle to the annular centroid.

CONCLUSIONS

Papillary muscle approximations were effective in reducing severe ovine functional tricuspid regurgitation associated with right ventricular dilation and papillary muscle displacement. Further studies are needed to evaluate efficacy of this adjunct to ring annuloplasty in repair of severe functional tricuspid regurgitation.

Septal annular dilation in chronic ovine functional tricuspid regurgitation

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.

Tricuspid annular dynamics, not diameter, predicts tricuspid regurgitation after mitral valve surgery: Results from a prospective randomized trial

Objective

Current guidelines advise using prophylactic tricuspid valve annuloplasty during mitral valve surgery, especially in the presence of annular diameter enlargement. However, several retrospective studies and a prospective randomized study from our department could not confirm that diameter enlargement is predictive of late regurgitation. We examined whether 2- and 3-dimensional echocardiographic and clinical characteristics could identify patients who will develop moderate or severe recurrent tricuspid regurgitation.

Methods

Patients with less than severe functional tricuspid regurgitation (FTR) were randomized not to receive tricuspid annuloplasty, and 11 of 53 of them were excluded from the study because 3-dimensional echocardiographic analysis was not possible. Cox regression was used to estimate the model-based probability of moderate or severe FTR (vena contracta ≥3 mm) or progression of TR and FTR regression using valve dimensions (annulus area, diameter perimeter, nonplanar angle, and sphericity index), dynamics (annulus contraction, annulus displacement, and displacement velocity), and clinical parameters as possible predictors.

Results

At a median follow-up of 3.8 years (range, 3-5.6 years), 17 patients had moderate or severe FTR or progression, and 13 had FTR regression. Our models identified annular displacement velocity as a significant predictor for FTR recurrence and nonplanar angle as a significant predictor for FTR regression.

Conclusions

Annular dynamics, not the dimension, predict recurrence and regression of FTR. Annular contraction should be systematically investigated as a possible surrogate of right ventricle function to prophylactically treat the tricuspid valve.

Five-year outcomes of tricuspid valve repair versus replacement; a propensity score-matched analysis

BACKGROUND

Tricuspid valve repair (TVr) is the recommended approach for managing tricuspid regurgitation; however, there is a concern about the long-term durability of the repair. Therefore, this study aimed to compare the long-term outcomes of TVr versus tricuspid valve replacement (TVR) in a matched cohort of patients.

METHODS

This study included 1161 patients who underwent tricuspid valve (TV) surgery from 2009 to 2020. Patients were grouped according to the procedure into two groups: patients who underwent TVr (n = 1020) and patients who underwent TVR (n = 159). The propensity score identified 135 matched pairs.

RESULTS

Renal replacement therapy and bleeding were significantly higher in the TVR group compared to the TVr group both before and after matching. Thirty-day mortality occurred in 38 (3.79%) patients in TVr group versus 3 (1.89%) in the TVR group (P ≤ 0.001) but was not significant after matching. After matching, TV reintervention (hazard ratio (HR): 21.44 (95% CI: 2.17-211.95); P  =  0.009) and heart failure rehospitalization (HR: 1.89 (95% CI: 1.13-3.16); P  =  0.015) were significantly higher in the TVR group. There was no difference in mortality in the matched cohort (HR: 1.63 (95% CI: 0.72-3.70); P  =  0.25).

CONCLUSIONS

TVr was associated with lower renal impairment, reintervention, and heart failure rehospitalization than replacement. TVr remains the preferred approach whenever feasible.

Valvular complex and tissue remodelling in ovine functional tricuspid regurgitation

OBJECTIVES

Pathophysiology of function tricuspid regurgitation (FTR) is incompletely understood. We set out to comprehensively evaluate geometric and tissue remodelling 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. Haemodynamic 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). The mean TR grade (+0-4) was 0.8 ± 0.4 and 3.2 ± 1.2 (P = 0.0001) for control and banded animals, respectively. Right ventricle 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°, 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 remodelling to be associated with ovine functional tricuspid regurgitation. Durable surgical repair of severe FTR may require a multi-level approach to the valvular apparatus.

Developing Insights Regarding Tricuspid Valve Regurgitation: Morphology, Assessment of Severity, and the Need for a Novel Grading Scheme

Current understanding that progressive tricuspid regurgitation (TR) is associated with worse outcomes has highlighted the clinical need for a more accurate assessment of TR morphology and severity. This need has been further emphasized owing to the development of a myriad of percutaneous right-sided interventions, which may offer successful treatment of TR in selected patients. Understanding the etiology and quantification of the severity of TR has important implications in the selection of novel therapeutic strategies, i.e., medical vs. percutaneous vs. surgical approaches. Newer grading schemas that better reflect the TR lesion severity have been recently proposed and may facilitate monitoring of the evolution of TR following percutaneous and/or surgical treatment. In this review, we summarize contemporary concepts regarding tricuspid valve morphology, TR etiology, and associated mechanisms and echocardiographic approaches to grade TR severity.

Tricuspid Valve Anterior Leaflet Strains in Ovine Functional Tricuspid Regurgitation

Functional tricuspid regurgitation (FTR) is thought to arise due to annular dilation and alteration of right ventricular (RV) geometry in the presence of normal leaflets, yet mitral leaflets have been shown to remodel significantly in functional mitral regurgitation. We set out to evaluate tricuspid valve anterior leaflet deformations in ovine FTR. Eleven animals (FTR group) underwent implantation of a pacemaker with high rate pacing to induce biventricular dysfunction and at least moderate TR. Subsequently, both FTR (n = 11) and Control (n = 12) animals underwent implantation of 6 sonomicrometry crystals around the tricuspid annulus, 4 on the anterior leaflet, and 14 on RV epicardium. Tricuspid valve geometry and anterior leaflet strains were calculated from crystal coordinates. Left ventricular ejection fraction and RV fractional area change were significantly lower in FTR animals versus Control. Tricuspid annular area, septo-lateral diameter, RV pressures were all significantly greater in the FTR group. Mean TR grade (+0-3) was 0.7 ± 0.5 in Control and 2.4 ± 0.5 in FTR (P = < 0.001). The anterior leaflet area and length increased significantly. Global radial leaflet strain was significantly lower in FTR mostly driven by decreased free edge leaflet strain. Global circumferential anterior leaflet strain was also significantly lower in FTR with more remarkable reduction in the belly region. Rapid ventricular pacing in sheep resulted in a clinically pertinent model of RV and annular dilation with FTR and leaflet enlargement. Both circumferential and radial anterior leaflet strains were significantly reduced with FTR. Functional TR may be associated with alteration of leaflet mechanical properties.

Late tricuspid regurgitation and right ventricular remodeling after tricuspid annuloplasty

BACKGROUND

The aim of the present retrospective study was to evaluate the influence of preoperative right ventricular (RV) and tricuspid valve (TV) remodeling on the fate of tricuspid annuloplasty (TA) and right ventricle.

METHODS

From May 2009 to December 2015, 423 patients who had undergone TA for functional tricuspid regurgitation (TR) were included in the study. Residual and recurrent TR were defined as moderate or more TR at discharge and follow-up, respectively. RV remodeling was defined as RV dysfunction and/or dilation.

RESULTS

Residual TR after TA was recorded in 54 patients (13%). Five-year freedom from TR recurrence was 81% ± 3% in patients without residual TR and 41 ± 8 in patients with residual TR (P < .001). In patients without residual TR, the following risk factors for recurrent TR and late RV remodeling were identified: preoperative systolic pulmonary artery pressure, preoperative RV remodeling, severe preoperative TR or less than severe TR but with TV apparatus remodeling, and etiology of mitral regurgitation. Cox analysis with time-dependent variables confirmed TR recurrence (hazard ratio [HR]: 3.1) and late RV remodeling (HR: 6.5) as risk factors for lower survival. No protective effect of either flexible band or rigid ring TA compared with DeVega procedure was found. Similarly, preoperative atrial fibrillation and pacemaker dependency, late failure of mitral valve surgery did not affect the fate of TR.

CONCLUSIONS

Prophylactic TA should be encouraged among surgeons. TA at the time of left-sided valve surgery should take into consideration not only annular size, but also tethering severity and RV remodeling.