Tricuspid valvular dynamics and 3-dimensional geometry in awake and anesthetized sheep

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.

The Early Effects on Tricuspid Annulus and Right Chambers Dimensions in Successful Tricuspid Valve Bicuspidization

BACKGROUND

It is unclear to what degree of tricuspid annulus (TA) reduction is necessary to achieve good postoperative results in surgical bicuspidization. The study aimed to evaluate TA and right heart chamber's dimensions before and after heart surgery; and to compare TA parameters assessed by different modalities.

METHODS

Forty patients underwent mitral valve surgery with or without concomitant tricuspid valve (TV) bicuspidization. Preoperative and postoperative measurements of TA dimensions were performed prospectively using two-dimensional (2D) and three-dimensional (3D) transthoracic echocardiography (TTE). Additionally, preoperative transesophageal echocardiography (TOE) was performed in the operating room prior to surgery.

RESULTS

All patients had no or mild TR immediately after surgery. There was a significant reduction in 2D and 3D parameters of the TV and right chambers in the TV bicuspidization group. However, TV leaflets' tethering parameters did not change significantly. Preoperative 3D TTE measurements were smaller than those obtained through 3D TOE in the operation room, before surgery under general anesthesia. The 2D systolic apical 4Ch diameter and the parasternal short axis diameter mainly represent the 3D minor axis of the TA and are smaller than its 3D major axis.

CONCLUSIONS

Although bicuspidization results in a one-third reduction of the TV area, tethering of the TV leaflets remains unchanged. Moreover, 3D TOE parameters of the TV under general anesthesia are larger than preoperative 3D TTE measurements. Conventional 2D measurements are insufficient for evaluating the maximum diameter of the TA.

Morphological and Dynamic Analysis of the Right Atrioventricular Junction in Healthy Subjects with 4D Computed Tomography

PURPOSE

To improve knowledge of the tricuspid valve and right atrioventricular junction (RAVJ) coupling, four-dimensional (4D) imaging is mandatory (3D + time). Based on multiphase cardiac-volume computed tomography (CT) and innovative 4D analysis, we proposed to assess dynamical features of tricuspid annulus (TA) in relation to the right ventricle (RV) and right atrial (RA) functions.

METHODS

Cardiac-volume CT data sets through time were obtained in 30 healthy patients (Male 57%, mean age 57 ± 11 years). Using an in-house software, 3D semi-automated delineation of 18 points around TA perimeter were defined through 10 cardiac phases within RR interval and used to calculate TA features such as 3D/2D areas, perimeters, 360°-diameters and vertical deformation. RV and RA inner contours were also delineated. Bi-dimensional parameters were compared with multiplanar reconstruction (MPR) measurements.

RESULTS

TA was elliptical in horizontal projection with a maximal eccentricity index (EcI_max) of 0.58 ± 0.12; and saddle-shaped in vertical projection with a horn nearby the antero-septal commissure. This feature remained throughout the cardiac cycle, but TA was more planar and less circular in late diastole (TA-height: 4.53 ± 1.06 mm, EcI_max = 0.61 ± 0.14) when TA 3D area and perimeter reached a maximum of 7.05 ± 1.23 and 7.48 ± 0.93cm/m², respectively. Correlations between minimal and maximal TA 3D areas and TA Projected 2D areas were excellent (r = 0.993 and r = 0.995, p < 0.001). TA 2D area measurements by MPR overestimated the projected values by 22 to 24%. Correlation between RV concentric strain and TA maximal diameter shortening was r = 0.452 (p = 0.01).

CONCLUSIONS

Cardiac-volume CT improves physiological knowledge of the relationships between the RAVJ components in healthy subjects.

Tricuspid leaflet kinematics after annular size reduction in ovine functional tricuspid regurgitation

OBJECTIVE

Tricuspid annular size reduction with annuloplasty rings represents the foundation of surgical repair of functional tricuspid regurgitation. However, the precise effect of annular size reduction on leaflet motion and geometry remains unknown.

METHODS

Ten sheep underwent surgical implantation of a pacemaker with an epicardial lead and were paced 200-240 beats/min to achieve biventricular dysfunction and functional tricuspid regurgitation. Subsequently, sonomicrometry crystals were implanted on the right ventricle, the tricuspid annulus, and on the belly of anterior, posterior, and septal tricuspid leaflets. Double-layer polypropylene suture was placed around the tricuspid annulus and externalized to a tourniquet. Simultaneous echocardiographic, hemodynamic, and sonomicrometry data were acquired with functional tricuspid regurgitation and during 5 consecutive annular reduction steps. Annular area, tenting height, and volume, together with each leaflet strain, radial length, and angles, were calculated from crystal coordinates.

RESULTS

Rapid pacing reduced both left ventricle and right ventricle function and induced functional tricuspid regurgitation (0-3+) in all animals (from 0 ± 0 to 2.4 ± 0.7, P = .002), whereas tricuspid annulus diameter increased from 2.6 ± 0.3 cm to 3.3 ± 0.3 cm (P = .001). Tricuspid annular size reduction 1 to 5 resulted in 16% ± 7%, 37% ± 11%, 55% ± 11%, 66% ± 10%, and 76% ± 8% tricuspid annulus area reduction, respectively, and successively decreased tricuspid regurgitation. Tricuspid annular size reduction 2 to 5 induced anterior and posterior leaflet restricted motion and lower diastolic motion velocities. Tricuspid annular size reduction 5 perturbed septal leaflet range of motion but preserved its angle velocities. Tricuspid annular size reduction 3-5 generated compressive strains in all leaflets.

CONCLUSIONS

Tricuspid annular area reduction of 55% perturbed anterior and posterior leaflet motion while maintaining normal septal leaflet movement. More extreme reduction triggered profound changes in anterior and posterior leaflet motion, suggesting that aggressive undersizing impairs leaflet kinematics.

Mid-term functional recovery after tricuspid annuloplasty concomitant with left-sided valve surgery

BACKGROUND

To elucidate the impact of tricuspid annuloplasty concomitant with left-sided valve surgery on the right ventricular (RV) function in patients with mild or more tricuspid regurgitation (TR).

METHODS

We enrolled 136 patients with mild or more TR who underwent left-sided valve surgery. Seventy-three patients underwent left-sided valve surgery alone (group non-T) and 63 underwent concomitant tricuspid annuloplasty (group T). The echocardiographic data at the latest follow-up (mean 1019 days) were compared using multiple regression analysis to adjust cofounding factors. Propensity score was calculated and included in the analysis as a covariate. In addition, propensity score matching was used for sensitive analysis (12 pairs).

RESULTS

In group non-T, there were more aortic valve surgeries, and fewer mitral valve surgeries. At baseline, body surface area, New York Heart Association class, and prevalence of atrial fibrillation were significantly different between groups. On preoperative echocardiography, left and right atrial diameter, RV diameter, and tricuspid annular diameter were larger in group T, whereas there was no significant difference in RV fractional area change. In multiple regression analyses, RV diameter in diastole was significantly lower and RV fractional area change was significantly higher at the follow-up period in group T. These results were not attenuated even in subgroup analysis in patients with only mild TR or mitral valve surgery alone.

CONCLUSION

Among patients with mild or more TR, RV dimensional and functional recovery was not obtained with left-sided valve surgery alone. Adding tricuspid annuloplasty may potentially achieve both outcomes.

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.

Tricuspid valve leaflet strains in the beating ovine heart

The tricuspid leaflets coapt during systole to facilitate proper valve function and, thus, ensure efficient transport of deoxygenated blood to the lungs. Between their open state and closed state, the leaflets undergo large deformations. Quantification of these deformations is important for our basic scientific understanding of tricuspid valve function and for diagnostic or prognostic purposes. To date, tricuspid valve leaflet strains have never been directly quantified in vivo. To fill this gap in our knowledge, we implanted four sonomicrometry crystals per tricuspid leaflet and six crystals along the tricuspid annulus in a total of five sheep. In the beating ovine hearts, we recorded crystal coordinates alongside hemodynamic data. Once recorded, we used a finite strain kinematic framework to compute the temporal evolutions of area strain, radial strain, and circumferential strain for each leaflet. We found that leaflet strains were larger in the anterior leaflet than the posterior and septal leaflets. Additionally, we found that radial strains were larger than circumferential strains. Area strains were as large as 97% in the anterior leaflet, 31% in the posterior leaflet, and 31% in the septal leaflet. These data suggest that tricuspid valve leaflet strains are significantly larger than those in the mitral valve. Should our findings be confirmed they could suggest either that the mechanobiological equilibrium of tricuspid valve resident cells is different than that of mitral valve resident cells or that the mechanotransductive apparatus between the two varies. Either phenomenon may have important implications for the development of tricuspid valve-specific surgical techniques and medical devices.

Tricuspid Valve Regurgitation Decreases after MitraClip Implantation: Fluid Structure Interaction Simulation

Untreated tricuspid valve regurgitation (TR) is associated with increased rates of mortality, morbidity, and hospitalization. Current pharmacological and surgical treatment options for TR are limited. MitraClip (MC), an edge-to-edge percutaneous intervention, has been reported to be effective for treatment of TR. The goal of this study was to examine the effects of MC position on TR, using a multiphysics fluid-structure-interaction (FSI) analysis. The computational set up included the tricuspid valve (TV), the chordae tendineae, the blood particles, and a tube that surrounded the leaflets and blood particles. The leaflets and chordae were modeled as hyperelastic materials, and blood was modeled using smoothed particle hydrodynamics. FSI analysis was conducted for blood flow through the closed valve for multiple simulations that account for normal, diseased, and treated conditions of the TV. To simulate the diseased TV, a group of chordae between septal and pulmonary leaflets were removed from the normal TV, which produced increased regurgitation. Four MC treated scenarios were considered: i) one MC near the annulus, ii) one MC approximately midway between the annulus and leaflet tip, iii) one MC near the leaflet tip, iv) two MCs: one approximately midway between the annulus and leaflet tip, and one close to the leaflet tip. The TR increased in diseased TV (7.5%) compared to normal TV (2.5%). All MC treated scenarios decreased TR. The MC located near the midway point between the annulus and leaflet tip led to largest decrease in TR (75.2% compared to the untreated condition). The MC located near the leaflet tip was associated with lowest reduction in TR (2.2% compared to the untreated condition). When two MCs were used, reduction in TR was relatively high (68.7%), but TR was not improved compared to the optimal single MC. MC caused high stresses in the vicinity of the clipping area in all conditions; the highest occurred when the MC was near the leaflet tips. Using a quantitative computational approach, we confirm previous clinical reports on the efficacy of MC for treatment of TR. The results of this study could lead to the design of more efficient MC interventions for TR.

Tricuspid Valve Annular Mechanics: Interactions with and Implications for Transcatheter Devices

In the interventional treatment of tricuspid valve regurgitation, the majority of prosthetic devices interact with or are implanted to the tricuspid valve annulus. For new transcatheter technologies, there exists a growing body of clinical experience, literature, and professional discourse related to the difficulties in delivering, securing, and sustaining the function of these devices within the dynamic tricuspid annulus. Many of the difficulties arise from circumstances not encountered in open-heart surgery, namely; a non-arrested heart, indirect visualization, and a reliance on non-suture-based methods. These challenges require the application of procedural techniques or system designs to account for tricuspid annular motion, forces, and underlying tissue strength. Improved knowledge in these interactions will support the goals of improving device systems, their procedures, and patient outcomes. This review aims to describe current concepts of tricuspid annular mechanics, key device and procedural implications, and highlight current knowledge gaps for future consideration.