Abstract
Background
Tricuspid anteroposterior patch (TRAPP) repair aims to address shortcomings of traditional annuloplasty in functional tricuspid regurgitation by selectively enlarging and translocating the anterior and posterior leaflets, but optimal patch width has not been identified.
Methods
An ex vivo model of the tricuspid valve was established in fresh porcine hearts by pneumatic pressurization of the ventricles. TRAPP repair was performed with patches of varying width (group 1, 1.0 cm; group 2, 1.5 cm; group 3, 2.0 cm). A 3-dimensional structured light scanner was used to image the topography of the tricuspid valve before and after TRAPP repair, and measurements were compared.
Results
Coaptation length increased with TRAPP repair in all groups (group 1, 44% [P = .004]; group 2, 70% [P < .001]; group 3, 82% [P = .002]). Coaptation increases in length and area were similar in groups 2 and 3, but the larger patch size of group 3 caused bulging above the annulus and significant changes in leaflet measurements.
Conclusions
Optimal patch size for TRAPP repair is 1.5 cm. This patch size maximally increased coaptation length but avoided abnormal systolic leaflet geometry (bulging) seen with the larger patch.
In Short.
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Tricuspid anteroposterior patch (TRAPP) repair uses selective augmentation of the anterior and posterior leaflets of the tricuspid valve with a pericardial patch to address functional tricuspid regurgitation.
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The findings of this study support a 1.5-cm pericardial patch in TRAPP repair to provide maximal supernormal coaptation without compromising valve geometry.
Functional tricuspid regurgitation (FTR) results from geometric abnormalities of the tricuspid apparatus, including annular dilation and leaflet tethering, that occur with normal tricuspid valve (TV) leaflets.1 Annuloplasty is the most common operation for FTR but can be ineffective for patients with massive or torrential FTR or leaflet tethering and carries a significant risk of permanent pacemaker placement.2,3
Our group has previously described mitral valve translocation, which addresses functional mitral regurgitation through circumferential pericardial patch augmentation.4, 5, 6 Based on this experience, we have adapted mitral valve translocation to treat FTR through selective augmentation of the anterior and posterior leaflets, developing tricuspid anteroposterior patch (TRAPP) repair. This study uses an ex vivo model to evaluate optimal patch size for TRAPP repair.
Material and Methods
Ex Vivo Model
Nineteen swine hearts (397 ± 27 g) were included in the study. Fresh swine hearts were acquired from an abattoir (ATSCO, Inc). The aorta and pulmonary artery were first dissected and both atria excised just above the annuli to expose the atrioventricular valves. The coronary arteries were ligated. The ascending aorta and pulmonary artery were cross-clamped and cannulated proximally. The cannulas were secured with a purse-string and directed into the right and left ventricles. Once secured, these cannulas provided pneumatic pressurization to the ventricles from a 38-W linear-drive air pump (Gardner Denver Thomas). The right ventricle was pressurized to 30 mm Hg and the left ventricle to 120 mm Hg to create a conformation similar to that of peak systole, with both the tricuspid and mitral valves closed (Supplemental Figure 1).
TRAPP Repair
For each heart, the distance from the anteroseptal to posteroseptal commissures along the anterior and posterior leaflet annuli was measured (Figure 1A). A partial frustum-shaped patch was constructed from bovine pericardium (Wagner Meats) using the measured annular length as the annular suture line length for the patch. The width of the patch was varied: group 1, 1.0 cm (n = 5); group 2, 1.5 cm (n = 5); and group 3, 2.0 cm (n = 6). The patch was oriented to create a partial frustrum with pointed edges for implantation (Figure 1B).
Figure 1.
Tricuspid anteroposterior patch TRAPP repair patch design and implantation. (A) The annulus is both measured and cut along these dimensions between the anteroseptal and posteroseptal commissures (dashed line). This distance is used as the annular suture line length for the patch. (B) The TRAPP repair patch was designed as a partial frustum with curved corners. Width varied between 1.0 cm (group 1), 1.5 cm (group 2), and 2.0 cm (group 3). (C) The patch was implanted along the annulus between the anteroseptal and posteroseptal commissures.
The anterior and posterior leaflets were subsequently partially detached from the annulus between the anteroseptal and posteroseptal commissures. The subvalvular apparatus was left intact. The patch was implanted between the leaflet and annulus (Figure 1C).
Image Acquisition
A 3-dimensional (3D) structured light scanner (Artec 3D) was used to capture the topography of the pressurized and closed TV through light triangulation to create a 3D point cloud and to generate a finite element mesh. This mesh was exported to a scan to computer-aided design software (Geomagic DesignX; 3D Systems). This software allows the marking and measurement of the TV in 3D space with color and texture overlying the mesh.
Study Definitions and Outcomes
The primary outcomes of this study were comparisons between the native and TRAPP repair states for annular, leaflet, and coaptation measurements. Systolic measurements were taken with the right ventricle pressurized and the TV closed. Annular and leaflet measurements for each TV leaflet were taken (Supplemental Figure 2A). Coaptation length and area were calculated with multiple dye lines (Wilton). Coaptation length was averaged across 21 points on the leaflet (Supplemental Figure 2B) and stratified by leaflet. Diastolic measurements were taken when the right ventricle was not pressurized and the TV was open.
Statistical Analysis
Paired t-tests were used to compare measurements in the native state and after TRAPP repair. Analysis of variance testing was performed to compare mean mass and time to completion between groups. Data are displayed as mean ± SD. All statistical analyses were performed with R statistical software version 3.6.2 (R Foundation for Statistical Computing) within RStudio statistical software version 1.2.5033 (RStudio).
Results
Swine hearts were randomly assigned to group 1 (1.0 cm [n = 5]), group 2 (1.5 cm [n = 5]), or group 3 (2.0 cm [n = 6]). Mean mass was 402 ± 38 g (group 1), 398 ± 22 g (group 2), and 391 ± 24 g (group 3; P = .82). Representative images are shown in Figure 2. Time to complete TRAPP repair was 25.2 ± 2.9 minutes (group 1), 26.5 ± 2.3 minutes (group 2), and 28.7 ± 3.2 minutes (group 3; P = .16).
Figure 2.
Representative images from 1.0, 1.5, and 2.0 cm. Tricuspid anteroposterior patch (TRAPP) repair in native, TRAPP repair and explant. Images are from 3-dimensional light scanner for the native, TRAPP repair and explant, with photographs also included (right side of TRAPP repair panel) for TRAPP repair. Coaptation changes are marked with dye.
Remaining measurements are reported as native vs TRAPP repair. Annular circumference increased with TRAPP repair in group 1 (121.1 ± 6.3 mm [native] to 126.5 ± 4.6 mm [TRAPP repair]; P = .03) and in group 2 (127.1 ± 12.1 mm to 133.6 ± 8.9 mm; P = .01) but not in group 3. Annular area did not change with TRAPP repair in any group (Supplemental Table 1).
Measurements for the septal, posterior, and anterior leaflets are detailed in Table 1. In group 1, septal tenting angle increased (P = .04), whereas posterior tenting angle decreased (P = .001) between the native state and TRAPP repair. All other leaflet measurements for group 1 were similar before and after TRAPP repair. Group 2, after TRAPP repair, had increased septal tenting angle (P = .03) and decreased posterior tenting angle (P = .002), and tenting area was decreased in both the septal (P = .04) and anterior (P = .002) leaflets. Group 3 had decreased tenting height in all leaflets (all P < .001), decreased tenting angles in the anterior and posterior leaflets (both P < .001), and decreased tenting area in all leaflets (all P < .05). Multiple measurements in group 3 were reported as zero because of leaflet bulging above the plane of the annulus.
Table 1.
Leaflet Measurements of Tricuspid Valve in Native State and After Tricuspid Anteroposterior Patch (TRAPP) Repair
| Measurement | Time Point | Group 1 | Group 2 | Group 3 |
|---|---|---|---|---|
| Septal tenting height, mm | Native | 5.1 ± 1.3 | 7.4 ± 1.1 | 8.7 ± 3.4 |
| TRAPP repair | 5.8 ± 2.2 | 7.6 ± 1.5 | 3.1 ± 3.9 | |
| P value | .23 | .73 | <.001 | |
| Septal tenting angle, degrees | Native | 19.7 ± 3.3 | 22.6 ± 2.6 | 32.4 ± 6.6 |
| TRAPP repair | 28.3 ± 5.4 | 32.7 ± 7.9 | 31.3 ± 6.7 | |
| P value | .04 | .03 | .67 | |
| Septal tenting area, mm2 | Native | 85.5 ± 17.0 | 138.0 ± 41.8 | 135.8 ± 59.5 |
| TRAPP repair | 72.1 ± 42.7 | 96.5 ± 42.8 | 39.2 ± 57.2 | |
| P value | .41 | .04 | .03 | |
| Posterior tenting height, mm | Native | 8.4 ± 2.5 | 11.6 ± 1.0 | 11.0 ± 2.7 |
| TRAPP repair | 7.4 ± 2.2 | 10.7 ± 1.2 | 0.0 ± 0.0a | |
| P value | .19 | .16 | <.001 | |
| Posterior tenting angle, degrees | Native | 37.9 ± 5.3 | 47.8 ± 4.8 | 40.6 ± 12.5 |
| TRAPP repair | 27.9 ± 7.2 | 35.6 ± 2.6 | 0.0 ± 0.0a | |
| P value | .001 | .002 | <.001 | |
| Posterior tenting area, mm2 | Native | 174.5 ± 49.5 | 240.8 ± 23.8 | 189.2 ± 108.4 |
| TRAPP repair | 165.5 ± 76.0 | 216.4 ± 74.5 | 0.0 ± 0.0a | |
| P value | .72 | .43 | .01 | |
| Anterior tenting height, mm | Native | 7.6 ± 2.2 | 10.0 ± 1.2 | 12.4 ± 3.1 |
| TRAPP repair | 8.2 ± 1.6 | 9.4 ± 2.1 | 0.0 ± 0.0a | |
| P value | .45 | .32 | <.001 | |
| Anterior tenting angle, degrees | Native | 19.8 ± 5.2 | 28.2 ± 6.3 | 29.2 ± 7.2 |
| TRAPP repair | 22.2 ± 6.0 | 22.7 ± 7.0 | 0.0 ± 0.0a | |
| P value | .52 | .12 | <.001 | |
| Anterior tenting area, mm2 | Native | 226.2 ± 100.5 | 239.1 ± 51.4 | 266.9 ± 47.4 |
| TRAPP repair | 163.0 ± 73.2 | 145.7 ± 64.2 | 0.0 ± 0.0a | |
| P value | .30 | .002 | <.001 |
Values are reported as mean ± SD. Native and TRAPP repair measurements were compared by paired 2-tailed t-test.
If leaflet tissue extended above the annular plane for the entirety of the selected axis, tenting angle, height, and area were set to zero.
Coaptation length and area increased with TRAPP repair in all groups (Table 2). Overall coaptation length increased in all groups and across all individual leaflets. Coaptation area increased by 43% in group 1 (P = .001), 126% in group 2 (P < .001), and 113% in group 3 (P < .001). There were no differences in diastolic measurements in any groups (Supplemental Table 2).
Table 2.
Coaptation Measurements of Tricuspid Valve in Native State and After Tricuspid Anteroposterior Patch (TRAPP)Repair
| Measurement | Time Point | Group 1 | Group 2 | Group 3 |
|---|---|---|---|---|
| Coaptation length, mm | Native | 4.8 ± 0.9 | 5.0 ± 0.8 | 3.9 ± 0.6 |
| TRAPP repair | 6.9 ± 1.1 | 8.4 ± 0.9 | 7.1 ± 1.4 | |
| Percentage change | 44% | 70% | 82% | |
| P value | .004 | <.001 | .002 | |
| Coaptation area, mm2 | Native | 659.1 ± 173.0 | 543.4 ± 219.3 | 495.8 ± 135.6 |
| TRAPP repair | 945.9 ± 227.0 | 1227.8 ± 282.3 | 1058.4 ± 183.4 | |
| Percentage change | 44% | 126% | 113% | |
| P value | .001 | <.001 | <.001 | |
| Coaptation length, septal | Native | 3.2 ± 1.3 | 4.0 ± 0.9 | 2.9 ± 1.1 |
| TRAPP repair | 4.9 ± 1.4 | 6.3 ± 0.6 | 5.2 ± 1.6 | |
| Percentage change | 53% | 58% | 79% | |
| P value | .01 | .02 | .02 | |
| Coaptation length, anterior | Native | 5.6 ± 1.4 | 5.5 ± 1.7 | 3.9 ± 1.4 |
| TRAPP repair | 8.2 ± 2.2 | 10.5 ± 1.1 | 7.4 ± 2.6 | |
| Percentage change | 46% | 91% | 90% | |
| P value | .003 | <.001 | .02 | |
| Coaptation length, posterior | Native | 5.6 ± 1.6 | 5.5 ± 1.6 | 4.9 ± 1.5 |
| TRAPP repair | 7.7 ± 1.5 | 8.5 ± 1.9 | 8.7 ± 2.1 | |
| Percentage change | 38% | 55% | 78% | |
| P value | .02 | <.001 | .002 |
Values are reported as mean ± SD. Native and TRAPP repair measurements were compared by paired 2-tailed t-test.
Comment
This study evaluated the optimal patch size for TRAPP repair in an ex vivo pneumatic porcine model, identifying a 1.5-cm patch as maximizing coaptation length and area without significantly altering valve geometry. Further increasing patch size to 2.0 cm did not additionally increase coaptation and was associated with bulging.
TRAPP repair resulted in increased coaptation length and area in all groups. FTR is associated with a pathologic decrease in coaptation,7 so procedures that increase coaptation are more likely to be effective in treating FTR. In this study, we uniformly observed a dramatic increase in coaptation with TRAPP repair extending to each individual leaflet. Although there were substantial increases in the coaptation length and area between group 1 and group 2, there was no additive increase from group 2 to group 3. Thus, the value of increasing patch width on coaptation extends to 1.5 cm, with diminishing returns for the 2-cm patch.
Preservation of annular, leaflet, and diastolic geometry is also important in maintaining valve function, and minimal changes were observed in these characteristics for groups 1 and 2. Group 3 had significant changes in leaflet measurements, reflecting the substantial billowing observed, with the patch extending above the annulus and eliminating almost all tenting. Diastolic measurements were similar before and after TRAPP repair across groups, suggesting that this repair does not have a negative impact on diastolic function. Annular circumference was slightly increased in groups 1 and 2, but these differences were small and were not reflected in changes in area, suggesting that there may have been a mild change in circularity rather than major annular dilation. Overall, the 1.0- and 1.5-cm patches had preserved annular, leaflet, and diastolic geometry, supporting their use in maintaining valve function.
There are several important limitations to consider in this study. First, this study uses a static model, which does not replicate the complex dynamics of the cardiac cycle. However, measurements were performed in both pressurized and unpressurized states to simulate systole and diastole, respectively. In addition, these repairs were not performed in an FTR model; thus, following this optimization study, future investigations should assess TRAPP repair in an FTR model to compare its efficacy with that of annuloplasty. Next, there are differences between porcine and human cardiac anatomy,8 but differences in the TV anatomy are small and primarily limited to the subvalvular apparatus,9 which is not altered in this study. Similar ex vivo models have previously been validated for the mitral valve,10 supporting the use of such models for the TV.
In conclusion, the findings of this study support the use of a 1.5-cm patch in TRAPP repair to provide supranormal coaptation without compromising valve geometry. The increased coaptation observed with the TRAPP repair may prove clinically valuable in the treatment of FTR. Future studies are needed to compare TRAPP repair with other FTR repairs and to evaluate TRAPP repair in vivo and clinically.
Acknowledgments
The Supplemental Material can be viewed in the online version of this article [https://doi.org/10.1016/j.atssr.2023.12.002] on http://www.annalsthoracicsurgery.org.
Funding Sources
Emily Larson: supported (in part) by an Alpha Omega Alpha Carolyn L. Kuckein student research fellowship. Hannah Rando: AHA grant #908805.
Disclosures
The authors have no conflicts of interest to disclose.
Supplementary Data
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