TY - JOUR
AU - Hwang, Ho Young
AB - Abstract Open in new tabDownload slide Open in new tabDownload slide OBJECTIVES This study was conducted to measure suture tie-down forces and evaluate cyclic contractile forces (CCFs) in beating hearts after undersized 3-dimensional (3D) rigid-ring tricuspid valve annuloplasty (TAP). METHODS Eight force transducers were attached to the 3D rigid TAP ring. Segments 1 to 8 were attached from the mid-septal to anterior-septal commissural area in a counterclockwise order. Two-sizes-down ring TAPs were performed in 6 sheep. Tie-down forces and CCF were recorded and analysed at the 8 annular segments and at 3 levels of peak right ventricular pressure (RVP: 30, 50 and 70 mmHg). RESULTS The overall average tie-down forces and CCF were 4.34 ± 2.26 newtons (N) and 0.23 ± 0.09 N, respectively. The CCF at an RVP of 30 mmHg were higher at 3 commissural areas (segments 3, 5 and 8) than at the other segments. The increases in the CCF following changes in the RVP were statistically significant only at the 3 commissural areas (P = 0.012). However, mean CCFs remained low at all annular positions (ranges of average CCF = 0.06–0.46 N). CONCLUSIONS The risk of suture dehiscence after down-sized 3D rigid-ring TAP might be minimal because the absolute forces remained low in all annular positions even in the condition of high RVP. However, careful suturing in the septal annular area and commissures is necessary to prevent an annular tear during a down-sized 3D rigid-ring TAP. Tricuspid valve, Tricuspid valve annuloplasty, Annuloplasty ring dehiscence INTRODUCTION Tricuspid valve annuloplasty (TAP) is a preferred surgical procedure for patients with functional tricuspid regurgitation (TR). Previous studies have demonstrated that surgical outcomes of TAP using prosthetic rings are better than those of TAP using sutures in terms of TR recurrence [1–3]. Various rings have been introduced for TAP with pros and cons for each ring [4–7]. The 3-dimensional (3D) rigid ring (MC3 annuloplasty ring, Edwards Lifesciences, Irvine, CA, USA) is one such prosthetic ring that has exhibited favourable outcomes after TAP [5, 8, 9]. However, there is a concern that rigid rings pose a risk of ring dehiscence [10], which can occur while fixing the ring to the annulus or when the heart is beating after the ring is implanted. Therefore, this study was conducted to measure suture tie-down forces during ring implantation and to evaluate cyclic contractile forces (CCFs) in beating hearts after undersized 3D rigid ring TAP in an ovine model. MATERIALS AND METHODS Experimental animals Six 5-year-old male Corriedale sheep (57.3 ± 3.5 kg) were used in this study. They received care in compliance with the protocols approved by the institutional animal care and use committee of our institution (approval number: 800-20180451) in accordance with human care guidelines. Suture force transducers A strain-gauge-based transducer was designed to isolate the tensile forces of the sutures. Two holes mounted in the transducer’s frame allowed each device to be directly sutured to an annuloplasty ring to mimic a common ring annuloplasty technique. The apparatus consisted of 8 small 3D-printed specimens using a strain gauge (CEA-06-062UW-350, Vishay Micro-Measurements, Raleigh, NC, USA) to measure the strain at each location around the ring. Eight transducers were marked as segments 1 to 8: segments 1, 2 and 3 were placed at the septal annular area; segments 4 and 5, at the posterior annular area; and segments 6–8 at the anterior annular area (Fig. 1). Dimensions and materials (HP 3D High Reusability PA 12, HP Development Company, L.P., Houston, TX, USA) of these specimens were selected to ensure that the force deformation would not cause any permanent damage to the apparatus. To calibrate the transducer, a customized force calibration device was designed (Fig. 2). This device consisted of a force measurement sensor (DFS-BTA, Vernier, Beaverton, OR, USA), a linear actuator, a stepper motor (PKA544KD, Oriental Motor, Tokyo, Japan), and 5.6-inch industrial embedded computer (IEC 1000 Lite Series, HNS, Seoul, Korea), and a user interface that controlled the device (Fig. 2). First, the specimen was fixed on a holder connected to the actuator using the same polyester suture material (2–0 Ethibond, Ethicon, Somerville, NJ, USA) used in the animal experiment. Second, as the linear actuator moved at a constant speed of 0.1 mm/s, specimen distances from the force sensor also increased because of the force applied to the specimen by increased suture tension. The strain and force data were acquired using the Data Acquisition (DAQ) device NI9236 and USB6009 (National Instruments, Austin, TX, USA), followed by a LabView (National Instruments, Austin, TX, USA)-based software program to save and monitor data. Thereafter, the recorded data were used to construct the linear calibration curve. Because the strain gauge was attached to the parts manually, every part was calibrated separately to obtain a precise force-strain calibration curve. Figure 1: Open in new tabDownload slide (A) A schematic of a transducer with (a) holes for a ring mounting and (b) mattress suture passages. (B) Completed transducer. Figure 1: Open in new tabDownload slide (A) A schematic of a transducer with (a) holes for a ring mounting and (b) mattress suture passages. (B) Completed transducer. Figure 2: Open in new tabDownload slide (A) The calibration device. (B) Schematic of the calibration procedure: the distance between the specimen and the force sensor differs because the holder moves at a constant velocity inducing the strain change. Figure 2: Open in new tabDownload slide (A) The calibration device. (B) Schematic of the calibration procedure: the distance between the specimen and the force sensor differs because the holder moves at a constant velocity inducing the strain change. In vivo experimental protocol Each sheep was medicated with ketamine (25 mg/kg intramuscular injection), intubated and mechanically ventilated. General anaesthesia was induced with inhalational isoflurane (1.5–2%) and oxygen. The surface electrocardiogram and arterial blood pressure were monitored continuously during the experiment. The pericardial cavity was entered via a right thoracotomy, and cardiopulmonary bypass was established with systemic heparinization. The arterial cannula was placed in the right common carotid artery, and venous cannulae were inserted directly into the superior and inferior vena cavae. After initiating cardioplegic arrest using the Custodiol histidine-tryptophan-ketoglutarate solution (Koehler-Chemie, Mensheim, Germany), a right atriotomy was performed. The actual annular size was measured using ring sizers, and a ring 2 sizes smaller than the measured size was selected for the experiment. Eight 2–0 polyester sutures were placed in the tricuspid annulus. The ring was implanted and secured using annular sutures through the mounting holes of the transducer measurement arms. Before the ring was lowered and secured into the tricuspid annulus, each transducer was zeroed to establish a zero-force baseline. Annular mattress sutures were then tied to the ring by 1 surgeon from the mid-septal annulus to the anteroseptal commissure in a counterclockwise direction, and suture tie-down forces were recorded accordingly. After the animal was weaned from the cardiopulmonary bypass, the right ventricular pressure (RVP) was continuously measured and monitored using a high-fidelity pressure transducer. Continuous infusion and a bolus injection of an inotropic agent were used to maintain a peak RVP of 30 mmHg, 50 mmHg and 70 mmHg for at least 30 s for each CCF measurement. The animal was then euthanized by injecting 80 mEq of potassium chloride. The heart was removed and opened to verify the secure anchoring of the device to the annulus. Data collection and analysis During the experiment, the strain data were continuously acquired using the NI9236. From the data obtained, the maximum applied strain of each specimen was converted into a force by the designated calibrated curve in N units. To measure the average force applied to the specimens at different RVPs, the peaks and valleys of strain data due to heart contractions were detected by a customized code using the MATLAB programme (MathWorks, Natick, MA, USA). The 20 successive strain differences obtained from the absolute difference between these peak and valley values were averaged for each specimen. These averaged strain values were then converted to force using the assigned calibration curve. Statistical analyses Statistical analyses were performed using the IBM SPSS statistic software version 23.0 (IBM Inc., Armonk, NY, USA) and SAS version 9.4 (SAS Institute, Cary, NC, USA). Force measurements were presented as means ± standard deviations. Mean differences in suture tie-down forces between segments and between annular areas were compared using the linear mixed-effects model (LMM), with segments and annular areas as fixed effects and each normal ovine variation as a random effect to account for multiple measurements for each subject. An LMM with a random intercept was used because an LMM with a random intercept showed fit statistics (Akaike information criterion, Bayesian information criterion) similar to those of an LMM with a random intercept and a random segment. To compare the means of the CCFs, the interaction between peak RVP and segments was assessed using an LMM. When the interaction was not significant, the mean differences among segments or segment groups and among peak RVPs were compared using the main effect results in an LMM without interaction terms. The mean estimates from a model with main effects only were similar to those from a model with main effects and interaction terms (Supplementary Material, Table S1). The comparisons among segments or annular areas were each adjusted for peak RVP in an LMM. The comparison among peak RVPs was adjusted for segments in an LMM. The residual plots showed a random pattern, and their histograms revealed no severe violation of the normality assumption (Supplementary Material, Fig. S1A and B). The Bonferroni adjusted P-value was used for multiple comparisons. Mean estimates and 95% confidence intervals for segments, segment groups and peak RVP from LMMs are presented. A P-value of <0.050 was considered statistically significant. RESULTS Ring selection and measurement of suture tie-down forces A true tricuspid annulus measured 30 mm in all 6 sheep, and a 26-mm TAP ring was used in all experiments. Mean cardiopulmonary bypass and aortic cross-clamp times were 83 min and 54 min, respectively. The difference in suture tie-down forces was significant between segments (P < 0.001) (Table 1, Fig. 3). The average suture tie-down force was 4.34 ± 2.26 N. The lowest suture tie-down force was 2.23 ± 0.53 N at the anteroposterior commissure (segment 5), whereas the highest force was 7.67 ± 2.33 N at the mid-septal annulus (segment 1). The septal annular area (segments 1–3, 6.22 ± 1.93 N) had significantly higher force than the posterior (segments 4 and 5, 2.87 ± 2.07 N) and anterior annular areas (segments 6–8, 3.45 ± 1.25 N) (P < 0.001; Table 2, Fig. 3). Figure 3: Open in new tabDownload slide Suture tie-down force (A) at each position and (B) summations of forces at the septal, posterior and anterior annular areas. The force was significantly higher in the septal annular segments (6.22 ± 1.93 N) and lower at the posterior annular segments (2.87 ± 2.07 N; P < 0.0001). The bar graph depicts the mean and the 95% confidence interval of the suture tie-down force of each position and each annulus area. Figure 3: Open in new tabDownload slide Suture tie-down force (A) at each position and (B) summations of forces at the septal, posterior and anterior annular areas. The force was significantly higher in the septal annular segments (6.22 ± 1.93 N) and lower at the posterior annular segments (2.87 ± 2.07 N; P < 0.0001). The bar graph depicts the mean and the 95% confidence interval of the suture tie-down force of each position and each annulus area. Table 1: Mean and standard deviation of suture tie-down forces in each segment and in 3 annular areas Segments . Suture tie-down forces (N), mean ± SD . P-value . Segment 1 7.67 ± 2.33 <0.001 Segment 2 5.54 ± 1.36 Segment 3 5.45 ± 1.24 Segment 4 3.52 ± 2.86 Segment 5 2.23 ± 0.53 Segment 6 2.35 ± 0.91 Segment 7 4.61 ± 0.88 Segment 8 3.4 ± 0.78 Septal (segments 1–3) 6.22 ± 1.93 <0.001 Posterior (segments 4, 5) 2.87 ± 2.07 Anterior (segments 6–8) 3.45 ± 1.25 Total 4.34 ± 2.26 Segments . Suture tie-down forces (N), mean ± SD . P-value . Segment 1 7.67 ± 2.33 <0.001 Segment 2 5.54 ± 1.36 Segment 3 5.45 ± 1.24 Segment 4 3.52 ± 2.86 Segment 5 2.23 ± 0.53 Segment 6 2.35 ± 0.91 Segment 7 4.61 ± 0.88 Segment 8 3.4 ± 0.78 Septal (segments 1–3) 6.22 ± 1.93 <0.001 Posterior (segments 4, 5) 2.87 ± 2.07 Anterior (segments 6–8) 3.45 ± 1.25 Total 4.34 ± 2.26 N: newton; SD: standard deviation. Open in new tab Table 1: Mean and standard deviation of suture tie-down forces in each segment and in 3 annular areas Segments . Suture tie-down forces (N), mean ± SD . P-value . Segment 1 7.67 ± 2.33 <0.001 Segment 2 5.54 ± 1.36 Segment 3 5.45 ± 1.24 Segment 4 3.52 ± 2.86 Segment 5 2.23 ± 0.53 Segment 6 2.35 ± 0.91 Segment 7 4.61 ± 0.88 Segment 8 3.4 ± 0.78 Septal (segments 1–3) 6.22 ± 1.93 <0.001 Posterior (segments 4, 5) 2.87 ± 2.07 Anterior (segments 6–8) 3.45 ± 1.25 Total 4.34 ± 2.26 Segments . Suture tie-down forces (N), mean ± SD . P-value . Segment 1 7.67 ± 2.33 <0.001 Segment 2 5.54 ± 1.36 Segment 3 5.45 ± 1.24 Segment 4 3.52 ± 2.86 Segment 5 2.23 ± 0.53 Segment 6 2.35 ± 0.91 Segment 7 4.61 ± 0.88 Segment 8 3.4 ± 0.78 Septal (segments 1–3) 6.22 ± 1.93 <0.001 Posterior (segments 4, 5) 2.87 ± 2.07 Anterior (segments 6–8) 3.45 ± 1.25 Total 4.34 ± 2.26 N: newton; SD: standard deviation. Open in new tab Table 2: Results of linear mixed-effects model to compare suture tie-down forces between annuli Annular area . Differences of LSM (N) . 95% CI . Adjusted P-value . Septal vs posterior 3.345 2.031, 4.658 <0.001 Septal vs anterior 2.765 1.589, 3.940 <0.001 Posterior vs anterior −0.580 −1.894, 0.733 >0.999 Annular area . Differences of LSM (N) . 95% CI . Adjusted P-value . Septal vs posterior 3.345 2.031, 4.658 <0.001 Septal vs anterior 2.765 1.589, 3.940 <0.001 Posterior vs anterior −0.580 −1.894, 0.733 >0.999 a Values are presented as mean ± standard deviation. CI: confidence interval; LSM: least square means; N: newton. Open in new tab Table 2: Results of linear mixed-effects model to compare suture tie-down forces between annuli Annular area . Differences of LSM (N) . 95% CI . Adjusted P-value . Septal vs posterior 3.345 2.031, 4.658 <0.001 Septal vs anterior 2.765 1.589, 3.940 <0.001 Posterior vs anterior −0.580 −1.894, 0.733 >0.999 Annular area . Differences of LSM (N) . 95% CI . Adjusted P-value . Septal vs posterior 3.345 2.031, 4.658 <0.001 Septal vs anterior 2.765 1.589, 3.940 <0.001 Posterior vs anterior −0.580 −1.894, 0.733 >0.999 a Values are presented as mean ± standard deviation. CI: confidence interval; LSM: least square means; N: newton. Open in new tab Cyclic contractile force measurements At each position, real-time forces exhibited strong coupling to RVP and low inter-cycle variability (Fig. 4). Mean CCFs across all segments were 0.19 ± 0.17 N, 0.25 ± 0.16 N and 0.26 ± 0.21 N at the peak RVP of 30 mmHg, 50 mmHg and 70 mmHg, respectively. The CCFs were significantly different between segments (P < 0.001, Fig. 5, Table 3), i.e. lowest at the posterior annular area (segments 4 and 5, 0.17 ± 0.09 N) and highest at the septal area (segments 1, 2 and 3, 0.30 ± 0.08 N). The CCF of 3 commissural areas (segments 3, 5 and 8) were different from each other (P = 0.016), and the posteroseptal commissure (segment 3) was highest among the 3 commissural areas (P = 0.034). The 3 commissural areas (segments 3, 5 and 8) had significantly higher CCF than other segments (0.27 ± 0.17 N vs 0.18 ± 0.18 N; P = 0.009) (Fig. 5, Table 3). Figure 4: Open in new tabDownload slide Representative figure of coupled recordings of cyclic contractile forces of 8 segments of the annuloplasty ring. Each trace corresponds to 1 mattress suture. Figure 4: Open in new tabDownload slide Representative figure of coupled recordings of cyclic contractile forces of 8 segments of the annuloplasty ring. Each trace corresponds to 1 mattress suture. Figure 5: Open in new tabDownload slide The cyclic contractile forces (CCF) in (A) each segment, (B) each annular area and (C) the commissural area at 3 levels (30 mmHg, 50 mmHg and 70 mmHg) of RVP. Linear mixed-effects models demonstrated that the CCFs were significantly different between segments (P < 0.001). There was no significant difference in changes of the CCF according to the RVPs (P = 0.07). The CCFs of each annular area were significantly different (P = 0.002). The CCF and CCF increases according to the changes in peak RVP were significantly higher at the 3 commissural areas (segments 3, 5 and 8) than the other segments (P = 0.009). Analysis of variance plots reported 95% confidence intervals of the influence of each suture position on CCFs. RVP: right ventricular pressure. Figure 5: Open in new tabDownload slide The cyclic contractile forces (CCF) in (A) each segment, (B) each annular area and (C) the commissural area at 3 levels (30 mmHg, 50 mmHg and 70 mmHg) of RVP. Linear mixed-effects models demonstrated that the CCFs were significantly different between segments (P < 0.001). There was no significant difference in changes of the CCF according to the RVPs (P = 0.07). The CCFs of each annular area were significantly different (P = 0.002). The CCF and CCF increases according to the changes in peak RVP were significantly higher at the 3 commissural areas (segments 3, 5 and 8) than the other segments (P = 0.009). Analysis of variance plots reported 95% confidence intervals of the influence of each suture position on CCFs. RVP: right ventricular pressure. Table 3: Cyclic contractile force at 3 different levels of peak right ventricular pressure in each segment and 3 annular areas . RVP = 30 mmHg . RVP = 50 mmHg . RVP = 70 mmHg . Total . P-value . Segment 1 0.28 ± 0.30 N 0.32 ± 0.22 N 0.31 ± 0.28 N 0.31 ± 0.25 N <0.001b Segment 2 0.21 ± 0.24 N 0.25 ± 0.25 N 0.23 ± 0.22 N 0.23 ± 0.22 N Segment 3 0.28 ± 0.13 N 0.35 ± 0.12 N 0.46 ± 0.09 N 0.36 ± 0.13 N Segment 4 0.11 ± 0.14 N 0.18 ± 0.18 N 0.06 ± 0.03 N 0.12 ± 0.14 N Segment 5 0.14 ± 0.08 N 0.23 ± 0.11 N 0.32 ± 0.34 N 0.23 ± 0.20 N Segment 6 0.10 ± 0.08 N 0.17 ± 0.15 N 0.16 ± 0.17 N 0.14 ± 0.13 N Segment 7 0.18 ± 0.09 N 0.26 ± 0.10 N 0.25 ± 0.02 N 0.23 ± 0.08 N Segment 8 0.22 ± 0.09 N 0.25 ± 0.11 N 0.31 ± 0.17 N 0.26 ± 0.12 N Septal (segments 1–3) 0.26 ± 0.22 N 0.31 ± 0.20 N 0.34 ± 0.22 N 0.30 ± 0.08 N 0.002c Posterior (segments 4, 5) 0.12 ± 0.11 N 0.21 ± 0.14 N 0.19 ± 0.27 N 0.17 ± 0.09 N Anterior (segments 6–8) 0.16 ± 0.10 N 0.22 ± 0.12 N 0.24 ± 0.15 N 0.21 ± 0.12 N Commissural area (segments 3, 5, 8) 0.21 ± 0.11 N 0.28 ± 0.12 N 0.36 ± 0.22 N 0.27 ± 0.17 N 0.012d Non-commissural area 0.17 ± 0.19 N 0.24 ± 0.18 N 0.20 ± 0.19 N 0.18 ± 0.18 N 0.009e Total 0.19 ± 0.17 N 0.25 ± 0.16 N 0.26 ± 0.21 N . RVP = 30 mmHg . RVP = 50 mmHg . RVP = 70 mmHg . Total . P-value . Segment 1 0.28 ± 0.30 N 0.32 ± 0.22 N 0.31 ± 0.28 N 0.31 ± 0.25 N <0.001b Segment 2 0.21 ± 0.24 N 0.25 ± 0.25 N 0.23 ± 0.22 N 0.23 ± 0.22 N Segment 3 0.28 ± 0.13 N 0.35 ± 0.12 N 0.46 ± 0.09 N 0.36 ± 0.13 N Segment 4 0.11 ± 0.14 N 0.18 ± 0.18 N 0.06 ± 0.03 N 0.12 ± 0.14 N Segment 5 0.14 ± 0.08 N 0.23 ± 0.11 N 0.32 ± 0.34 N 0.23 ± 0.20 N Segment 6 0.10 ± 0.08 N 0.17 ± 0.15 N 0.16 ± 0.17 N 0.14 ± 0.13 N Segment 7 0.18 ± 0.09 N 0.26 ± 0.10 N 0.25 ± 0.02 N 0.23 ± 0.08 N Segment 8 0.22 ± 0.09 N 0.25 ± 0.11 N 0.31 ± 0.17 N 0.26 ± 0.12 N Septal (segments 1–3) 0.26 ± 0.22 N 0.31 ± 0.20 N 0.34 ± 0.22 N 0.30 ± 0.08 N 0.002c Posterior (segments 4, 5) 0.12 ± 0.11 N 0.21 ± 0.14 N 0.19 ± 0.27 N 0.17 ± 0.09 N Anterior (segments 6–8) 0.16 ± 0.10 N 0.22 ± 0.12 N 0.24 ± 0.15 N 0.21 ± 0.12 N Commissural area (segments 3, 5, 8) 0.21 ± 0.11 N 0.28 ± 0.12 N 0.36 ± 0.22 N 0.27 ± 0.17 N 0.012d Non-commissural area 0.17 ± 0.19 N 0.24 ± 0.18 N 0.20 ± 0.19 N 0.18 ± 0.18 N 0.009e Total 0.19 ± 0.17 N 0.25 ± 0.16 N 0.26 ± 0.21 N a Values are presented as mean ± standard deviation. b P-value from overall F test of a segment in an LMM. c P-value from overall F test of annular areas in an LMM. d P-value from overall F test of peak right ventricular pressure in an LMM. e P-value from overall F test for comparison between commissural area versus other segments in an LMM. LMM: linear mixed-effects model; N: newton; RVP: right ventricular pressure. Open in new tab Table 3: Cyclic contractile force at 3 different levels of peak right ventricular pressure in each segment and 3 annular areas . RVP = 30 mmHg . RVP = 50 mmHg . RVP = 70 mmHg . Total . P-value . Segment 1 0.28 ± 0.30 N 0.32 ± 0.22 N 0.31 ± 0.28 N 0.31 ± 0.25 N <0.001b Segment 2 0.21 ± 0.24 N 0.25 ± 0.25 N 0.23 ± 0.22 N 0.23 ± 0.22 N Segment 3 0.28 ± 0.13 N 0.35 ± 0.12 N 0.46 ± 0.09 N 0.36 ± 0.13 N Segment 4 0.11 ± 0.14 N 0.18 ± 0.18 N 0.06 ± 0.03 N 0.12 ± 0.14 N Segment 5 0.14 ± 0.08 N 0.23 ± 0.11 N 0.32 ± 0.34 N 0.23 ± 0.20 N Segment 6 0.10 ± 0.08 N 0.17 ± 0.15 N 0.16 ± 0.17 N 0.14 ± 0.13 N Segment 7 0.18 ± 0.09 N 0.26 ± 0.10 N 0.25 ± 0.02 N 0.23 ± 0.08 N Segment 8 0.22 ± 0.09 N 0.25 ± 0.11 N 0.31 ± 0.17 N 0.26 ± 0.12 N Septal (segments 1–3) 0.26 ± 0.22 N 0.31 ± 0.20 N 0.34 ± 0.22 N 0.30 ± 0.08 N 0.002c Posterior (segments 4, 5) 0.12 ± 0.11 N 0.21 ± 0.14 N 0.19 ± 0.27 N 0.17 ± 0.09 N Anterior (segments 6–8) 0.16 ± 0.10 N 0.22 ± 0.12 N 0.24 ± 0.15 N 0.21 ± 0.12 N Commissural area (segments 3, 5, 8) 0.21 ± 0.11 N 0.28 ± 0.12 N 0.36 ± 0.22 N 0.27 ± 0.17 N 0.012d Non-commissural area 0.17 ± 0.19 N 0.24 ± 0.18 N 0.20 ± 0.19 N 0.18 ± 0.18 N 0.009e Total 0.19 ± 0.17 N 0.25 ± 0.16 N 0.26 ± 0.21 N . RVP = 30 mmHg . RVP = 50 mmHg . RVP = 70 mmHg . Total . P-value . Segment 1 0.28 ± 0.30 N 0.32 ± 0.22 N 0.31 ± 0.28 N 0.31 ± 0.25 N <0.001b Segment 2 0.21 ± 0.24 N 0.25 ± 0.25 N 0.23 ± 0.22 N 0.23 ± 0.22 N Segment 3 0.28 ± 0.13 N 0.35 ± 0.12 N 0.46 ± 0.09 N 0.36 ± 0.13 N Segment 4 0.11 ± 0.14 N 0.18 ± 0.18 N 0.06 ± 0.03 N 0.12 ± 0.14 N Segment 5 0.14 ± 0.08 N 0.23 ± 0.11 N 0.32 ± 0.34 N 0.23 ± 0.20 N Segment 6 0.10 ± 0.08 N 0.17 ± 0.15 N 0.16 ± 0.17 N 0.14 ± 0.13 N Segment 7 0.18 ± 0.09 N 0.26 ± 0.10 N 0.25 ± 0.02 N 0.23 ± 0.08 N Segment 8 0.22 ± 0.09 N 0.25 ± 0.11 N 0.31 ± 0.17 N 0.26 ± 0.12 N Septal (segments 1–3) 0.26 ± 0.22 N 0.31 ± 0.20 N 0.34 ± 0.22 N 0.30 ± 0.08 N 0.002c Posterior (segments 4, 5) 0.12 ± 0.11 N 0.21 ± 0.14 N 0.19 ± 0.27 N 0.17 ± 0.09 N Anterior (segments 6–8) 0.16 ± 0.10 N 0.22 ± 0.12 N 0.24 ± 0.15 N 0.21 ± 0.12 N Commissural area (segments 3, 5, 8) 0.21 ± 0.11 N 0.28 ± 0.12 N 0.36 ± 0.22 N 0.27 ± 0.17 N 0.012d Non-commissural area 0.17 ± 0.19 N 0.24 ± 0.18 N 0.20 ± 0.19 N 0.18 ± 0.18 N 0.009e Total 0.19 ± 0.17 N 0.25 ± 0.16 N 0.26 ± 0.21 N a Values are presented as mean ± standard deviation. b P-value from overall F test of a segment in an LMM. c P-value from overall F test of annular areas in an LMM. d P-value from overall F test of peak right ventricular pressure in an LMM. e P-value from overall F test for comparison between commissural area versus other segments in an LMM. LMM: linear mixed-effects model; N: newton; RVP: right ventricular pressure. Open in new tab In addition, increased CCFs according to peak RVP changes were statistically significant only in the commissural segments (segments 3, 5 and 8; P = 0.012) (Fig. 5, Table 3). DISCUSSION This study demonstrated 3 main findings. First, the suture tie-down force at the septal annular area was significantly higher than those at the posterior and anterior annular areas. Second, the CCF was lowest at the posterior annular area and highest at the septal area. Third, the CCF was significantly higher in 3 commissural areas than those in the other segments with significantly increased CCF according to the increased peak RVP. Various suture plication techniques and prosthetic TAP rings have been developed for the treatment of TR. The TAP rings have their own characteristics including hardness of the material and circumferential proportions in the tricuspid annulus. The design of the MC3 annuloplasty ring evaluated in this study was based on that of a 3D-shaped tricuspid annulus of a healthy heart and made as a rigid ring covering the annulus between the anteroseptal commissure to the mid-septal portion [11]. Previous studies have shown favourable results after TAP using this 3D ring [5, 8, 9]. Although the risk of dehiscence is still a concern when using the 3D rigid ring, objective data on this topic are limited. A previous study reported that early ring dehiscence causing severe TR occurred in 8 of 307 patients who received a rigid ring, and all of them were found in the septal annulus [10]. However, another study analysing the holding strength of the suture with a pullout test in 15 ovine tricuspid annular tissues showed that the suture holding strength of the septal portion of the tricuspid annulus was greater than that of the other parts [12]. In this study, down-sized ring annuloplasty was performed to mimic the daily practice for the treatment of functional TR, and CCFs were measured in various RVPs. There are various invasive or non-invasive parameters to access right ventricular (RV) function, including RV peak systolic pressure [13]. However, there is no satisfactory parameter to show exact RV function because of RV anatomical morphology. Therefore, we assumed that CCF measurements at various RVPs using inotropic infusion and injection can represent the situation created by the different contractility forces of the right ventricle. The average suture tie-down force of 4.34 N was higher than the values reported in a previous study that measured suture tie-down forces during mitral ring annuloplasty (2.9 N and 2.2 N for each surgeon), whereas the average CCF of 0.26 N at 70 mmHg RVP was lower than that after mitral annuloplasty (2.0 N) [14]. Individual surgeon variation might exist when tying down the sutures. However, in this study, suturing and knot-tying were performed by a single surgeon who was unaware of the purpose of measuring the tie-down forces during TAP, which was found to be significantly higher in the septal annulus than that in other parts. CCFs were also higher in the septal area than those in the other annular parts. These findings agreed with those from a previous study that showed that suture dehiscence occurred exclusively in the septal annulus after a rigid-ring TAP [10]. Therefore, careful annular suturing and knot-tying might be needed, particularly in the septal annular segments, to prevent cut-through and early dehiscence of the ring when using a rigid TAP ring. In addition, this study showed that CCFs were greater at the commissural segments than at the leaflet midpoints. When considering the findings in a previous study [12] in ex vivo ovine pullout tests showing that the holding strength of the suture was weaker at the commissures than that at leaflet midpoints, suturing the commissural area should be carefully performed to prevent suture dehiscence in the commissural area. Limitations The present study some limitations. First, this study included healthy adult sheep, and the characteristics of the tricuspid annulus might be different from those of a human heart with functional TR. Second, the number of study animals was relatively small even though this study demonstrated statistically significant findings. Third, intraoperative echocardiographic evaluation was not performed, and the RV condition was controlled based on RV pressure rather than on RV function. Although weaning from cardiopulmonary bypass was successful in all the animals, and inotropic agents were used to maintain peak RV pressure, exact left ventricular and RV size and function could not be presented. Fourth, the ring was inserted in an arrested heart, which is a daily routine in our institution. However, our practice may differ from the practices of other institutions, and transient RV dysfunction after cardioplegic arrest could affect the study results. CONCLUSIONS The risk of suture dehiscence after a down-sized 3D rigid-ring TAP might be low because absolute forces remained low in all annular positions, even in high RVP conditions. However, careful suturing is warranted at the septal annular area and commissures to prevent annular tear after the down-sized 3D rigid-ring TAP. SUPPLEMENTARY MATERIAL Supplementary material is available at EJCTS online. ACKNOWLEDGEMENTS The statistical analyses were supported by the Seoul National University Hospital Medical Research Collaborating Center. Funding This work was supported by the Research Affairs of SNU/SNU R&DB Foundation (899–20180451). This work was supported by Research Resettlement Fund for the new faculty of Seoul National University. Conflict of interest: none declared. Author contributions Jae Hong Lim: Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Supervision; Writing—original draft. Heean Shin: Data curation; Formal analysis; Investigation; Supervision; Writing—original draft. Dong Ah Shin: Conceptualization; Data curation; Validation. Dae Hyun Kim: Investigation. Suk Ho Sohn: Conceptualization; Validation. Sungkyu Cho: Conceptualization; Validation. Jae Woong Choi: Conceptualization; Validation. Hee Chan Kim: Conceptualization; Validation. Ho Young Hwang: Conceptualization; Project administration; Validation; Writing—review & editing. Reviewer information European Journal of Cardio-Thoracic Surgery thanks Roman Gottardi and the other, anonymous reviewer(s) for their contribution to the peer review process of this article. REFERENCES 1 Tang GH David TE Singh SK Maganti MD Armstrong S Borger MA. Tricuspid valve repair with an annuloplasty ring results in improved long-term outcomes . Circulation 2006 ; 114 : I577 – 81 . Google Scholar Crossref Search ADS PubMed WorldCat 2 Guenther T Mazzitelli D Noebauer C Hettich I Tassani-Prell P Voss B et al. Tricuspid valve repair: is ring annuloplasty superior? Eur J Cardiothorac Surg 2013 ; 43 : 58 – 65 ; discussion 65. Google Scholar Crossref Search ADS PubMed WorldCat 3 Parolari A Barili F Pilozzi A Pacini D. Ring or suture annuloplasty for tricuspid regurgitation? A meta-analysis review . Ann Thorac Surg 2014 ; 98 : 2255 – 63 . Google Scholar Crossref Search ADS PubMed WorldCat 4 Izutani H Nakamura T Kawachi K. 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Suture dehiscence in the tricuspid annulus: an ex vivo analysis of tissue strength and composition . Ann Thorac Surg 2017 ; 104 : 820 – 6 . Google Scholar Crossref Search ADS PubMed WorldCat 13 Sanz J Sánchez-Quintana D Bossone E Bogaard HJ Naeije R. Anatomy, function, and dysfunction of the right ventricle: JACC state-of-the-art review . J Am Coll Cardiol 2019 ; 73 : 1463 – 82 . Google Scholar Crossref Search ADS PubMed WorldCat 14 Pierce EL Bloodworth CH 4th Siefert AW Easley TF Takayama T Kawamura T et al. Mitral annuloplasty ring suture forces: impact of surgeon, ring, and use conditions . J Thorac Cardiovasc Surg 2018 ; 155 : 131 – 39.e3 . Google Scholar Crossref Search ADS PubMed WorldCat Abbreviations Abbreviations 3D 3-dimensional CCF Cyclic contractile force LMM Linear mixed-effects model RV Right ventricle RVP Right ventricular pressure TAP Tricuspid valve annuloplasty TR Tricuspid regurgitation Author notes †These authors contributed equally to this work. Presented at the 34th Annual Meeting of the European Association for Cardio-Thoracic Surgery, Barcelona, Spain, 8–10 October 2020. © The Author(s) 2021. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Suture tie-down forces and cyclic contractile forces after an undersized tricuspid annuloplasty using a 3-dimensional rigid ring in an ovine model
JF - European Journal of Cardio-Thoracic Surgery
DO - 10.1093/ejcts/ezab131
DA - 2021-03-31
UR - https://www.deepdyve.com/lp/oxford-university-press/suture-tie-down-forces-and-cyclic-contractile-forces-after-an-8Ltrw3p2t1
SP - 1
EP - 1
VL - Advance Article
IS - 
DP - DeepDyve
ER -