A percutaneous approach to create tricuspid regurgitation in swine: a model for transcatheter tricuspid valve therapy assessment.

PURPOSE: The purpose of this study was to develop a simple and effective percutaneous approach to create tricuspid regurgitation in swine. METHODS: Eleven pigs (71.68 ± 7.70 kg, 3 male) were involved in this study. A grasping forceps was introduced into the right ventricle through a steerable sheath under fluoroscopic guidance and used to disrupt the tricuspid valve apparatus by avulsing leaflet or chordae tendineae repeatedly. Transthoracic echocardiography and right ventricular angiography were used to evaluate the degree of tricuspid regurgitation created. RESULTS: Ten of the 11 pigs (90.91%) achieved severe tricuspid regurgitation and 1 (9.09%) obtained moderate tricuspid regurgitation immediately after the procedure. Heart rate of the pigs significantly increased immediately after tricuspid regurgitation creation compared to baseline (88.64 ± 23.24 vs. 76.00 ± 15.30 bpm, P = 0.02), but recovered to normal level at one month follow-up (77.09 ± 11.97 bpm, P = 0.85). The right atrium, tricuspid valve annulus, and right ventricle dilated obviously one month after tricuspid regurgitation creation (dimension changes: 3.01 ± 0.35 vs. 3.56 ± 0.40 cm, P = 0.02; 2.92 ± 0.36 vs. 3.37 ± 0.39 cm, P = 0.01; 3.06 ± 0.42 vs. 3.60 ± 0.47 cm, P = 0.03 respectively). Autopsy findings showed that rupture of leaflet and/or chordae tendineae finally led to the tricuspid regurgitation. CONCLUSIONS: Severe tricuspid regurgitation can be created by a simple and effective percutaneous approach with a grasping forceps in swine model and right heart dilation can be observed consistently at one-month follow-up. This model will be valuable in pre-clinical studies for developing new tricuspid valve repair or replacement technique to treat severe tricuspid regurgitation.

Mitral Valve Posterior Leaflet Reconstruction Using Extracellular Matrix: In Vitro Evaluation.

PURPOSE: To investigate the anatomical and functional effects of complete surgical reconstruction of the posterior mitral leaflet and associated chordae tendineae with a patch made of 2-ply small intestinal submucosal extracellular matrix in vitro. METHODS: Seven explanted mitral valves with intact subvalvular apparatus from 80-kg pigs were evaluated in a left heart simulator and served as their own controls. After testing the native valve, the mitral posterior leaflet and associated chordae tendineae were excised and reconstructed by using the 2-ply small intestinal submucosa extracellular matrix patch. The characterization of the reconstruction was based on geometric data from digital images, papillary muscle force, annular tethering force and leaflet pressure force. RESULTS: The reconstructed valves were fully functional without regurgitation, tearing or rupture during incrementally increased pressure from 0 to 120 mmHg. The leaflet areas were preserved after reconstruction, with a normal configuration of the coaptation line. However, the coaptation midpoint moved posteriorly after reconstruction (A2: 15.8 ± 1.4 vs. 18.9 ± 1.5 mm, p = 0.002, diff = 3.1 mm, 95% CI 1.3 to 4.8 mm). The anterior papillary muscle force increased significantly (3.9 vs. 4.6 N, p = 0.029, diff = 0.7 N, 95% CI 0.1 to 1.4 N at 120mmHg) after reconstruction. The posterior papillary muscle force, leaflet pressure force and annular pressure force did not change significantly. CONCLUSIONS: In this in vitro model, mitral valve anatomy and function were comparable between the native mitral valve and our new surgical technique for complete reconstruction of the posterior mitral leaflet and associated chordae tendineae. These promising results warrant further in vivo evaluation.

Long-term outcomes of chordal replacement with expanded polytetrafluoroethylene sutures to repair mitral leaflet prolapse.

OBJECTIVES: This study examines the durability of mitral valve (MV) repair for mitral regurgitation using chordal replacement with expanded polytetrafluoroethylene sutures to correct leaflet prolapse. METHODS: Isolated chordal replacement was used to correct prolapse in 186 (24.9%) patients and combined with leaflet resection in 560 (75.1%). Patients were followed prospectively with periodical clinical and echocardiographic assessments for a median follow-up of 11 years (range, 7-16 years). RESULTS: Patients' median age was 58 years (range, 48-67 years) and 516 (69.2%) were men. Bileaflet prolapse was present in 63% of patients and advanced myxomatous degeneration was present in 32%. The number of neochords per repaired valve increased over time and was not associated with MV reoperation or recurrent mitral regurgitation. The cumulative incidence of MV reoperation with death as a competing risk was 4.2% (95% confidence interval [CI], 2.4-6.0) at 20 years. Multivariable analysis revealed that previous cardiac operations (hazard ratio, 5.70; 95% CI, 1.96-16.53; P = .001), and isolated anterior leaflet prolapse (hazard ratio, 3.92; 95% CI, 1.106-13.91; P = .034) were associated with increased hazard of MV reoperation. The probability of recurrent moderate or severe mitral regurgitation using repeated measures regression models was 14.1% (95% CI, 10.3-19.0) at 20 years. Variables associated with recurrent MR in multivariable regression analysis were left ventricular ejection <40% (hazard ratio, 3.57; 95% CI, 1.37-9.32; P = .009) and preoperative complete heart block (hazard ratio, 5.90; 95% CI, 2.47-14.09; P < .001). CONCLUSIONS: Chordal replacement with expanded polytetrafluoroethylene sutures provides stable MV function in most patients during the first 2 decades of follow-up.

The effect of chordae tendineae on systolic flow.

When using Computational Fluid Dynamics to simulate ventricular blood flow in the heart, it has been common practice to neglect the effect of the sub-valvular apparatus and the trabeculae on the flow conditions. In this study, we analyze the effect of neglecting the chordae tendineae on the fluid flow and pressure drop. To test the assumption we use a previously developed dynamic 3D model of the left ventricle, aorta and valves that is based on 3D echocardiographic recordings. To this model we add the chordae tendineae as a sub-grid model. The previously developed 3D model for the left ventricle during systole is based on real-time three-dimensional echocardiography (RT3DE) recordings of a 30 years old female volunteer. The segmented ventricular wall does not include details of the aorta and the mitral valve, so these were reconstructed. The subgrid model for the flow across the chordae tendineae is based on the Actuator Line Method, which means that they are represented by drag coefficients. The analysis shows that the effect of the chordae tendineae on the pressure drop and work efficiency of the normal heart during systole is minor, and it seems that for simulating ventricular fluid flow and pressure drop during systole, one can follow the current practice and ignore the chordae. However, there can be local effects such as small vortices behind the chordae. Whether such effects are important for a particular application must be evaluated for the given case.

Identification of Human Pathological Mitral Chordae Tendineae Using Polarization-sensitive Optical Coherence Tomography.

Defects of the mitral valve complex imply heart malfunction. The chordae tendineae (CTs) are tendinous strands connecting the mitral and tricuspid valve leaflets to the papillary muscles. These CTs are composed of organized, wavy collagen bundles, making them a strongly birefringent material. Disorder of the collagen structure due to different diseases (rheumatic, degenerative) implies the loss or reduction of tissue birefringence able to be characterized with Polarization Sensitive Optical Coherence Tomography (PS-OCT). PS-OCT is used to discriminate healthy from diseased chords, as the latter must be excised and replaced in clinical conventional interventions. PS-OCT allows to quantify birefringence reduction in human CTs affected by degenerative and rheumatic pathologies. This tissue optical property is proposed as a diagnostic marker for the identification of degradation of tendinous chords to guide intraoperative mitral valve surgery.

Entire mitral valve reconstruction using porcine extracellular matrix: static in vitro evaluation.

OBJECTIVES: To investigate the feasibility of reconstruction of the entire mitral valve using a tube graft made of 2-ply small intestinal submucosa extracellular matrix in vitro. METHODS: Seven explanted mitral valves with intact subvalvular apparatus from 80 kg pigs were evaluated in a left heart simulator and served as controls. After testing the native valve, the leaflets and chordae tendineae were explanted, and the 2-ply small intestinal submucosa extracellular matrix (CorMatrix®; Cardiovascular Inc., Alpharetta, GA, USA) tube graft was implanted. The characterization was based on geometric data from digital images, papillary muscle force, annular tethering force and leaflet pressure force. RESULTS: The tube grafts were fully functional without any signs of leakage, tearing or rupture during incrementally increased pressures from 0 mmHg to 120 mmHg. The posterior leaflet moved anteriorly and became larger after reconstruction when compared with the native valve. However, the mid coaptation point was preserved. The anterior papillary muscle force decreased significantly (5.2 N vs 4.4 N, P = 0.022 at 120 mmHg), and the posterior papillary muscle force increased significantly (4.8 N vs 5.6 N, P = 0.017 at 120 mmHg) after reconstruction. CONCLUSIONS: The entire mitral valvular and subvalvular reconstruction with a 2-ply small intestinal submucosa extracellular matrix tube graft is feasible in an in vitro model. Our method of reconstruction increased the convexity of the anterior leaflet's coaptation line and significantly redistributed the papillary muscle force towards the posterior papillary muscle. These promising results and the prospect of the entire mitral valvular and subvalvular reconstruction warrant further in vivo evaluations.

Measuring chordae tension during transapical neochordae implantation: Toward understanding objective consequences of mitral valve repair.

OBJECTIVES: Complex structure of mitral valve and its central position in the heart limit assessment of mitral function to standardized calculated parameters assessed using medical imaging (echocardiography). Novel techniques, which allow mitral valve repair (MVr) in a beating heart, offer the opportunity for innovative objective assessment in physiologic and pathologic conditions. We report, to our knowledge, the first data of real-time chordal tension measurement during a transapical neochordae implantation. METHODS: Seven patients with severe degenerative mitral regurgitation due to posterior prolapse underwent transapical MVr using the NeoChord DS 1000 (NeoChord Inc, Minneapolis, Minn). During prolapse correction, the tension applied on the neochordae was measured in addition to hemodynamic and echocardiographic parameters. RESULTS: The traction applied on 1 chorda sustaining the P2 segment was measured at between 0.7 and 0.9 N, and oscillated with respiration. When several neochordae were set in tension, this initial tension was spread homogeneously on each chorda (mean sum of the amplitude of tension 0.98 ± 0.08 N). To achieve an optimal echocardiographic correction, a complementary synchronous traction on all chordae was required. During this adjustment, the sum of the tension decreased (mean 12 ± 2%; P = .018), suggesting that when normal physiology was restored, the valvular apparatus was in a low-stress state. This method allowed us to apply a precise and reproducible technique, leading to a good procedural success rate with a low morbidity and mortality rate. CONCLUSIONS: The tension applied on chordae during transapical implantation of neochordae for degenerative mitral regurgitation can be measured, providing original data about the objective consequences of MVr on the mitral apparatus.

Mitral Chordae Rupture as a Possible First-Time Presentation for Graves’ Disease.

Graves' disease is a common cause of hyperthyroidism that can lead to multiple cardiovascular complications. Herein is described the case of a 44-year-old male who presented with new-onset atrial fibrillation and mitral regurgitation secondary to flail anterior mitral leaflet with chordae tendineae rupture. This is a rare complication for Graves' disease, and has been reported only twice previously. It was hypothesized that this complication is secondary to Graves'-associated myxomatous degeneration of the mitral valve in the presence of a hyperdynamic circulation.

Dilation of tricuspid valve annulus immediately after rupture of chordae tendineae in ex-vivo porcine hearts.

PURPOSE: Chordae rupture is one of the main lesions observed in traumatic heart events that might lead to severe tricuspid valve (TV) regurgitation. TV regurgitation following chordae rupture is often well tolerated with few or no symptoms for most patients. However, early repair of the TV is of great importance, as it might prevent further exacerbation of the regurgitation due to remodeling responses. To understand how TV regurgitation develops following this acute event, we investigated the changes on TV geometry, mechanics, and function of ex-vivo porcine hearts following chordae rupture. METHODS: Sonomicrometry techniques were employed in an ex-vivo heart apparatus to identify how the annulus geometry alters throughout the cardiac cycle after chordae rupture, leading to the development of TV regurgitation. RESULTS: We observed that the TV annulus significantly dilated (~9% in area) immediately after chordae rupture. The annulus area and circumference ranged from 11.4 ± 2.8 to 13.3 ± 2.9 cm2 and from 12.5 ± 1.5 to 13.5 ± 1.3 cm, respectively, during the cardiac cycle for the intact heart. After chordae rupture, the annulus area and circumference were larger and ranged from 12.3 ± 3.0 to 14.4 ± 2.9 cm2 and from 13.0 ± 1.5 to 14.0 ± 1.2 cm, respectively. CONCLUSIONS: In our ex-vivo study, we showed for the first time that the TV annulus dilates immediately after chordae rupture. Consequently, secondary TV regurgitation may be developed because of such changes in the annulus geometry. In addition, the TV leaflet and the right ventricle myocardium are subjected to a different mechanical environment, potentially causing further negative remodeling responses and exacerbating the detrimental outcomes of chordae rupture.

The Adaptive Remodeling of the Anterior Mitral Leaflet and Chordae Tendineae Is Associated with Mitral Valve Function in Advanced Ischemic and Nonischemic Dilated Cardiomyopathy.

The degree or nature of functional mitral regurgitation (MR) is not necessarily correlated with the size or function of the left ventricle (LV). We hypothesized that the anatomical structure of the mitral valve (MV) complex might play a role in functional MR in ischemic or nonischemic dilated cardiomyopathy (DCM).The structure of the LV and MV complex in DCM patients (n = 29) was assessed using electrocardiogram-gated 320-slice computed tomography and was compared with that in healthy patients (n = 12). Twenty-five DCM patients with mild or low MR (DCM-lowMR) had markedly greater length, diameter, and sphericity index of the LV and a larger tenting area than the controls. The distance between the papillary muscle (PM) tip and the mitral annular plane was not different between DCM-lowMR and normal hearts despite the greater LV length observed in DCM-lowMR. Furthermore, DCM-lowMR had markedly longer chordae tendineae (DCM-lowMR: 24 [20-26] mm; controls: 14 [13-16] mm; P < 0.01) and larger anterior leaflets (DCM-lowMR: 30 [27-31] mm; controls: 22 [20-24] mm; P < 0.01), thus suggesting the adaptive remodeling of the MV complex. Four DCM patients with moderate-severe MR had unbalanced remodeling, such as excessive LV dilatation, short anterior mitral leaflets, and short chordae tendineae.The development of functional MR might be associated with the remodeling of LV and MV components, such as the PMs, chordae tendineae, or anterior MV leaflets. Detailed anatomical assessments of the LV and MV complex would contribute to the adequate staging of ischemic or nonischemic DCM.

Politetrafluorene suture used as artificial mitral chord: mechanical properties and surgical implications.

BACKGROUND: Novel surgical approach to repair degenerative mitral regurgitation such as transapical chordae tendineae replacement and "loop in loop" in loop techniques, need of artificial chordae longer than that used in the older techniques of chordae tendineae replacement. This difference in length has been reported as potential critical point for durability of artificial chordae. In the present paper we have investigated the elastic behavior of different diameter and length politetrafluorene (PTFE) suture threads as substitute of native chordae, to identify their reliability to use as long artificial chordae. METHODS: PTFE suture threads with different diameters were investigated in their mechanical properties at different length from 2 to 14 cm, by a servo hydraulic testing machine, to test the elastic properties of the sample in their use as mitral chordae substitutes. RESULTS: Our study shows that the chordae length is an important parameter that can change the performance of chordae itself. The analysis of elastic/properties of suture threads specimen, reveals that long PTFE chords have an optimal mechanical behavior in which elongation is accompanied by a safe elastic properties that make them well resistance during multiple tractions. CONCLUSIONS: In conclusion the use of PTFE as an artificial chordae may represent a valid choice in case of insertion of artificial chordae with extra anatomic length.

Assessment of Mitral Valve Repair With Exercise Echocardiography: Artificial Chordae vs Leaflet Resection.

Mitral valve (MV) repair with artificial chordae (AC) or leaflet resection (LR) is associated with good hemodynamics at rest. The aim of this study was to compare these techniques in terms of exercise capacity and echocardiographic parameters of hemodynamics at rest and peak exercise. We conducted a study in 2015 of 56 patients, who had undergone surgery for degenerative posterior mitral leaflet prolapse between 2005 and 2014 using either AC (n = 24) or LR (n = 32). Clinical data were collected, exercise capacity was measured, and resting echocardiography and peak exercise echocardiography were performed. No significant differences were detected among groups regarding exercise duration or peak exercise workload measured in Watts (W) (AC: 136 ± 43 W and LR: 131 ± 40 W; P = 0.65). The mean mitral gradient at rest was 3.0 ± 1.3 mm Hg in the AC group and 3.0 ± 1.0 mm Hg in the LR group (P = 0.90). The mean MV gradients at peak exercise did not differ significantly between groups (AC: 8.3 ± 3.4 and LR: 11.3 ± 8.7; P = 0.19). Four patients (17%) in the AC group and 1 (3%) in the LR group had systolic anterior motion, P = 0.15. We conclude that both methods of posterior MV leaflet repair were associated with good hemodynamics at rest and peak exercise. The groups had comparable exercise capacity. MV pressure gradients at rest and peak exercise were similar in both groups.