Annular and subvalvular dynamics after extracellular matrix mitral tube graft implantation in pigs.

OBJECTIVES: Entire mitral valve reconstruction with an extracellular matrix tube graft is a potential candidate to overcome the current limitations of mechanical and bioprosthetic valves. However, clinical data have raised concern with respect to patch failure. The aim of our study was to evaluate the impact of extracellular matrix mitral tube graft implantation on mitral annular and subvalvular regional dynamics in pigs. METHODS: A modified tube graft design made of 2-ply extracellular matrix was used (CorMatrix®; Cardiovascular Inc., Alpharetta, GA, USA). The reconstructions were performed in an acute 80-kg porcine model (N = 8), where each pig acted as its own control. Haemodynamics were assessed with Mikro-Tip pressure catheters and mitral annular and subvalvular geometry and dynamics with sonomicrometry. RESULTS: Catheter-based peak left atrial pressure and pressure difference across the mitral and aortic valves in the reconstructions were comparable to the values seen in the native mitral valves. Also comparable were maximum mitral annular area (755 ± 100 mm2), maximum septal-lateral distance (29.7 ± 1.7 mm), maximum commissure-commissure distance (35.0 ± 3.4 mm), end-systolic annular height-to-commissural width ratio (10.2 ± 1.0%) and end-diastolic interpapillary muscle distance (27.7 ± 3.3 mm). Systolic expansion of the mitral annulus was, however, observed after reconstruction. CONCLUSIONS: The reconstructed mitral valves were fully functional without regurgitation, obstruction or stenosis. The reconstructed mitral annular and subvalvular geometry and subvalvular dynamics were found in the same range to those in the native mitral valve. A regional annular ballooning effect occurred that might predispose to patch failure. However, the greatest risk was found at the papillary muscle attachments.

Annular Dynamics and Leaflet Geometry in Patch Reconstruction of the Posterior Mitral Leaflet After Adding a Flexible Annuloplasty Ring.

PURPOSE: Patch reconstruction of the posterior mitral leaflet using small intestinal submucosa extracellular matrix has been successfully performed in a porcine study. The patch reconstruction, however, resulted in non-physiological systolic widening of the mitral annulus, suggesting the need for an annuloplasty ring. The objective was to characterize the impact on annular dynamics and leaflet geometry of adding a flexible annuloplasty ring to the posterior mitral leaflet patch reconstruction. METHODS: Measurements were performed in an acute 80-kg porcine model, with seven pigs acting as their own controls. The posterior mitral leaflet was reconstructed with a 2-ply small intestinal submucosa extracellular matrix patch (CorMatrix®). Additionally, a Simulus® Flexible Annuloplasty Ring (Medtronic Inc., Minneapolis, MN, USA) was inserted. Mitral annular dynamics were evaluated using sonomicrometry, and leaflet geometry was described using echocardiography. RESULTS: The annuloplasty ring reduced mitral annular dimensions and restricted cyclic changes in mitral annular area (126 ± 19 vs. 30 ± 13 mm2, p < 0.001), septal-lateral and commisure-commisure distances. Ring annuloplasty prevented systolic widening in the mitral annulus after posterior mitral leaflet reconstruction. The annular saddle shape and leaflet coaptation length (8.7 ± 2.3 vs. 9.7 ± 1.3 mm, p = 0.221) were comparable before and after ring insertion. CONCLUSIONS: The flexible annuloplasty ring resulted in a downsized annulus with restriction of cyclic annular changes in the reconstructed mitral valve. Ring insertion preserved the annular saddle shape and coaptation length. The ring annuloplasty counteracted the non-physiological annular dynamics, and this may improve durability of the posterior mitral leaflet patch reconstruction.

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.

Entire mitral reconstruction with porcine extracellular matrix in an acute porcine model.

OBJECTIVE: The objective of our study was to investigate the feasibility of reconstructing the entire mitral valvular and subvalvular apparatus in pigs using a modified tube graft design made of 2-ply small intestinal submucosa extracellular matrix. METHODS: The reconstructions were performed in an acute 80-kg porcine model with 8 pigs, each acting as its own control. A modified tube graft was designed from a sheet of 2-ply small intestinal submucosa extracellular matrix. Before and after mitral valve reconstruction, echocardiography was used to assess mitral regurgitation, left ventricular outflow tract obstruction due to systolic anterior motion, mitral stenosis, leaflet mobility, and leaflet geometry. RESULTS: The reconstructed mitral valves were fully functional without any observable echocardiographic signs of regurgitation. We did not observe any left ventricular outflow tract obstruction due to systolic anterior motion nor any mitral valve stenosis, despite a diminished septal-lateral distance after reconstruction. The reconstruction had a reduced tenting area, a reduced coaptation length (9.6 ± 1.7 mm vs 7.9 ± 1.0 mm, P = .010, diff = -1.7 mm, 95% confidence interval, -3.1 to -0.4 mm), and atrial bending of both leaflets. CONCLUSIONS: In this acute porcine study, entire mitral valvular and subvalvular apparatus reconstruction using a modified tube graft design made from 2-ply small intestinal submucosal extracellular matrix was feasible. The 2-ply small intestinal submucosa extracellular matrix could withstand the pressure exerted by the left ventricle without any signs of tearing or rupture. These promising results warrant further assessment of both the annular geometry and the long-term durability.

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.

Mitral annuloplasty ring with selective flexibility for septal-lateral contraction and remodelling properties.

OBJECTIVES: To develop and evaluate a novel mitral annuloplasty ring with selective flexibility for septal-lateral contraction and rigidity for septal-lateral dilatation in an acute porcine model. METHODS: The novel mitral annuloplasty ring was designed with slits in the luminal posterior segment and annular lateral segments. The slits were designed to allow inward motion during contraction and to block outward motion during dilation. The novel mitral annuloplasty ring was tested in vitro with a dedicated mechanical test bench, followed by in vivo characterization, using sonomicrometry and echocardiography for annular and leaflet geometry, in an acute porcine model. RESULTS: From the in vitro characterization, we verified that the ring could easily contract (0.7 mm/N) in the septal-lateral dimension, while dilatation was restrained (0.4 mm/N). In vivo characterization showed a cyclic range of 2.8 ± 0.0 mm for septal-lateral contraction. CONCLUSIONS: A novel saddle-shaped remodelling mitral annuloplasty ring was developed with selective flexibility for septal-lateral contraction and rigidity for septal-lateral dilatation. The advantages of this specific ring is that it re-establishes the coaptation plane, ensures leaflet mobility and septal-lateral flexibility and at the same time improves tissue adaptation and thereby decreases the risk of ring dehiscence and redilatation of the mitral annulus. This concept may prove beneficial for patients with ischaemic mitral valve regurgitation or degenerative valve disease.

Biomechanical characterization and comparison of different aortic root surgical techniques.

OBJECTIVES: Understanding the biomechanical impact of aortic valve-sparing techniques is important in an era in which surgical techniques are developing and are increasingly being used based on biomechanical understanding that is essential in the refining of existing techniques. The objective of this study was to describe how the valve-sparing remodelling (Yacoub) and reimplantation (David Type-1) techniques affect the biomechanics of the native aortic root in terms of force distribution and geometrical changes. METHODS: Two force transducers were implanted into 22 pigs, randomized to 1 of 3 groups (David = 7, native = 7 and Yacoub = 8) along with 11 sonomicrometry crystals and 2 pressure catheters. Force and geometry data were combined to obtain the local structural stiffness in different segments of the aortic root. RESULTS: The radial structural stiffness was not different between groups (P = 0.064) at the annular level; however, the David technique seemed to stabilize the aortic annulus more than the Yacoub technique. In the sinotubular junction, the native group was more compliant (P = 0.036) with the right-left coronary segment than the intervention groups. Overall, the native aortic root appeared to be more dynamic at both the annular level and the sinotubular junction than both intervention groups. CONCLUSIONS: In conclusion, the David procedure may stabilize the aortic annulus more than the Yacoub procedure, whereas the leaflet opening area was larger in the latter (P = 0.030). No difference (P = 0.309) was found in valve-opening delay between groups. The 2 interventions show similar characteristics at the sinotubular junction, whereas the David technique seemed more restrictive at the annular level than the Yacoub technique.

In-Vivo Evaluation of Flexible Mitral Annuloplasty Rings: Are They All the Same?

BACKGROUND: Currently, several different flexible mitral annuloplasty rings are available, and their efficacy for surgical repair of the mitral valve is, in general, considered equal. However, clinical experience indicates differences in remodeling capacity that have not yet been quantitatively assessed. The study aim was to compare the biomechanical properties of two commonly used flexible mitral annuloplasty rings in an acute pig model. METHODS: Medtronic Simulus Flex (n = 5) and Medtronic Duran AnCore (n = 7) flexible mitral annuloplasty rings were implanted in pigs (bodyweight 80 kg). The native mitral valve was used as a reference (n = 7). Mitral annular dynamics and dimensions were assessed using 11 sonomicrometry crystals placed in the mitral apparatus. A dedicated force transducer was used to detect deformational force transmission between the annuloplasty ring and the mitral annulus. RESULTS: Cyclic changes in mitral annular circumference and commissure-commissure distance were significantly reduced in the Simulus Flex group compared to the Duran AnCore group (p = 0.025 and p <0.01, respectively). In the Simulus Flex group, smaller deformational forces were recorded compared to the Duran AnCore group, but the difference was not statistically significant (p = 0.52 and p = 0.06 for the septal-lateral and the commissure-commissure force measurements, respectively). CONCLUSIONS: The Simulus Flex ring showed significantly more remodeling capacity than the Duran AnCore ring, but the latter ring preserved the natural dynamics of the mitral valve to a greater degree. Insights into these biomechanical differences may facilitate strategies for surgical reconstruction in degenerative mitral valve disease, especially in patients with excessive amounts of tissue and who are at risk of systolic anterior motion of the mitral valve.

Comparison of the Dacron ring and suture annuloplasty for aortic root repair: an in vitro evaluation.

OBJECTIVES: Increasing evidence shows that annular stabilization is essential in most aortic valve repair procedures. However, a standardized comparison of the 2 commonly used annuloplasty procedures is lacking. We hypothesized that the Dacron ring is more rigid than the polytetrafluoroethylene suture, whereas both procedures decrease annular dimensions. The aim of this study was to compare the biomechanical properties of the ring and suture techniques with native aortic roots in vitro. METHODS: Eighteen aortic roots explanted from 80-kg pigs were randomized into a Dacron ring group, a suture annuloplasty group and a native control group. Each sample was tested in a pulsatile in vitro model with a force transducer attached to the aortic annulus to obtain radial force measurements, and annular dynamics was evaluated using 2-dimensional echography. RESULTS: Among the 2 annuloplasty procedures, only the Dacron ring group provided a significant reduction in the annular diameter compared with the native group (P < 0.006). Both annuloplasty procedures significantly reduced the geometric orifice area, tenting area and sinus diameter while increasing the coaptation length compared with the native group. Systolic annular distension was retained between groups, although the total radial forces were significantly reduced in the procedure groups compared with the native group (ring 1.07 ± 0.45 N, suture 1.13 ± 0.39 N and native 3.55 ± 1.34 N, P < 0.001). CONCLUSIONS: Although both annuloplasty procedures increase coaptation length and decrease geometric orifice area, a significant downsizing of the annulus was achieved using the Dacron ring only. The systolic annular distension was similar to the native aortic root, whereas the radial annular forces were evenly decreased by both annuloplasty procedures. Long-term studies are needed to disclose any difference in long-term effect of the annuloplasty procedures.

Mitral valve posterior leaflet reconstruction using extracellular matrix: an acute porcine study.

OBJECTIVES: To investigate mitral valve posterior leaflet and subvalvular reconstruction using a 2-ply small intestinal submucosal extracellular matrix sheet. METHODS: Mitral valve posterior leaflet and subvalvular reconstruction was characterized in an acute 80-kg porcine model with 7 pigs acting as their own controls. The characterization was based on pressure catheter measurements of pressure differences to identify mitral regurgitation, stenosis and systolic anterior motion. Furthermore, echocardiography was used for the evaluation of leaflet mobility and geometry, whereas sonomicrometry was used to describe annular and subvalvular geometry. RESULTS: The reconstructed mitral valve was fully functional without any signs of regurgitation (peak left atrial pressure for baseline and reconstruction 12 ± 2 mmHg vs 11 ± 2 mmHg, P = 0.550), mitral valve stenosis (mean pressure difference across the mitral valve 4.8 ± 2.3 mmHg vs 4.1 ± 2.3 mmHg, P = 0.589) or systolic anterior motion. The echocardiographic characterization revealed septal-lateral downsizing, reduced tenting area, increased coaptation length (6.0 ± 0.6 mm vs 8.7 ± 2.3 mm, P = 0.002) and an atrial bend of the reconstructed posterior leaflet. A ballooning effect of the patch material was present at the posterior annular segment. CONCLUSIONS: Mitral valve posterior leaflet and subvalvular reconstruction using a 2-ply small intestinal submucosal extracellular matrix sheet as patch material was possible in an acute porcine model. The reconstructed mitral valve was fully functional without signs of mitral valve stenosis, valve regurgitation, stenosis or systolic anterior motion. The ballooning appearance of the patch material might, however, constitute an altered leaflet stress distribution in this area.

Mid-term function and remodeling potential of tissue engineered tricuspid valve: Histology and biomechanics.

OBJECTIVE: Tricuspid valve reconstruction using a small intestinal submucosal porcine extracellular matrix (ECM) tube graft is hypothesized to be durable for six months and show signs of recellularization and growth potential. The purpose was to histologically and biomechanically test ECM valves before and after six months of implantation in pigs for comparison with native valves. METHODS: Ten 60 kg pigs were included, which survived tricuspid valve tube graft insertion. Anterior and septal tricuspid leaflets were explanted from all animals surviving more than one month and examined histologically (n = 9). Endothelialization, collagen content, mineralization, neovascularization, burst strength and tensile strength were determined for native valves (n = 5), ECM before implantation (n = 5), and ECM after six months (n = 5). RESULTS: Collagen density was significantly larger in ECM at implantation (baseline) compared to native leaflet tissue (0.3 ±â€¯0.02 mg/mm3 vs. 0.1 ±â€¯0.03 mg/mm3, p < .0001), but collagen density decreased and reached native leaflet collagen content, six months after ECM implantation (native vs. ECM valve at six months: 0.1 ±â€¯0.03 mg/mm3 vs. 0.2 ±â€¯0.05 mg/mm3, p = .8). Histologically, ECM valves showed endothelialization, host cell infiltration and structural collagen organization together with elastin generation after six months, indicating tissue remodeling and -engineering together with gradual development of a close-to-native leaflet structure without foreign body response. CONCLUSIONS: ECM tricuspid tube grafts were stronger than native leaflet tissue. Histologically, the acellular ECM tube grafts showed evidence of constructive tissue remodeling with endothelialization and connective tissue organization. These findings support the concept of tissue engineering and recellularization, which are prerequisites for growth.

Remodeling Mitral Annuloplasty Ring Concept with Preserved Dynamics of Annular Height.

BACKGROUND AND AIM OF THE STUDY: The configuration of the native annulus changes from nearly flat in the diastolic phase to saddle-shaped in the systolic phase. The present study was conducted to test a novel remodeling annuloplasty ring with built-in septal-lateral fixation and commissural axial flexibility so as to maintain the change in annular saddle shape. The study aim was to evaluate the in-vivo biomechanical performance of the novel annuloplasty ring, compared with the native valve and a semi-rigid and rigid annuloplasty ring. METHODS: All measurements were performed in vivo using a porcine model. A total of 28 pigs (bodyweight ca. 80 kg) were randomized to four groups: (i) with no ring; (ii) with a novel remodeling ring; (iii) with a semi-rigid ring (Physio I Ring, Edwards Lifesciences); and (iv) with a rigid ring (Classic Annuloplasty Ring, Edwards Lifesciences). Force measurements were performed using a dedicated transducer to determine remodeling capacity of the annuloplasty rings. Geometric parameters were measured by implanting sonomicrometry crystals along the mitral annulus. RESULTS: All ring groups significantly restricted the cyclic change of the mitral annulus compared with the 'no-ring' group. The change and maximum value of the annular height were maintained for the novel ring but were significantly decreased for the rigid and semi-rigid rings compared with the 'no-ring' group. Mitral annular force measurements confirmed that the overall remodeling capacity of the novel ring was comparable with the conventional ring groups, and significantly higher in the septal-lateral direction compared to the semi-rigid ring. CONCLUSIONS: In-vivo geometry and force measurements indicated that the intended design features of the new device were successfully provided. The novel ring concept with remodeling properties, combined with the advantages of a flexible annuloplasty ring, is unique. The maintenance of annular saddle shape and cyclic change in annular height may be an important step towards improved mitral valve repair.

Small intestinal submucosa tricuspid valve tube graft shows growth potential, remodelling and physiological valve function in a porcine model†.

OBJECTIVES: Tricuspid valve reconstruction using small intestinal submucosal extracellular matrix (ECM) designed as a tube graft is possible in severe valve pathology. Using cardiac magnetic resonance imaging (MRI) and digital photograph imaging, valves were evaluated after 6 months in a porcine model. METHODS: Ten 60 kg pigs received a tricuspid valve tube graft. A baseline MRI was performed after 2 weeks ( n = 8). A follow-up MRI was performed in three of five 6 months' survivors to assess function and haemodynamics of the tricuspid tube graft. Valves were explanted in five animals for gross examination. No statistical comparisons were made due to low numbers. RESULTS: : Compared to the original tube graft, leaflet area and leaflet height decreased after 6 months (32 ± 0 vs 14.7 ± 4 cm 2 and 3.2 ± 0 vs 1.7 ± 0.3 cm, respectively). Both imaging modalities showed septal dehiscence in all tube grafts after 6 months causing haemodynamically severe paravalvular regurgitation. Cardiac MRI showed a significant remodelling of the right ventricular and annular dimensions. The cardiac output decreased (67 ± 16 vs 34 ± 5 ml/min/kg), while right ventricular stroke volume increased from 64.4 ± 14.6 to 107 ± 63.9 ml. This corresponded to a paravalvular regurgitant volume increasing from 7.2 ± 7.3 to 71.7 ± 69.6 ml. CONCLUSIONS: The ECM tube grafts seemed to remodel over time with loss of redundant ECM material. However, tube graft dehiscence caused severe tricuspid paravalvular regurgitation and heart failure. These data suggest that surgical reinforcement, e.g. adjunct annuloplasty, should be considered to improve durability.

Regional Changes in Leaflet Coaptation Dynamics After Total Tricuspid Reconstruction.

BACKGROUND: Stentless porcine extracellular matrix tricuspid tube grafts were developed for tricuspid valve reconstruction. The purpose of this study was to conduct an echocardiographic assessment of the performance of native and tube graft leaflets in an acute porcine model. METHODS: Fourteen 65-kg pigs were randomly assigned to tube graft (n = 7) or control with native valve preservation (n = 7). Epicardial echocardiography was performed at baseline after sternotomy, after valve operation, and after hemodynamic stabilization. RESULTS: No baseline differences were found (p > 0.05). All valves were competent with only a mild central regurgitant jet in two tube grafts and two native valves. Tube graft valves were compared with native valves. Anterior-septal leaflet coaptation length (18 ± 6 mm versus 6 ± 1 mm, p < 0.0005), coaptation height (20 ± 9 mm versus 9 ± 4 mm, p < 0.005), and anterior leaflet length (31 ± 1 mm versus 22 ± 2 mm, p < 0.00005) were all significantly larger in the tube graft valves. The billowing index (0.8 ± 0.1 versus 0.9 ± 0.1, p > 0.05) and tenting height (5 ± 1 mm versus 4 ± 2 mm, p > 0.1) were not significantly different. Leaflet excursion angles for both leaflets were not significantly different between the native and tube graft valves (p > 0.1). CONCLUSIONS: In a porcine experimental model, a competent tricuspid valve was constructed using extracellular matrix tube graft material. Coaptation geometry was significantly different from native valves with an increased coaptation zone because of excessive leaflet tissue in the tube graft valves. The tube graft tended to prolapse into the atrium, but it did not compromise the motion and competence of the leaflets.

Functional and Biomechanical Performance of Stentless Extracellular Matrix Tricuspid Tube Graft: An Acute Experimental Porcine Evaluation.

BACKGROUND: Stentless porcine extracellular matrix tricuspid tubular valves have been developed for tricuspid valve reconstruction. The purpose of this study was to compare biomechanical and functional performance of native and tube graft valves in an acute porcine model. METHODS: Twenty-two 65-kg pigs were randomized to tube graft or control with native valve preservation. Anterior papillary muscle force was measured with a dedicated force transducer. Microtip pressure catheters were placed in the right atrium and ventricle. Leaflet motion and three-dimensional valve geometry were evaluated using 13 sonomicrometry crystals: six in the tricuspid annulus, one on each leaflet free edge, one on each papillary muscle tip, and one in the right ventricular apex. RESULTS: No regurgitation and no significant differences in intracavitary pressures, annular motion, or leaflet excursion angles were observed after tube graft implantation (p > 0.05). Compared with the native valve, the tricuspid annulus, leaflet orifice area, annular diameters, and the septal segment of the annulus were significantly smaller in the tube graft group (p < 0.05). Maximum anterior papillary muscle force was significantly lower in the tube graft group (p < 0.005). The implantation technique led to an annular circumferential downsizing of 20% ± 17%. CONCLUSIONS: An extracellular matrix tube graft implanted in the tricuspid position produces a competent valve with physiologic performance that, despite downsizing, makes the tube graft an attractive alternative to valve replacement. The downsizing of the implantation should be considered when planning tube graft size and may be potentially beneficial by relieving tension on the repaired tissue, thereby increasing durability.

Simultaneous in- and out-of-plane Mitral Valve Annular Force Measurements.

Mitral valve repair with annuloplasty is often favoured over total valve replacement. In order to develop and optimize new annuloplasty ring designs, it is important to study the complex biomechanical behaviour of the valve annulus and the subvalvular apparatus with simultaneous in- and out-of-plane restraining force measurements. A new flat D-shaped mitral valve annular force transducer was developed. The transducer was mounted with strain gauges to measure strain and calibrated to provide simultaneous restraining forces in- and out of the mitral annular plane. The force transducer was implanted and evaluated in an 80 kg porcine experimental model. Accumulation of out-of-plane restraining forces, creating strain in the anterior segment were 0.7 ± 0.0 N (towards apex) and an average force accumulation of 1.5 ± 0.3 N, creating strain in the commissural segments (away from apex). The accumulations of in-plane restraining forces, creating strain on the inner side of the ring were 1.7 ± 0.2 N (away from ring center). A new mitral annular force transducer was successfully developed and evaluated in vivo. The transducer was able to measure forces simultaneously in different planes. Initial indications point towards overall agreement with previous individual force measurements in- and out-of the mitral annular plane. This can provide more detailed insight into the annular force distribution, and could potentially improve the level of evidence based mitral valve repair and support the development of future mitral annuloplasty devices.

Papillary muscle force distribution after total tricuspid reconstruction using porcine extracellular matrix: in-vitro valve characterization.

BACKGROUND AND AIM OF THE STUDY: The use of extracellular matrix (ECM) from the porcine small intestinal submucosa has shown promising results in reconstructive heart surgery. The study aim was to compare native and ECM tricuspid valves with regards to tricuspid leaflet coaptation geometry and force development in the three papillary muscles, under normal ventricular pressures. METHODS: Six native porcine tricuspid valves and five ECM valves were examined in a static pressure right-heart simulator. Water was used in the ventricular chamber to induce adequate pressure changes (from 5 to 40 mmHg). Dedicated force transducers were used to measure force development in the three papillary muscles in parallel with ventricular pressure measurements. Relative leaflet area was defined as the percentage that one leaflet area comprised of the whole orifice area. The estimated peak leaflet pressure force was defined as leaflet area x peak ventricular pressure, and peak leaflet tethering force was calculated as the average of two adjacent papillary muscles forces. Valve competence and leaflet areas were documented using digital photography. RESULTS: The relative leaflet area of the anterior leaflet was significantly smaller (0.4 versus 0.5, p < 0.01) and that of the posterior leaflet was significantly larger (0.3 versus 0.2; p < 0.001) in ECM tube grafts compared to native valves. No difference was found between septal leaflet relative areas (p > 0.1). Accordingly, estimated peak leaflet pressure forces were greater in anterior leaflets and smaller in the posterior leaflets of native valves compared to ECM valves (p < 0.01). However, peak papillary muscle forces and peak leaflet tethering forces did not differ significantly between the valves. CONCLUSION: A competent and functional tricuspid valve can be constructed in vitro from ECM. In spite of different leaflet area distributions, the force distribution and tethering forces were not significantly different between the two valve types, indicating that a physiologically functioning tricuspid valve can be constructed from ECM.

[Carney complex: a syndrome with cardial, cutaneous and neuronal tumours]. / Carney complex: et syndrom med kardielle, kutane og neuronale tumorer.

A 12 year-old boy presented with neurological symptoms and was found to have a left atrial myxoma. Characteristic facial skin pigmentation raised a suspicion of Carney complex, a rare autosomal dominant disease, which includes cutaneous changes, atrial myxomas and neuroendocrine tumours. The boy's mother had similar skin pigmentation and on subsequent cardiac echocardiography she was found to have left and right atrial myxomas. Both mother and child underwent successful surgical resection of the myxomas.