Artificial chordae for degenerative mitral valve disease: critical analysis of current techniques

Mitral Valve Repair of the Anterior Leaflet: Are We There Yet?

Mitral regurgitation is one of the most prevalent valvulopathies with a disease burden that incurs significant healthcare costs globally. Surgical repair of the posterior mitral valve leaflet is a standard treatment, but approaches for repairing the anterior mitral valve leaflet are not widely established. Since anterior leaflet involvement is less common and more difficult to repair, fewer studies have investigated its natural history and treatment options. In this review, we discuss surgical techniques for repairing the anterior leaflet and their outcomes, including survival, reoperation, and recurrence of regurgitation. We show that most patients with mitral regurgitation from the anterior leaflet can be repaired with good outcomes if performed at centers with expertise. Additionally, equal consideration for early repair should be given to patients with mitral regurgitation from both anterior and posterior pathology. However, more studies to better evaluate the efficacy and safety of anterior mitral valve leaflet repair are needed.

Comparison between Track Technique and Conventional Approach for Measuring Artificial Chordae in the Treatment of Anterior Leaflet Prolapse and Flail during Mitral Valve Repair

Background

Measuring the chordae tendineae for mitral valve reconstruction is feasible with various techniques. However, the effect of different strategies on the durability of plastics at follow-up is unknown. The study aims to compare a conventional surgical technique for measuring artificial chordae length with our new approach, defined "track technique".

Methods

We compared the results of patients with anterior leaflet prolapse/flail who underwent mitral valve reconstruction by implanting artificial chordae from January 2020 to January 2022; 22 patients were operated on with a conventional technique, and 25 with our new alternative, "track technique". Clinical and transesophageal echocardiography data were collected postoperatively and at 2 years of follow-up. The primary outcome was freedom from mitral regurgitation. Secondary outcomes were presentation with New York Heart Association (NYHA) class < 2 and leaflet coaptation length ≥ 10 mm.

Results

The patients of the 2 groups had comparable preoperative risk factors regarding the LogEuroSCORE (p = 0.33). Moreover, no difference was observed in terms of the mechanism of mitral valve insufficiency. No hospital or follow-up deaths were recorded for either group. At discharge, no echocardiographic differences were observed in the regarding degree of residual mitral regurgitation, but the measurement of coaptation length was in favor of the alternative group (8.6 ± 1.8 vs. 11 ± 1.4; p = 0.04). At 2 years of follow-up (25 ± 9; range 13-37), the NYHA class was not different; however, the number of patients with 1-2+ recurrent mitral regurgitation was significantly higher in the conventional group (8 vs. 4 patients; p = 0.02), and the coaptation length was in favor of the alternative group (8.8 ± 1.7 vs. 11 ± 1.7; p = 0.04).

Conclusions

We devised both techniques to prove effective in achieving good valvular continence, but a significantly greater coaptation length was obtained with our track technique at the 2 years follow-up.

A review of the development of interventional devices for mitral valve repair with the implantation of artificial chords

Mitral regurgitation (MR) was the most common heart valve disease. Surgical repair with artificial chordal replacement had become one of the standard treatments for mitral regurgitation. Expanded polytetrafluoroethylene (ePTFE) was currently the most commonly used artificial chordae material due to its unique physicochemical and biocompatible properties. Interventional artificial chordal implantation techniques had emerged as an alternative treatment option for physicians and patients in treating mitral regurgitation. Using either a transapical or a transcatheter approach with interventional devices, a chordal replacement could be performed transcatheter in the beating heart without cardiopulmonary bypass, and the acute effect on the resolution of mitral regurgitation could be monitored in real-time by transesophageal echo imaging during the procedure. Despite the in vitro durability of the expanded polytetrafluoroethylene material, artificial chordal rupture occasionally occurred. In this article, we reviewed the development and therapeutic results of interventional devices for chordal implantation and discuss the possible clinical factors responsible for the rupture of the artificial chordal material.

Mitral valve repair with artificial chords: Tips and tricks

Mitral valve regurgitation (MR) is a common valvular disorder occurring in up to 10% of the general population. Mitral valve reconstructive strategies may address any of the components, annulus, leaflets, and chords, involved in the valvular competence. The classical repair technique involves the resection of the prolapsing tissue. Chordal replacement was introduced already in the '60, but in the mid '80, some surgeons started to use expanded polytetrafluoroethylene (ePTFE) Gore-Tex sutures. In the last years, artificial chords have been used also using transcatheter approach such as NeoChord DS 1000 (Neochord) and Harpoon TSD-5. The first step is to achieve a good exposure of the papillary muscles that before approaching the implant of the artificial chords. Then, the chords are attached to the papillary muscle, with or without the use of supportive pledgets. The techniques to correctly implant artificial chords are many and might vary considerably from one center to another, but they can be summarized into three big families of suturing techniques: single, running or loop. Regardless of how to anchor to the mitral leaflet, the real challenge that many surgeons have taken on, giving rise to some very creative solutions, has been to establish an adequate length of the chords. It can be established based on anatomically healthy chords, but it is important to bear in mind that surgeons work on the mitral valve when the heart is arrested in diastole, so this length could fail to replicate the required length in the full, beating heart. Hence, some surgeons suggested techniques to overcome this problem. Herein, we aimed to describe the current use of artificial chords in real-world surgery, summarizing all the tips and tricks.

Biomechanical characteristics of different methods of neo-chordal fixation to the papillary muscles

BACKGROUND AND AIM OF THE STUDY

Several techniques have been described for neo-chordal fixation to the papillary muscles without any reported clinical differences. The objective of this study is to compare in vitro the biomechanical properties of four of these common techniques.

METHODS

We studied the biomechanical properties of expanded polytetrafluoroethylene neo-chordal fixation using four techniques: nonknotted simple stitch, nonknotted figure-of-eight stitch, knotted pledgeted mattress stitch, and knotted pledgeted stitch using commercially available prefabricated loops. Neo-chordae were submitted to a total of 20 traction-relaxation cycles with incremental loads of 1, 2, and 4 N. We calculated the elongation, the force-strain curve, elasticity, and the maximum tolerated load before neo-chordal failure.

RESULTS

The elongation of the neo-chordae was lowest in the simple stitch followed by the figure-of-eight, the pledgeted mattress, and he commercially prefabricated loops (p < .001). Conversely, the elastic modulus was highest in the simple stitch followed by the figure-of-eight, the pledgeted mattress, and the prefabricated loops (p < .001). The maximum tolerated load was similar with the simple stitch (28.87 N) and with the figure-of-eight stitch (31.39 N) but was significantly lower with the pledgeted mattress stitch (20.51 N) and with the prefabricated loops (7.78 N).

CONCLUSION

In vitro, neo-chordal fixation by nonknotted simple or nonknotted figure-of-eight stitches resulted in less compliance as opposed to the use of knotted pledgeted stitches. Fixation technique seemed to influence neo-chordal biomechanical properties, however, it did not seem to affect the strength of the suture when subjected to loads within physiological ranges.

A new technique to adjust the length of artificial chordae during mitral anterior leaflet repair

BACKGROUND

Length measurement of artificial chordae remains a critical step during mitral valve repair (MVr). The aim of this study is to assess the effectiveness of a new length measuring technique.

METHODS

All consecutive patients with anterior leaflet prolapse/flail who underwent MVr using the described method between January 2020 and January 2022 at our institution were included in the analysis. Clinical and transesophageal echocardiography data were collected postoperatively and at 1-year follow-up. The primary outcome was freedom from mitral regurgitation (MR). Secondary outcomes were presentation with New York Heart Association (NYHA) class <2 and leaflet coaptation length ≥10 mm.

RESULTS

Of 25 patients, 16 (64%) were males. A total of 15 (60%) had isolated anterior leaflet disease, while 10 (40%) had concomitant posterior involvement. Twenty patients with isolated MR (80%) underwent right anterior mini-thoracotomy, while 5 (20%) with associated valvular or coronary disease underwent sternotomy. The median number of chordae implanted was 2 [1-4]. Postrepair intraoperative MR grade was 0 in 23 patients (92%) and 1 in 2 (8%). Thirty-day mortality was 0%. De novo atrial fibrillation was 20%. At follow-up, mortality was 0%. No patients presented with moderate or severe MR. A total of 22 patients (88%) were in NYHA class I, while 3 (12%) in class II. The coaptation length was 11 ± 1 mm.

CONCLUSIONS

The short-term outcomes of the described technique are good with adequate leaflet coaptation in all treated patients. Long-term results are needed to assess the stability and durability of this repair technique.

Simplifying Mitral Valve Repair: A Guide to Neochordae Reconstruction

Mitral valve reconstruction techniques using polytetrafluoroethylene sutures are associated with high repair rates and excellent durability but are dependent on accurate neochordae length estimates. Current strategies to determine the appropriate length of artificial neochordae commonly rely on nonphysiologic saline testing on the arrested heart, with erroneous lengths resulting in residual mitral regurgitation. We present a guide for reproducible and accurate neochordae reconstruction based upon transesophageal echocardiographic measurements, which simplifies mitral repair for most patients with degenerative mitral regurgitation and can be used in conventional or minimally invasive approaches.

Combination of the Modified Loop Technique and De Vega Annuloplasty in Dogs with Mitral Regurgitation

Background: Detailed surgical techniques for treating canine mitral regurgitation have not been previously reported. Method: This case series included six consecutive client-owned dogs with mitral regurgitation. All dogs underwent a combined protocol, including the modified loop technique and De Vega annuloplasty (MODEL surgery), in 2021. Artificial loops covering 80% of the length of the strut chordae tendineae were used for chordal replacement. Mitral annuloplasty was subjectively performed, targeting the circumference of the septal leaflet. Results: The breeds were Chihuahua-mixed breed, Spitz, Pomeranian, Cavalier King Charles Spaniel, and Chihuahua, with average ages and weights of 11.4 ± 2.3 years and 5.49 ± 2.98 kg, respectively. The aortic cross-clamp, pumping, and surgery times were 64.0 ± 7.5 min, 168.5 ± 39.1 min, and 321.0 ± 53.1 min, respectively. After MODEL surgery, left atrial-to-aortic ratios significantly decreased from 2.20 ± 0.18 to 1.26 ± 0.22 (p < 0.01), and left ventricular end-diastolic internal diameter normalized to body weight significantly decreased from 2.03 ± 0.26 to 1.48 ± 0.20 (p < 0.01). In all cases, the clinical signs disappeared or improved significantly. Conclusions: MODEL surgery increased mitral valve coaptation, normalized heart sizes, and significantly improved clinical signs in dogs with mitral regurgitation.

Echocardiographic evaluation of deformity and enlargement of the canine mitral valve annulus associated with myxomatous degenerative mitral valve disease

INTRODUCTION/OBJECTIVES

Quantitative evaluation of the morphology of the mitral valve annulus (MVA) in dogs with myxomatous mitral valve disease (MMVD) may improve the techniques of mitral valve plasty. This study aimed to compare the MVA morphology on echocardiography in normal dogs and dogs with MMVD and to compare the echocardiographic and intraoperative measurements of the MVA in dogs with MMVD.

ANIMALS, MATERIALS AND METHODS

The study population comprised 59 healthy dogs (control group) and 371 dogs with MMVD (MMVD group). The anterior-posterior diameter and transversal diameter (TD) of the MVA and the aortic annulus diameter were measured by echocardiography to calculate the mitral valve flattening ratio, mitral annulus area (MAA), mitral annulus circumference (MAC), contraction ratio of the MAA and aortic annulus area. In the MMVD group, the mitral annulus diameter (MAD) was macroscopically measured during mitral valve plasty. Areas and lengths were divided by the body surface area (BSA) and √BSA, respectively, for comparative analyses.

RESULTS

The systolic and diastolic anterior-posterior diameter/√BSA, transversal diameter/√BSA, MAA/BSA converted to a natural logarithm (Ln(MAA/BSA)), and MAC/√BSA was significantly higher in the MMVD group than the control group, whereas flattening ratio values and contraction ratio of the MAA was significantly lower. Neither the aortic annulus diameter /√BSA nor the Ln(aortic annulus area/BSA) significantly differed between groups. In the MMVD group, diastolic MAC/√BSA and MAA/BSA correlated significantly with the MAD/√BSA.

CONCLUSIONS

The MVA is larger and rounder in dogs with MMVD than controls. Two-dimensional echocardiographic measures of MAA and MAC correlate well with intraoperative measures of MAD.

Unsatisfying mitral valve repair? The "Loop method": a lifebelt to grab

Intra-operative mitral valve repair failure is a common condition in patients with complex myxomatous disease requiring aortic re-clamping and application of a fast and easy surgical technique to correct the residual imperfection. Herein we describe a reproducible method of artificial chord reconstruction which preserves the previous accomplished acts and allows for accurate chordal length measurement basing on the annuloplasty as the reference level.

Preoperative determination of artificial chordae tendineae length by transoesophageal echocardiography in totally endoscopic mitral valve repair

OBJECTIVES

Artificial chordae tendineae are widely used for surgical repair in patients with mitral regurgitation due to floppy mitral valve/mitral valve prolapse. Expanded polytetrafluoroethylene has been used to construct these artificial chordae; however, the determination of the optimal length of the chordae prior to surgery has been an issue. For this reason, such a method was developed and the results of its use are presented.

METHODS

Forty-seven consecutive patients with significant mitral regurgitation due to floppy mitral valve/mitral valve prolapse who underwent totally endoscopic mitral valve surgery were studied. The chordae length was predetermined using transoesophageal echocardiography. The length between the top of the fibrous body of the papillary muscle and the coaptation line of the 2 leaflets of the mitral valve was measured and used to define the length of the chordae to be used for repair. Then under stereoscopic vision, a total endoscopic mitral valve repair was performed.

RESULTS

The predicted mean length of chordal loops was 19.76 ± 0.71 mm (median 20, range 16-28) and the actual mean length of chordal loops used was 19.68 ± 0.74 mm (median 20, range 16-26) demonstrating an excellent correlation between the two (r = 0.959). The mean number of chordae loops used per patient was 5.12 ± 0.62 (median 4, range 2-12). All patients at the time of discharge had no or trivial mitral regurgitation on transoesophageal echocardiography.

CONCLUSIONS

The chordae length used for mitral valve repair can be determined prior to surgery using transoesophageal echocardiography with a high degree of accuracy. Further, total endoscopic repair in this group of patients provides excellent results. For these reasons, it is expected that this method will replace most traditional approaches to cardiac surgeries in the years to come.

Mechanical and morphometric study of mitral valve chordae tendineae and related papillary muscle

The mitral valve (MV) apparatus is a complex mechanical structure including annulus, valve leaflets, papillary muscles (PMs) and connected chordae tendineae. Chordae anchor to the papillary muscles to help the valve open and close properly during one cardiac cycle. It is of paramount importance to understand the functional, mechanical, and microstructural properties of mitral valve chordae and connecting PMs. In particular, little is known about the biomechanical properties of the anterior and posterior papillary muscle and corresponding chords. In this work, we performed uniaxial and biaxial tensile tests on the anterolateral (APM) and posteromedial papillary muscle (PPM), and their respective corresponding chordae tendineae, chordae^APM and chordae^PPM, in porcine hearts. Histology was carried out to link the microstructure and macro-mechanical behavior of the chordae and PMs. Our results demonstrate that chordae^PPM are less in number, but significantly longer and stiffer than chordae^APM. These different biomechanical properties may be partially explained by the higher collagen core ratio and larger collagen fibril density of chordae^PPM_. No significant mechanical or microstructural differences were observed along the circumferential and longitudinal directions of APM and PPM samples. Data measured on chordae and PMs were further fitted with the Ogden and reduced Holzapfel - Ogden strain energy functions, respectively. This study presents the first comparative anatomical, mechanical, and structural dataset of porcine mitral valve chordae and related PMs. Results indicate that a PM based classification of chordae will need to be considered in the analysis of the MV function or planning a surgical treatment, which will also help developing more precise computational models of MV.

Echocardiographic Method to Determine the Length of Neochordae Reconstruction for Mitral Repair

BACKGROUND

We evaluated a novel formula using preoperative transesophageal echocardiographic measurements to determine neochordae length for repair of degenerative mitral regurgitation (MR).

METHODS

The formula is based on measuring the distance from the adjacent papillary head to the intended coaptation zone of the flail/prolapsing leaflet segment and subtracting the redundant leaflet length. Between 2008 and 2017, 264 consecutive patients underwent mitral valve repair (82.2% endoscopic, minimally invasive approach and 17.8% sternotomy) with neochordae loop reconstruction (68.6% posterior, 6.4% anterior, and 25% bileaflet repair). Mean patient age was 63 ± 13.6 years, 73.5% were men, and mean left ventricular ejection fraction was 63.1% ± 6.7%.

RESULTS

Mitral valve repair was successful in 100% of patients, with no patient requiring conversion to replacement. Neochordae length measurement was accurate in 259 patients (98%), with 4 patients requiring conversion to resection and 1 patient requiring longer anterior leaflet neochordae. Median anterior and posterior neochordae lengths were 27 mm (range, 18-32) and 17 mm (range, 9-27), respectively. Intraoperative transesophageal echocardiography demonstrated no or trace residual MR in 254 patients and mild residual MR in 10 patients. In-hospital mortality occurred in 1 patient, and complications included respiratory failure (2.7%) and renal failure (1.8%). At the median follow-up of 12.6 months (interquartile range, 11.1), 98.9% of patients remained free from ≥2+ MR, whereas freedom from reoperation was 100%.

CONCLUSIONS

Preoperative transesophageal echocardiographic measurements can accurately and reproducibly predict the required length of neochordae loop reconstruction for degenerative mitral valve repair with good results. Longer-term follow-up is necessary.

Adjusting the neochords height for better leaflets coaptation following mitral valve repair

Often times, in mitral valve repair techniques, the height of the newly placed Gore-Tex sutures needs correction to achieve better mitral valve leaflet coaptation or to correct systolic anterior motion (SAM). Herein, a less challenging "Hornet" technique to accurately adjust artificial chordal length is described. This technique describes a way to adjust/shorten the Gore-Tex chords, should they need revision. Ideally, this should not be needed, however due to the circumstances for mitral valve repair, this is sometimes necessary. With the annuloplasty band already in place, it is somewhat harder to reinsert new chords and hence, this technique may be beneficial.

ChoRe: A device for trans-catheter chordae tendineae repair

This work focuses on the design of a new device (called ChoRe) to place artificial chords in the mitral valve structure during a trans-catheter procedure. The aim of the device is to restore the correct functionality of the valve and solve mitral valve regurgitation, that is, a common consequence of chordae tendineae rupture. An analysis of the requirements was carried out and used to design and develop a first functional prototype. The resulting device was able to connect artificial chords at the posterior leaflet of the mitral valve and at the apex of the left ventricle, also allowing the control of the artificial chord length. The ChoRe was tested ex-vivo in bovine hearts. The qualitative assessment of the ChoRe focused on the performance of the device and preliminary evaluation of the procedure time. Results demonstrated that the device is able to create a top and bottom fixation in an average time of 3.45 ± 1.44 min. Future improvements will focus on enhancing the connection at the leaflet, as well as the overall functionality, in order to guarantee better control of the artificial chord length. This work shows future potentials for more patient-specific treatments in trans-catheter scenarios for mitral valve repair.

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.

Numerical simulation of transapical off-pump mitral valve repair with neochordae implantation

BACKGROUND

Transapical off-pump mitral valve (MV) repair is a novel minimally-invasive surgical technique, allowing to correct mitral regurgitation (MR) caused by chordae tendineae rupture. While numerical simulation of the MV structure has proven to be useful to evaluate the effects of the MV surgical repair techniques, no numerical simulation studies on the outcomes of transapical MV repair have been done up to now.

OBJECTIVE

The purpose of this study is to evaluate the transapical MV repair using finite element modeling and to determine the effect of the neochordal length on the function of the prolapsing MV.

METHODS

The reconstruction of the MV geometry based on the patient-specific data was performed. In order to simulate prolapse, chordae inserted into the middle segment of the posterior leaflet (P2) were ruptured. A total of four virtual transapical repairs using neochordae of different length were performed. The function of the MV before and after virtual repairs was simulated.

RESULTS

The evaluation of the effect of the neochordal length on post-repair MV function showed that the length of the implanted neochordae has a significant impact on the correction of MR caused by chordae tendineae rupture.

CONCLUSIONS

The presented results can improve the understanding of the effects of transapical MV repair.

Initial Experience With a New Mitral Ring Designed to Simplify Length Determination of Neochords

BACKGROUND

Artificial chord implantation has become one of the most applied techniques for mitral valve repair (MVR). Many techniques have been described, with the goal of optimizing neochord implantation. A new annuloplasty device designed to simplify the determination of the appropriate neochord length has been recently introduced. We describe our initial experience with this new device.

METHODS

The semirigid device is equipped with removable loops on the posterior aspect of the ring. Neochords are tied to the loops, which are subsequently removed. The device was implanted in 47 symptomatic patients from January 2015 to August 2016 through a median sternotomy in 33 patients (70.2%) and a right anterolateral minithoracotomy in 14 (29.8%). The cause of mitral valve insufficiency was degenerative in all patients, and most patients presented with isolated prolapse of the posterior leaflet. Before and after cardiopulmonary bypass, all patients underwent evaluation with transesophageal echocardiography, and transthoracic echocardiography was performed at discharge.

RESULTS

A median of 2 neochords were implanted (minimum, 1; maximum, 6). Mean cardiopulmonary bypass time and aortic cross-clamp times were 141.7 ± 32.3 and 104.8 ± 28.5 minutes for combined and 133 ± 53.9 and 98.3 ± 41.6 minutes for isolated MVR. At discharge, echocardiography revealed no or only mild mitral insufficiency in 45 patients (mean gradient, 2.9 ± 1.3 mm Hg).

CONCLUSIONS

This new annuloplasty ring facilitated determination of appropriate neochord length and was used to successfully treat different degenerative pathologies affecting both leaflets. This new device simplified length determination of the neochords.

Use of a New Expanded Polytetrafluoroethylene Multichordal Mitral Apparatus (MitraPatch) to Repair Complex Mitral Valve Lesions

OBJECTIVE

We report a new expanded polytetrafluoroethylene multichordal mitral apparatus (MitraPatch) to simplify mitral repairs involving multiple cusps and sought to describe the surgical technique and demonstrate the efficacy of the device.

METHODS

MitraPatch was laser cut from a single sheet of expanded polytetrafluoroethylene and mounted on a custom-designed handle. Surgical technique to deploy the apparatus on the native mitral valve was developed in ex vivo porcine hearts. Hemodynamic efficacy of repairing mitral prolapse and regurgitation was assessed in ex vivo hearts and in five 30-day chronic swine, with histopathology in an additional swine at 120 days after implantation.

RESULTS

In ex vivo heart studies, leaflet coaptation was restored from 0 mm at the posterior prolapsing segment to 8.1 ± 2.2 mm after repair with the MitraPatch (P < 0.05) and to 10.2 ± 1.3 mm after the repair of the anterior leaflet (P < 0.05). In in vivo studies, valve function at 30 days was considered good, with none to trace regurgitation. Device was flexible, without tissue overgrowth or dehiscence. At 120 days, complete endothelialization was observed.

CONCLUSIONS

The multichordal MitraPatch can potentially simplify complex mitral valve repairs involving multiple leaflet cusps, possibly enabling an optimal mitral repair even by surgeons without the focused high-volume experience.

How to Adjust Neochordae Length Accurately in Degenerative Mitral Regurgitation

We describe a simple technique for the accurate adjustment of polytetrafluoroethylene neochordae length in degenerative mitral regurgitation using the annuloplasty ring's own suture as a reference instead of using sophisticated or less precise maneuvers. Two threads of the annuloplasty ring suture are placed at the level of the mitral valve annulus plane to be used as a reference to tie the neochordae.

An Automated Expanded Polytetrafluoroethylene Suturing and Coaxial Fastener System for Mitral Chordae Replacement: Strength, Feasibility, and Healing

OBJECTIVE

Mitral valve (MV) chordae replacements can be technically challenging. Technology that remotely delivers and accurately secures artificial chordae may reduce the learning curve and improve the reliability of MV repairs.

METHODS

The technology involved two devices: a remote suturing device for delivery of expanded polytetrafluoroethylene (ePTFE) suture to the papillary muscle and a Coaxial titanium suture fastener (TF) device with integrated saline infusion for real-time determination of chordae length during fixation. A mechanical model simulating MV chordae tension in a beating heart quantified the durability of 120 coaxially fastened ePTFE sutures using TF over time. Investigation of the technology was performed in ex vivo porcine, ovine, and in situ cadaver hearts, whereas live-tissue testing was conducted in a survivor ovine model. Mitral valve repair procedures involved the iatrogenic induction of mitral regurgitation by the resection of one to two native MV chordae, followed by implantation of ePTFE suture using the technology. Epicardial echocardiography, saline infusion testing, and histologic analysis evaluated MV competence, repair integrity, and long-term healing.

RESULTS

Durability testing of ePTFE suture secured with TF demonstrated no degradation of TF pull-apart forces of for 440 million cycles. Mitral valve repairs using the technology were performed in eight sheep; four demonstrating proof of concept and four survived for an average of 6.5 months after completion of the procedure. At reoperation, echocardiography demonstrated trace to no mitral regurgitation with near complete endothelialization of the TF and artificial chordae.

CONCLUSIONS

This technology successfully enabled the implantation of artificial chordae while providing real-time adjustment of chordae length during MV repair. These results encourage further investigation of its use clinically.

Mitral Valve Chordae Tendineae: Topological and Geometrical Characterization

Mitral valve (MV) closure depends upon the proper function of each component of the valve apparatus, which includes the annulus, leaflets, and chordae tendineae (CT). Geometry plays a major role in MV mechanics and thus highly impacts the accuracy of computational models simulating MV function and repair. While the physiological geometry of the leaflets and annulus have been previously investigated, little effort has been made to quantitatively and objectively describe CT geometry. The CT constitute a fibrous tendon-like structure projecting from the papillary muscles (PMs) to the leaflets, thereby evenly distributing the loads placed on the MV during closure. Because CT play a major role in determining the shape and stress state of the MV as a whole, their geometry must be well characterized. In the present work, a novel and comprehensive investigation of MV CT geometry was performed to more fully quantify CT anatomy. In vitro micro-tomography 3D images of ovine MVs were acquired, segmented, then analyzed using a curve-skeleton transform. The resulting data was used to construct B-spline geometric representations of the CT structures, enriched with a continuous field of cross-sectional area (CSA) data. Next, Reeb graph models were developed to analyze overall topological patterns, along with dimensional attributes such as segment lengths, 3D orientations, and CSA. Reeb graph results revealed that the topology of ovine MV CT followed a full binary tree structure. Moreover, individual chords are mostly planar geometries that together form a 3D load-bearing support for the MV leaflets. We further demonstrated that, unlike flow-based branching patterns, while individual CT branches became thinner as they propagated further away from the PM heads towards the leaflets, the total CSA almost doubled. Overall, our findings indicate a certain level of regularity in structure, and suggest that population-based MV CT geometric models can be generated to improve current MV repair procedures.

Tissue-engineered mitral valve chordae tendineae: Biomechanical and biological characterization of decellularized porcine chordae

Chordae tendineae are essential for maintaining mitral valve function. Chordae replacement is one of the valve repair procedures commonly used to treat mitral valve regurgitation. But current chordae alternatives (polytetrafluoroethylene, ePTFE) do not have the elastic and self-regenerative properties. Moreover, the ePTFE sutures sometimes fail due to degeneration, calcification and rupture. Tissue-engineered chordae tendineae may overcome these problems. The utility of xenogeneic chordae for tissue-engineered chordae tendineae has not yet been adequately explored. In this study, polyelectrolyte multilayers (PEM) film modified decellularized porcine mitral valve chordae (PEM-DPC) were developed to explore tissue-engineered chordae tendineae as neochordae substitutes. Fresh porcine mitral chordae were decellularized and reserved the major elastic fiber and collagen components. Decellularized chordae with a PEM film were produced with chitosan-heparin by a lay-by-lay technique. Mesenchymal stem cells and vascular endothelial cells could grow well on the surface of the PEM-DPC. The superior biomechanical properties of PEM-DPC were proved with good flexibility and strength both in vitro and in vivo. PEM-DPC can be developed for potential alternative mitral valve chordae graft.

A new method for the adjustment of neochordal length: the adjustable slip knot technique

The use of expanded polytetrafluoroethylene (ePTFE) sutures for the correction of mitral valve prolapse has become a standardized procedure. Adjustment of neochordal length is crucial to the efficacy of this technique. Various methods have been described for this purpose; however, the fine adjustment of neochordal length is technically challenging. We describe a simple and effective technique for the implantation of neochordae, which we have termed the 'adjustable slip knot technique'. The first step of this technique is reinforcement of the papillary muscle by a Teflon pledget with or without polytetrafluoroethylene (CV-4) loops. The second step is the formation of a neochordal loop by introducing an ePTFE suture between the affected mitral leaflet and the papillary muscle or ePTFE loops. The third step is the adjustment of the length of neochordae. The formation of a slip knot in one arm of the ePTFE suture is the pivot of this technique. The neochordal loop can be constricted by the application of tension to one arm of the suture. We applied this technique in 5 patients with satisfactory results.

Chordae replacement versus leaflet resection in minimally invasive mitral valve repair

For many years, the quadrangular resection technique first proposed by Carpentier has become the gold standard for repair of posterior leaflet prolapse of the mitral valve (MV). Although this "resection" technique and its modifications are safe and very effective, they do not respect the anatomy of the MV and the physiological role of the posterior leaflet. Therefore some new techniques, aiming to preserve MV leaflets to a different extent, have been proposed. With the use of expanded polytetrafluoroethylene (ePTFE), neochordae leaflet preserving techniques for posterior MV prolapse treatment have emerged. The aim of these techniques is to support the free edge of the prolapsing segments and thereby restore the physiologic function of the MV. A simplified modification of this technique using premeasured ePTFE loops ("loop technique") was successfully introduced to ease the implantation of neochordae, especially in the setting of minimally invasive MV surgery. While "resection" techniques are associated with excellent long-term results, there is evolving evidence in favor of "non-resection" techniques supporting the concept of a "respect rather than resect" approach.

Real-time three-dimensional transesophageal echocardiography to predict artificial chordae length for mitral valve repair

Background

Artificial chordae replacement is an effective technique for mitral valve repair, however, it is difficult to accurately determine the length of artificial chordae. This study aimed to assess the reliability and accuracy of real-time three-dimensional transesophageal echocardiography (TEE) to predict the length of artificial chordae preoperatively.

Methods

From December 2008 to December 2010, 48 patients with severe mitral regurgitation successfully underwent mitral valve repair using artificial chordae replacement. The patients were divided into a TEE pre-measurement group (n = 26) and a direct measurement group (n = 22), according to the method used to determine the length of artificial chordae. Cardiopulmonary bypass time, aortic cross-clamp time, and the recurrence rate of moderate or severe mitral regurgitation were compared between the two groups.

Results

There were no operative deaths in either group. The mean cardiopulmonary bypass time was 113.0 ± 18.7 min and 127.0 ± 28.9 min (p < 0.05), and the aortic cross-clamp time was 70.0 ± 16.6 min and 86.0 ± 20.7 min (p < 0.05) in the TEE pre-measurement group and direct measurement group, respectively. The difference between the pre-measured artificial chordal length and actual constructed artificial chordal length was not significant in the TEE pre-measurement group (p > 0.05). Although the difference in the incidence of moderate or severe mitral regurgitation between the two groups was not significant (p > 0.05), the incidence in the TEE pre-measurement group (3.8%) was lower than that in the direct measurement group (18.2%).

Conclusions

Real-time three-dimensional transesophageal echocardiography can accurately predict the length of artificial chordae required for mitral valve repair, and shortens cardiopulmonary bypass time and aortic cross-clamp time while improving the results of mitral valve repair.