Pathologic aspects of polytetrafluoroethylene sutures in human heart

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.

Artificial chordae for mitral valve repair

BACKGROUND

Mitral valve repair using expanded polytetrafluoroethylene sutures to replace mitral chordae tendineae is a well-established procedure. However, the incidence of neo-chordae failure causing recurrent mitral regurgitation is not well defined.

METHODS

We have reviewed the reported cases of complications after mitral valve repair related to the use of neo-chordae. This study was mainly carried out through PubMed, Medline, and Google Chrome websites.

RESULTS

We have identified a total of 26 patients presenting with rupture of polytetrafluoroethylene neo-chordae, mostly being described as isolated cases. Few other cases of recurrent mitral regurgitation with hemolysis were found, where reoperation was not caused by neo-chordal failure but most likely by technical errors. At pathological investigation the findings were substantially similar in all reported cases. The neo-chordae retained their length and pliability, became covered with host tissue and rupture was mainly related to suture size. Mild calcification was observed not interfering with chordal function; chordal infection did never occur.

CONCLUSIONS

The use of artificial neo-chordae provides excellent late results with durable mitral valve repair stability. Chordal rupture may occur late postoperatively leading to reoperation because of recurrent mitral regurgitation. Despite its rarity, this potential complication should not be overlooked during follow-up of patients after mitral valve repair using artificial neo-chordae.

Mid-Term Follow-Up of Neonatal Neochordal Reconstruction of Tricuspid Valve for Perinatal Chordal Rupture Causing Severe Tricuspid Valve Regurgitation

BACKGROUND

Papillary muscle rupture in the perinatal period is a rare event that leads to severe mitral or tricuspid insufficiency due to a flail leaflet. Neonatal tricuspid chordal reconstruction for this condition is rarely reported. Early recognition and treatment have the potential to be lifesaving. We present our surgical experience with five such patients, along with their midterm follow-up.

METHODS

Between August 2010 and November 2012, five neonates (aged 1-30 days) underwent surgery for severe atrioventricular valve regurgitation. All neonates had severe tricuspid regurgitation due to ruptured chordae. In addition, two had moderate mitral regurgitation; one due to ruptured chordae of the posterior mitral leaflet and the other due to prolapse of the anterior mitral leaflet. All underwent emergent surgery where the ruptured chordae to the anterior tricuspid leaflet were replaced with neochordae made with expanded polytetrafluoroethylene (ePTFE) suture. The mitral valve was repaired in two patients.

RESULTS

All patients survived surgery without the need for postoperative mechanical circulatory assist. Predischarge echocardiograms showed good coaptation of tricuspid and mitral leaflets with minimal regurgitation in all. At follow-up between 75 months to 102 months, four patients had excellent outcomes with less than mild tricuspid regurgitation. One child with flail tricuspid and mitral leaflets developed progressive tricuspid and mitral regurgitation requiring surgical re-repair at 20 months following the initial surgery.

CONCLUSION

Repair of chordal rupture of the tricuspid valve in neonates using ePTFE neo-chordae can provide acute salvage and gratifying midterm results in the management of this potentially fatal condition.

Chordal Replacement with Polytetrafluoroethylene Suture: Midterm Results

From March 1994 to December 1999, polytetrafluoroethylene suture was used for chordal replacement during mitral valve repair in 30 patients. Follow-up ranged from 4 to 70 months with a mean of 36.6 months and was complete in 29 patients: 14 males and 15 females with a mean age of 40.6 years. Most (17) had rheumatic heart disease, 5 had degenerative disease, 6 had infective endocarditis, and 1 had ischemic heart disease. Preoperatively, 26 patients were in functional class III and IV. Operations comprised isolated mitral valve repair (15), combined mitral and tricuspid valve repair (4), mitral valve repair and aortic valve replacement (3), and others (7). The most frequent additional procedures were commissurotomy, papillotomy, resection of primary or secondary chordae, and chordal splitting. The mean cardiopulmonary bypass and aortic crossclamp times were 155.3 and 120.5 minutes, respectively. There was no hospital mortality. One patient died 20 months postoperatively from chronic obstructive lung disease. All survivors were in functional class I and II. Mitral regurgitation was reduced from a preoperative mean of +3.1 degrees to +0.43 degrees. No thromboembolic event or valve failure occurred during follow-up. It was concluded that polytetrafluoroethylene suture was safe and effective for mitral valve repair.

Chordal Replacement with Expanded Polytetrafluoroethylene Suture: Early Results

Expanded polytetrafluoroethylene suture has been used for chordal replacement to achieve better results of mitral valve repair in patients with severe subvalvular disease. From March 1994 to December 1996, 16 patients with mitral valve disease were successfully repaired with this suture at Central Chest Hospital. There were 10 males and 6 females. The average age was 36.5 years. Mean follow-up was 18.18 months. Mitral valve disease was rheumatic in origin in most patients. The suture was attached to the posterior leaflet in 11 patients and to the anterior leaflet in the other 5. The average number of pairs of sutures used per patient was 1.37 (range 1 to 4 pairs). The average number of surgical procedures for mitral valve repair per patient was 5.1. There was no hospital mortality and no thromboembolic complication or reoperation during this study. Postoperative functional status and mitral regurgitation improved substantially. We concluded from this study that this suture can be used safely and effectively for chordal replacement in mitral valve repair.

Loop technique for mitral valve repair

A new artificial chordal reconstruction technique has been developed using several expanded polytetrafluoroethylene (ePTFE) loops. This technique differs from conventional artificial chordal reconstruction in the use of premeasured ePTFE loops. The loop technique involves several steps: (1) assessment of the corresponding papillary muscle; (2) measurement of the required ePTFE loop length; (3) making a loop set of the premeasured length; (4) anchoring the loop set to the papillary muscle; (5) fixing the ePTFE loops to the prolapsing leaflet; (6) adjusting the loop length if necessary; and (7) ring implantation. Favorable early and mid-term results of this loop technique have been reported in patients undergoing mitral valve repair through mini-thoracotomy and via median sternotomy, with 3-year survival and re-operation-free rates of 94.8 and 97.4 %, respectively. The loop technique using ePTFE chordal reconstruction with premeasured loops thus appears to be a safe, reliable, and reproducible technique for mitral valve repair. In addition, it is suitable for both minimally invasive and conventional sternotomy approaches, and represents a useful technique for treating posterior, anterior, and especially bi-leaflet prolapses.

A 17-year experience with mitral valve repair with artificial chordae in infants and children

OBJECTIVES

We sought to examine our long-term results of mitral valve (MV) repair with expanded polytetrafluoroethylene (ePTFE) sutures and to determine the predictors for the outcome of this procedure.

METHODS

Between 1995 and 2011, MV repair with chordal reconstruction by artificial chordae was achieved in 78 patients (34 males and 44 females). Median age at repair was 1.5 years (range 3.6 months-13.4) and weight was 9.1 kg (2.5-31.4). The mean follow-up was 8.3 years. A Cox proportional hazards model was used to analyse the risk factors for a composite outcome of death, conversion to other MV repair techniques or MV replacement, reoperation on MV and recurrent mitral regurgitation (MR).

RESULTS

According to Carpentier classification, 65 (83.3%) patients were Type 2 and 13 (16.7%) were Type 3. Mitral annuloplasty was performed in all cases, except 2. During MV repair, 8 (10.3%) patients were ineffective with artificial chordae and converted to other techniques. Six (7.7%) patients underwent MV reoperation (three repairs and three replacements). Freedom from MV reoperation was 92.5 and 90.4% at 5 and 10 years, respectively. There was 1 in-hospital death. At the latest follow-up, moderate or more MR was observed in 3 (3.8%) patients. Risks for the composite outcome were low body weight at operation and Carpentier classification Type 3.

CONCLUSIONS

MV repair with artificial chordae in infants and children is safe and effective and associated with a low reoperation rate. Further investigation into the long-term durability and biological adaptation of ePTFE sutures after patient growth is mandatory.

Post-mortem evaluation of expanded polytetrafluoroethylene (ePTFE) used in mitral valve repair in dogs

Mitral valve repair is one of the treatment options for mitral regurgitation. Expanded polytetrafluoroethylene (ePTFE) is a polymer that has been widely used in cardiovascular surgery. In this case series, we report the autopsy and histological findings in 6 dogs that underwent cardiopulmonary bypass for mitral annuloplasty using ePTFE sheets and chordoplasty using ePTFE sutures. From May 2005 to October 2009, 3 female and 3 male dogs with severe mitral regurgitation underwent mitral valve repair. This case series included 3 Cavalier King Charles spaniels, 2 Maltese, and 1 Shih Tzu. The survival period after surgery was 19-72 (35 ± 19) months. In all the cases, autopsy revealed that the ePTFE sheets and sutures were not damaged and well integrated into the surrounding highly differentiated, connective tissues. Low-power microscopy revealed that in all cases, the tissues surrounding the ePTFE sheet in the mitral valve annulus had almost completely been covered by granulation tissue. No inflammatory infiltrate or thrombogenesis was observed around the ePTFE in any of the cases. There was no evidence of reactive changes in the region surrounding the ePTFE. These results suggest that ePTFE has excellent tissue compatibility and durability and can be effectively used for canine mitral valve repair.

Seven years’ experience with suture annuloplasty for mitral valve repair

OBJECTIVE

Our early experience with the mural annulus shortening suture procedure for mitral valve repair showed superior hemodynamic performance over ring annuloplasty. The aim of this study was to assess the durability of the mural annulus shortening suture procedure and evaluate our 7-year experience regarding valve function, hemodynamic performance, and clinical outcome.

METHODS

Between 1996 and 2003, 222 elective consecutive patients (58.1% males; age, 59 +/- 14 years) underwent simple or complex mitral valve repair. Minimal invasive reconstruction was performed in 150 patients. For correction of annular dilatation, we used double-running 2-0 polytetrafluoroethylene sutures to reinforce the posterior circumference of the annulus. Patients were investigated prospectively by means of transthoracic echocardiography before discharge and 1 and 5 years after the operation. The mean follow up was 32 +/- 21 months (range 1-77 months).

RESULTS

The operative mortality was 3.1%. Hemodynamic performance at 1 and 5 years showed low mean transvalvular gradients (2.1 +/- 0.9 and 2.0 +/- 0.8 mm Hg, respectively) and a calculated mitral valve orifice area of 3.3 +/- 0.9 cm2 and 3.1 +/- 0.6 cm2, respectively, with progressive annular dilatation from 31.2 +/- 3 mm to 33.9 +/- 4 mm at 1 year and 35.7 +/- 4 mm at 5 years (P < .01). Clinical status improved from New York Heart Association class 3.0 +/- 0.4 to 0.6 +/- 0.8 at 1 year and 0.8 +/- 0.8 at 5 years. Freedom form nontrivial residual mitral regurgitation was 82.3%, freedom from reoperation was 95.1% and actuarial survival was 87.2%, all at 77 months.

CONCLUSIONS

The midterm results show satisfactory hemodynamic performance and clinical improvement. Valve competence and reoperation rates are comparable with those of other reports. Durability of the mural annulus shortening suture procedure for mitral valve repair is questioned because progressive annular redilatation occurs.

Structural Characterization of the Chordae Tendineae in Native Porcine Mitral Valves

BACKGROUND

This study was aimed to characterize the different mitral valve chordae tendineae to provide additional understanding of their function.

METHODS

Mitral valve chordae tendineae from fresh porcine hearts were stained for collagen and elastin using either a Verhoeff and van Gieson stain or Verhoeff light green stain. Cellular distribution was determined using a hematoxylin and eosin stain. Immunohistochemistry was used to verify the findings of vasculature. Biochemical assays were performed to quantify DNA, collagen, and elastin content of each of the six different types of chordae tendineae.

RESULTS

Blood vessels were observed in the longitudinal and circumferential directions of the chordae. The strut chordae on the anterior leaflet of the mitral valve showed an increased degree of vascularization compared with the other chordae. All chordae had an inner layer characterized by a high concentration of collagen and an outer layer that was mostly elastin with interwoven collagen fibers. The collagen microstructure was characterized by directional crimping. Hematoxylin and eosin staining showed fibroblasts evenly distributed throughout the inner and outer layer of the chordae tendineae. Quantitative analysis showed significantly higher levels of DNA and collagen content in the anterior and posterior marginal chordae compared with the other chordae.

CONCLUSIONS

The chordae tendineae were seen to have different microstructures according to chordal type. The presence of vessels characterized the chordae tendineae as complex living components that work in coordination with the papillary muscles and mitral valve leaflets to prevent mitral valve prolapse and regurgitation. They may also function to supply nutrients to the valve leaflets.

Late results of mitral valve repair for mitral regurgitation

OBJECTIVE

This study was undertaken to evaluate the long-term results of mitral valve repair for mitral regurgitation.

METHODS

Between 1991 and 2000, 301 patients with mitral regurgitation underwent mitral valve repair. There were 167 men and 134 women whose mean age was 56 +/- 14 years. The patients were comprised of 7 patients in Carpentier's type I, 277 patients in type II, and 17 patients in type III. Chordal replacement with expanded polytetrafluoroethylene sutures had been prospectively applied to repair the anterior mitral leaflet prolapse. Ring annuloplasty was performed in 230 patients (76%). The follow-up was complete and mean follow-up was 67 +/- 33 months, for a cumulative follow-up of 1,624 patient-years.

RESULTS

There were 5 hospital deaths and 11 late deaths (2 cardiac and 9 noncardiac). All survivors except those with stroke were in the New York Heart Association (NYHA) functional class I or II. At 10 years, the actuarial survival was 90 +/- 3%, the freedom from embolism was 86 +/- 4%, the freedom from reoperation was 96 +/- 2%, and the freedom from valve-related events was 77 +/- 4%. At 10 years, the freedom from reoperation in the patients with anterior leaflet prolapse was 90 +/- 5%.

CONCLUSIONS

Mitral valve repair is feasible in most patients with mitral regurgitation and is associated with low mortality and low rates of valve related events. Chordal replacement with expanded polytetrafluoroethylene sutures is effective, safe, and durable at long-term follow-up for patients with anterior leaflet prolapse.

Mitral-valve repair without annuloplasty rings: results after repair of anterior leaflet versus posterior-leaflet defects using polytetrafluoroethylene sutures for chordal replacement

OBJECTIVE

Defects of the anterior mitral leaflet (AML), including ruptured chordae, are often regarded as difficult or even impossible to repair. Chordal replacement may also be an option in extensive disease of the posterior mitral leaflet (PML). It has not yet been clearly defined whether the repair of either mitral leaflet using chordal-replacement techniques is as safe as the standard repair of the mitral valve (MV) including quadrangular resection and ring reduction alone.

METHODS

Between October 1995 and June 1999, 160 patients underwent MV repair for mitral regurgitation (MR) in our institution. Chordal replacement with polytetrafluoroethylene (PTFE) sutures for elongated or ruptured chordae was performed in 72 (45%) patients. These patients were divided into two groups according to the location of the MV lesions: 48 patients with prolapse of the anterior or both leaflets (AML group) received an average of 2.2+/-1. 1 PTFE sutures for repair; in 24 patients with isolated PML defects (PML group), we used an average of 1.5+/-0.8 PTFE sutures. No prosthetic annuloplasty rings were used. Dilatation of the posterior mitral ring was corrected by PTFE suture annuloplasty. The remaining 88 patients underwent a standard mitral repair without chordal replacement. There were no statistically significant (NS) differences between the two groups (AML/PML) regarding age (59/62 years, P=0.49), left ventricular (LV) ejection fraction (64/66%, P=0. 6) and preoperative NYHA class (2.9/2.9, P=0.36). Postoperatively, all patients were followed by serial transthoracic echocardiography at 1 week and after 3, 6, 12 and 24 months by the same investigator.

RESULTS

In-hospital mortality was 4.2% (2/48) in the AML group and 0% (0/24) in the PML group (P=0.55). Three of the AML patients (6. 3%) and one PML patient (4.2%) underwent reoperation for recurrent MR (P=1.0). The 1- and 2-year freedom from MV reoperation was 95. 1+/-3.4 and 92.6+/-4.2% in the AML group versus 95.0+/-4.9 and 95. 0+/-4.9% (P=0.67). The 1- and 2-year freedom from residual or recurrent MR grade 2 or higher was 97.6+/-2.4 and 94.9+/-3.5% (AML) versus 95.8+/-4.0 and 95.8+/-4.0% (PML) (P=0.97).

CONCLUSIONS

We were unable to find statistically significant differences concerning mortality, freedom from recurrent MR and MV reoperation between the AML and PML groups. Extensive prolapse or chordal pathology of the anterior and PML can be corrected by chordal replacement. Using these techniques, stable repair can be achieved in more than 90% of patients at mid-term follow-up. Long-term observations are necessary to confirm the durability of this type of MV repair.

Repair of congenital tricuspid valve abnormalities with artificial chordae tendineae

BACKGROUND

Congenital abnormalities of the tricuspid valve, including Ebstein's malformation, dysplasia, straddling, and those found in pulmonary atresia with intact septum and congenitally corrected transposition, are an uncommon cause of tricuspid regurgitation. Congenital tricuspid valve anomalies are found as a spectrum of disease in which both the leaflets and the subvalvar apparatus are often involved. Tricuspid valve repair is complicated in such patients because the chordae tendineae are often abnormally short and thick. Replacement or augmentation of chordae tendineae has proved to be a useful component of mitral valve repair. In the present report, we describe the techniques and results of chordal augmentation in the repair of congenital tricuspid valve abnormalities.

METHODS

Since July 1992, tricuspid valve repair has been performed in 5 children with severe tricuspid regurgitation secondary to congenital abnormalities of the tricuspid valve with significant chordal pathology. As a component of the repair, chordal replacement or augmentation was performed using expanded polytetrafluoroethylene suture.

RESULTS

Intraoperative and postoperative echocardiographic assessment showed good mobility of the tricuspid valve leaflets and trivial to mild tricuspid regurgitation. There were no complications and no early or late mortality. At follow-up of 34 to 60 months (median, 49 months), tricuspid valve function has remained excellent in 4 of the 5 patients. In the remaining patient, progressive regurgitation of the right ventricle to pulmonary artery allograft conduit has led to right ventricular dilatation, with a secondary increase in tricuspid regurgitation from trivial to moderate.

CONCLUSIONS

Chordal replacement or augmentation with expanded polytetrafluoroethylene suture is a useful technique in the repair of congenitally dysplastic tricuspid valves with abnormal chordal structures.