Expanded polytetrafluoroethylene monocuspid valve for right ventricular outflow tract reconstruction

Application of Biosheets as Right Ventricular Outflow Tract Repair Materials in a Rat Model

Purposes

We report the experimental use of completely autologous biomaterials (Biosheets) made by “in-body tissue architecture” that could resolve problems in artificial materials and autologous pericardium. Here, Biosheets were implanted into full-thickness right ventricular outflow tract defects in a rat model. Their feasibility as a reparative material for cardiac defects was evaluated.

Methods

As the evaluation of mechanical properties of the biosheets, the elastic moduli of the biosheets and RVOT-free walls of rats were examined using a tensile tester. Biosheets and expanded polytetrafluoroethylene sheet were used to repair transmural defects surgically created in the right ventricular outflow tracts of adult rat hearts (n = 9, each patch group). At 4 and 12 weeks after the operation, the hearts were resected and histologically examined.

Results

The strength and elastic moduli of the biosheets were 421.3 ± 140.7 g and 2919 ± 728.9 kPa, respectively, which were significantly higher than those of the native RVOT-free walls (93.5 ± 26.2 g and 778.6 ± 137.7 kPa, respectively; P < 0.005 and P < 0.001, respectively). All patches were successfully implanted into the right ventricular outflow tract-free wall of rats. Dense fibrous adhesions to the sternum on the epicardial surface were also observed in 7 of 9 rats with ePTFE grafts, whereas 2 of 9 rats with biosheets. Histologically, the vascular-constructing cells were infiltrated into Biosheets. The luminal surfaces were completely endothelialized in all groups at each time point. There was also no accumulation of inflammatory cells.

Conclusions

Biosheets can be formed easily and have sufficient strength and good biocompatibility as a patch for right ventricular outflow tract repair in rats. Therefore, Biosheet may be a suitable material for reconstructive surgery of the right ventricular outflow tract.

Right ventricular outflow tract obstruction: a quest for ideal management

Management of right ventricular outflow tract obstruction has undergone much change over the last century. Techniques described in the literature include anatomical repairs and the use of various patches, conduits, and innovative grafts. However, many of these approaches require reoperations or catheter-based interventions, leading to increased morbidity, mortality, and cost. The search for the ideal long-lasting conduit continues and there are new techniques on the horizon, using genetic engineering and nanotechnology. This review discusses the evolution of various techniques for repair of right ventricular outflow tract obstruction, past and current conduits, as well as ongoing research.

Early and 1-year outcome and predictors of adverse outcome following monocusp pulmonary valve reconstruction for patients with tetralogy of Fallot: A prospective observational study

Background and Objectives:

Repair of tetralogy of Fallot (TOF) with monocusp pulmonary valve reconstruction prevents pulmonary regurgitation (PR) for a variable period. Since postoperative outcome is governed by PR and right ventricular function, we sought to assess the severity of pulmonary regurgitation and right ventricular outflow (RVOT) gradient in the immediate postoperative period and at 1 year and attempted to identify the anatomical substrates responsible for adverse outcomes.

Methods:

The study included 30 patients. Transthoracic echocardiography was performed before surgery, within 5 days of surgery, and 1 year later. Presence and severity of PR, RVOT gradient, and residual branch pulmonary stenosis were assessed. Right ventricular and monocusp valve functions were studied.

Results:

Median age was 36.5 months (3-444 months). There were no deaths. Pulmonary regurgitation was mild in 18, moderate in 10, and severe in 2 patients immediately following surgery. At 1 year, 10 patients had severe PR and one had significant RVOT gradient. None of the variables like age, presence of supravalvar pulmonary branch stenosis, main pulmonary artery diameter, or mobility of monocusp valve was found to have any significant association with the progression of PR. McGoon index <1.5 showed a trend toward more PR, while patients with more residual RVOT gradient had lesser regurgitation.

Conclusions:

Repair of TOF with monocusp pulmonary valve reduces immediate postoperative PR. At 1 year, the monocusp valve underwent loss of function in a significant proportion and PR also progressed. This study could not identify any predictors of progression of PR, though patients with McGoon index <1.5 tended to have more PR while those with more outflow gradient had lesser PR.

Prosthetic reconstruction of bicuspid pulmonary valve in tetralogy of Fallot

BACKGROUND

Various techniques have been described for preserving pulmonary valve function in tetralogy of Fallot repair. In selected substrates, the pulmonary valve can be bicuspidized and preserved using polytetrafluoroethylene pericardial membrane.

METHODS

This study was a retrospective review of 20 patients aged 11 months to 31 years with tetralogy of Fallot and a bicuspid pulmonary valve (with anteroposterior cusps) who underwent intracardiac repair from August 2010 to January 2013. The anterior cusp was augmented using polytetrafluoroethylene pericardial membrane to preserve the valve hinge. A transannular patch was used in all cases. Data relating to surgical outcome, intensive care unit course, pulmonary regurgitation, and right ventricular outflow tract gradient were collected.

RESULTS

There was no mortality. Predischarge pulmonary regurgitation was ≤grade 2 in 18 (90%) patients. One patient had an outflow gradient >40 mm Hg. On follow-up of 3-24 months, there was no increase in outflow gradient; 18.7% had progression of pulmonary regurgitation.

CONCLUSION

In selected substrates, this technique is associated with minimization of pulmonary regurgitation and an excellent functional outcome. The utility of this technique needs to be validated over a longer time scale in a larger series.

Right ventricular outflow tract strategies for repair of tetralogy of Fallot: effect of monocusp valve reconstruction

OBJECTIVES

The absence of a pulmonary valve (PV) after tetralogy of Fallot (TOF) repair has been shown to impact postoperative right ventricular (RV) function. The purposes of this study were to (i) compare early outcomes after PV-sparing vs transannular patching (TAP) with monocusp valve reconstruction or TAP alone and (b) assess the mid-term results after polytetrafluoroethylene (PTFE) membrane monocusp reconstruction.

METHODS

From 2003 to 2009, 163 patients underwent TOF repair. Sixty-nine patients (42.3%) underwent a PV-sparing procedure (Group A), 74 (45.4%) underwent PTFE membrane monocusp valve reconstruction (Group B) and 20 (12.3%) underwent TAP only (Group C). Early outcomes were evaluated by the right-to-left ventricular pressure ratio, RV outflow tract gradient, tricuspid and PV function, intensive care unit (ICU) parameters and need for reintervention. Group B patients were also evaluated at intermediate term for clinical and echocardiographic parameters, including tricuspid and monocusp valve function and mobility.

RESULTS

The median age, weight and PV Z-value of Group B patients were significantly lower; 20.5 months, 9.3 kg and -4, respectively. Postoperatively, the right-to-left ventricular pressure ratio was <0.5 in all groups. Mechanical ventilation time, fluid drainage duration and total ICU stay showed no significant difference between Groups A and B, while Group C was significantly longer (P < 0.01). There were five (3%) early deaths: three from Group A and two from Group B. The incidences of moderate or severe pulmonary insufficiency (PI) on discharge were 8.2% in Group A, 9% in Group B and 50% in Group C (P < 0.001). Among Group B patients, 85% of the evaluated patients had less than moderate PI in the intermediate-term follow-up, QRS duration <140 ms in 83.3% and right-to-left ventricular diameter ratio of 0.6 ± 0.2. Two (2.6%) patients underwent reoperation for monocusp replacement. There were two (2.7%) mid-term deaths.

CONCLUSIONS

The use of a PTFE membrane monocusp valve and a valve-sparing strategy prevents immediate PI and improves short-term clinical outcomes. PTFE membrane monocusp appears advantageous in preventing severe intermediate-term PI and facilitates the preservation of RV function.

Pericardial Monocusp for Pulmonary Valve Reconstruction: A New Technique

Enhancing the pulmonary annulus renders the pulmonary valve incompetent in cases of tetralogy of Fallot. A pressure-loaded right ventricle may change to a volume-loaded ventricle, which may dilate and eventually dysfunction. This study evaluated a new technique of fashioning a monocusp valve from untreated autologous pericardium suspended on a transannular patch. It was assessed in 40 children undergoing complete repair of tetralogy of Fallot between January 2005 and December 2007. 24 patients had a transannular patch alone (group A) and 16 received a transannular patch with the autologous pericardial monocusp valve (group B). All patients were followed up for 1 year with transthoracic echocardiography to determine pulmonary insufficiency. There was no significant difference in cardiopulmonary bypass or aortic crossclamp times, postoperative chest tube drainage, duration of inotropic usage, intensive care unit or hospital stay between groups. Univariate analysis showed significantly lower grades of pulmonary insufficiency in group B. This technique for creating an autologous pericardial monocusp valve is an inexpensive, simple, and reliable procedure that effectively reduces pulmonary insufficiency at the 1-year follow-up.

Right Ventricular Outflow Tract Reconstruction With Contegra Monocuspid Transannular Patch in Tetralogy of Fallot

BACKGROUND

Pediatric diminutive right ventricular outflow tract (RVOT) reconstruction with homografts or porcine xenografts remains challenging because of limited availability, early degeneration, tissue ingrowth, and child growth. The objective of this study was to assess whether Contegra valved bovine conduit, implanted as monocuspid transannular patch, might be an interesting alternative to overcome these problems.

METHODS

We reconstructed the RVOT of 12 patients with tetralogy of Fallot, by the use of a Contegra conduit, tailored as a monocuspid valved transannular patch. The patients were 4 females and 8 males, with a mean age of 12.8 +/- 15.1 months and a mean weight of 7.2 +/- 1.9 kg. The mean pulmonary artery annulus size was 8.2 +/- 1.6 mm.

RESULTS

The Contegra tissue was suitable for suturing and for reconstruction of even severely hypoplasic RVOT. We did not observe any sign of conduit or valve degeneration during the follow-up of 28.1 +/- 17.1 months. There were no early or late deaths, and no device-related adverse events. A peak transvalvular gradient of 36.5 +/- 4.7 mm Hg was measured by echocardiography in 4 patients postoperatively, and it decreased during the follow-up to 20 +/- 7.6 mm Hg. Pulmonary valve incompetence was grade 3 in 2 patients and grade 4 in 2 patients.

CONCLUSIONS

The Contegra monocuspid transannular patch is widely applicable to RVOT reconstruction with satisfactory midterm results, particularly in patients with small pulmonary annulus. Its main advantage is to reduce the potential risk of supravalvular stenosis due to the narrowing at the distal suture line, as demonstrated when used as conduits, especially in the smaller sizes.

Initial Experience With a Bicuspid Polytetrafluoroethylene Pulmonary Valve in 41 Children and Adults: A New Option For Right Ventricular Outflow Tract Reconstruction

BACKGROUND

As the population of children with repaired congenital heart disease ages, an increasing number of patients will benefit from pulmonary valve insertion. We report our initial experience in 41 consecutive patients treated with placement of a surgically created polytetrafluoroethylene bicuspid pulmonary valve.

METHODS

A bicuspid pulmonary valve with orifice size greater than 24 mm is created with polytetrafluoroethylene and sutured into the right ventricular outflow tract. To obviate the need for reoperation in growing children, this technique is limited to older children and adults. Polytetrafluoroethylene bicuspid pulmonary valves were placed in 41 patients (age: range, 5.0 to 64.7 years, median = 15.7 years; weight: range, 14.2 to 99.0 kilograms, median, 52.0 kg). All patients had pulmonary insufficiency, pulmonary stenosis, or both, after previous intervention for tetralogy of Fallot (27), pulmonary stenosis (11), pulmonary atresia with intact ventricular septum (2), or double outlet right ventricle (1).

RESULTS

All patients left the operating theater with transesophageal echocardiography documenting no pulmonic stenosis and zero to trace pulmonic insufficiency. Median hospital length of stay was 5 days (range, 3 to 15 days; mean, 5.8 days). Follow-up including echocardiography ranged from 0.2 to 3.1 year (median follow-up, 1.5 years) and revealed significant improvement in New York Heart Association Classification, pulmonary insufficiency, and right ventricular end diastolic dimension.

CONCLUSIONS

Polytetrafluoroethylene bicuspid pulmonary valve reconstruction of the right ventricular outflow tract is a safe, effective, and durable technique for the short term. Appropriate oversizing minimizes outflow tract obstruction while maximizing competence. Long-term follow-up is necessary to determine the true value of this technique.

Annular and leaflet augmentation in Noonan's syndrome with dysplastic pulmonary valve

Two patients with dysplastic pulmonary valves associated with Noonan's syndrome successfully underwent leaflet augmentation with pericardial membrane and annular enlargement with preservation of valve competence. Both patients are doing well at 36 and 37 months, respectively, postoperatively. Echocardiography and clinical assessment showed gradients of 12 and 16 mmHg, respectively, and negligible pulmonary valve insufficiency. The surgical technique is simple and provides an attractive alternative in patients with dysplastic pulmonary valve and small pulmonary orifice and annulus.

Right Ventricle to Pulmonary Artery Reconstruction Using a Valved Homograft

Although the valved homograft is widely used to establish a connection between the right ventricle (RV) and the pulmonary artery (PA), its durability remains controversial. In the present study, the data on 141 valved homograft implantations in 107 consecutive patients performed from January 1990 to June 2000 were analyzed. The mean follow-up period was 4.6 years (range, 0.2-9.4 years). The clinical data, including clinic records, operative notes, follow-up visits, and letters from referring physicians, were analyzed with particular reference to variables associated with early and late mortality, deterioration of the homograft, and risk factors for patient survival and homograft failure. Early death occurred in 7.5% (n=8) of the cases, and each of these patients died without leaving the hospital. Late death occurred in 2 patients, for whom the cause of death was suggested to be related to arrhythmia. Thirteen patients underwent catheter intervention (ie, balloon dilatation and/or stenting) and 8 of these did not require homograft replacement following catheterization. The overall survival rate at both 3 years and 5 years was 88.9+/-3.4%. Cumulative freedom from total homograft failure was 82.5+/-3.6% at 1 year; 61.6+/-5.0% at 3 years; and 42.4+/-6.2% at 5 years. In comparison with 2 criteria of homograft failure (ie, total homograft failure and homograft failure including catheter intervention), the incidence of freedom from homograft failure including catheter intervention was lower than that of total homograft failure, although the difference was not statistically significant. In the multivariate analysis, significant risk factors with respect to patient survival were homograft replacement and the use of expanded polytetrafluoroethylene (ePTFE); those judged to be significant with respect to homograft failure were total repair with first homograft implantation and diagnosis of truncus arteriosus. The valved homograft was thus considered an appropriate choice of conduit between the RV and the PA, and it provided excellent patient survival. However, this type of homograft did not provide a completely permanent solution for the repair of complex cardiac anomalies. Therefore, the use of ePTFE for homograft extensions should be avoided. Finally, the results suggest that catheter intervention plays an important role in the longevity of the implanted homograft.

Pericardial tissue valves and Gore-Tex conduits as an alternative for right ventricular outflow tract replacement in children

BACKGROUND

There is still no perfect conduit for reconstruction of the right ventricular outflow tract (RVOT) in children. Homografts are not always available in the appropriate size, and degenerate in a few years. This study evaluates the pericardial valve with Gore-Tex conduit as an alternative for RVOT construction.

METHODS

From January 1, 1993, to September 30, 1999, a pericardial tissue valve was inserted in all patients undergoing RVOT reconstruction or pulmonary valve replacement (PVR) who were large enough to accommodate a tissue valve. In patients without a native main pulmonary artery, a new technique was used to construct an RV-PA conduit out of a flat sheet of Gore-Tex, as Dacron frequently leads to stenosis. Data were collected by retrospective review, follow-up echocardiograms, and assessment by a single cardiologist.

RESULTS

There were 48 patients, 22 undergoing a PVR alone and 26 a RV-PA valved Gore-Tex conduit. Diagnosis included tetralogy of Fallot (n = 25); truncus arteriosis (n = 9); ventricular septal defect with PA (n = 5); DORV (n = 4); D-TGA with PS (n = 2); and 1 each IAA with sub AS, VSD with PI, and PS s/p Ross procedure. Patient age ranged from 3 to 33 years and 98% were reoperations. The valve sizes ranged from 19 to 33 mm and the median hospital length of stay was 4 days. There were 2 (4.2%) perioperative and 1 (2.1%) late deaths, none related to the valve or Gore-Tex conduit. At a follow-up of 15 to 86 months (mean 43 +/- 16 months), all remaining 45 patients are New York Heart Association class I, all valves are functional, and no patient has required valve or conduit replacement or revision; more importantly, echocardiogram revealed no significant valve or conduit stenosis (mean gradient 16 +/- 8 mm Hg) and no evidence of regurgitation or structural degeneration.

CONCLUSIONS

A pericardial tissue valve and Gore-Tex conduit provides a reliable alternative for RVOT reconstruction in pediatric patients. It is readily available, molds in the limited retrosternal space, and has outstanding intermediate results with no evidence of failure or deterioration up to 7 years after insertion.