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Ann Thorac Surg 2000;70:1511-1514
© 2000 The Society of Thoracic Surgeons

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Original articles: cardiovascular

Expanded polytetrafluoroethylene monocuspid valve for right ventricular outflow tract reconstruction

^a Department of Cardiac Surgery, Kinki University School of Medicine, Osaka, Japan

Address reprint requests to Dr Iemura, Department of Cardiac Surgery, Kinki University School of Medicine, 377-2 Ohono-Higashi, Osaka-Sayama, Osaka 589-8511, Japan
e-mail: singe{at}med.kindai.ac.jp

	Abstract

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Background. Numerous materials have been used for reconstruction of the right ventricular outflow tract (RVOT) in patients with complex congenital heart defects.

Methods. Between January 1982 and March 1999, 19 patients (10 boys and 9 girls; mean age, 8.5 years) with severe RVOT obstruction underwent reconstruction using a transannular patch and expanded polytetrafluoroethylene (ePTFE) monocuspid valve.

Results. There were no perioperative deaths. Postoperatively, the mean ± standard deviation RVOT gradient was 12 ± 9 mm Hg. Echocardiography showed good motion of all cusps, and most had no or trivial pulmonary regurgitation. The difference between the preoperative and postoperative mean ratio of right-to-left ventricular peak systolic pressure was significant (p = 0.0001). In the 8 patients followed for 3 years or longer, pulmonary regurgitation was mild or better in 5 and moderate in 2, and the mean peak systolic RVOT gradient was 16.3 ± 5.9 mm Hg. Five patients had good mobility of the monocusps. Two patients needed reoperation because of stenosis at the distal anastomosis of the transannular patch; 1 patient died.

Conclusions. The ePTFE monocuspid valve may be useful in reconstruction of the RVOT.

	Introduction

Top Abstract Introduction Material and methods Results Comment References

 
Numerous techniques and materials have been used to prevent pulmonary regurgitation after reconstruction of the right ventricular outflow tract (RVOT) in patients with complex congenital heart defects, but none has proved to be superior to the others. Here we report our experience with a monocuspid valve constructed of expanded polytetrafluoroethylene (ePTFE) attached to a transannular patch in reconstruction of the RVOT.

	Material and methods

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Patients
Between January 1982 and March 1999, 19 patients (10 boys and 9 girls; mean age, 8.5 years, range, 1 to 16 years) with severe RVOT obstruction underwent reconstruction of the RVOT using a transannular patch with a monocuspid valve made of ePTFE. The patients’ mean ± standard deviation body surface area (BSA) was 0.95 ± 0.42 m² (range, 0.39 to 1.66 m²). For 3 patients with tetralogy of Fallot, the operation was their primary corrective procedure. The other 16 patients in the series had previously undergone operation for tetralogy of Fallot (n = 7), pulmonary atresia with a ventricular septal defect (n = 3), transposition of the great arteries (TGA) with intact ventricular septum (n = 2), TGA with pulmonary artery stenosis and a ventricular septal defect (n = 1), corrected TGA (n = 2), or a double-outlet right ventricle (n = 1). Previous procedures or materials [1, 2] used in those patients are listed in Table 1. One patient with tetralogy of Fallot underwent the same operation twice within 4 months because infective endocarditis developed in a segment of the reconstructed RVOT; therefore, there was a total of 20 operations in this series.

The monocusp (Fig 1A) was constructed of 0.1-mm-thick ePTFE sheet material (Gore-Tex, W.L. Gore & Assoc, Flagstaff, AZ). The transannular patch was prepared from a longitudinally cut and trimmed Dacron vascular graft (Veri-Soft Vascular Graft, Boston Scientific Corp, Wayne, NJ) in the first 3 operations and an ePTFE prosthetic vascular graft (Gore-Tex Vascular Graft, W.L. Gore & Assoc) in the subsequent 17 operations. The transannular patch was placed so that the upper margin of the cusp was 2 to 3 mm higher than that of the hypoplastic native pulmonary valve (if preserved) or native pulmonary annulus (Fig 1B). In 5 of the 8 patients with a hypoplastic pulmonary valve, the primary corrective operation included use of the two-cusp plasty [3] to enlarge the native pulmonary valve area.

View larger version (12K): [in this window] [in a new window]   Fig 1. Use of a monocusp made of a 0.1-mm-thick expanded polytetrafluoroethylene (ePTFE) sheet. (A) On the monocusp itself, the distance from a to b and the distance from d to e are each about 5 mm and parallel to each other. In this area, the monocusp occludes the pulmonary annulus. The distance from a to e and the distance from b to d are each equal to the width of the transannular patch at the segment corresponding to the pulmonary annulus (excluding the width of the sewing edge). The trimmed line a–e has a shallow curve. The distance from f to c is about 75% of the distance from b to d. (B) Operative schema. The transannular patch with the ePTFE monocusp attached is sewn to the stenotic right ventricular outflow tract.

Paired t tests were used to compare preoperative and postoperative data. A p value less than 0.05 was considered statistically significant.

	Results

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There were no deaths during the surgical procedures and no postoperative hospitalizations. During follow-up, there were no cases of hemolysis or thrombosis. All patients underwent echocardiographic studies to assess pulmonary valve function after operation.

Postoperatively, all patients had normal biventricular function. The mean right ventricular peak systolic pressure was 48 ± 13 mm Hg (range, 36 to 85 mm Hg). The mean ratio of right-to-left ventricular peak systolic pressure was 0.49 ± 0.12 (range, 0.31 to 0.65). The mean of the peak-to-peak systolic pressure gradients across the RVOT was 12 ± 9 mm Hg (range, 0 to 28 mm Hg; Table 2). Preoperatively, these three values had been 96 ± 40 mm Hg, 0.97 ± 0.35, and 53 ± 20 mm Hg, respectively. The difference between the preoperative and postoperative mean ratio of right-to-left ventricular peak systolic pressure was significant (p = 0.0001; Fig 2). Postoperative echocardiography showed good motion of all cusps and little pulmonary regurgitation (Table 2). All patients were discharged from the hospital in good condition.

View larger version (18K): [in this window] [in a new window]   Fig 2. Ratio of right-to-left ventricular (RV/LV) peak systolic pressure in 19 patients preoperatively (preop.) and postoperatively (postop.). Vertical lines indicate means ± standard deviation. The difference between the preoperative and postoperative values is significant (p = 0.0001 on paired t test). Asterisks indicate patients who underwent primary repair of tetralogy of Fallot.

All 8 patients underwent color Doppler echocardiographic monitoring for the development of pulmonary regurgitation during follow-up or before reoperation (mean interval between the initial operation and the most recent echocardiographic study, 62.4 months; range, 24 to 149 months); the results are shown in Table 2. In all 5 patients with trivial or mild pulmonary regurgitation, the monocuspid valve had good motion. In the 2 patients with moderate regurgitation, monocuspid valve function was lost. In 1 patient, the monocuspid valve became fixed in a half-open position and mild stenosis developed across it (gradient, 15 mm Hg). In the other patient, the monocusp could not be detected by echocardiography, probably because it was fixed in the fully open position and adherent to the transannular patch. This monocusp had been made larger than the others to cover a large pulmonary annular area (3.8 cm²), but the patient was relatively small (BSA = 0.95 m²).

Postoperative echocardiography in the patients with midterm results also showed a mean peak pressure gradient across the monocusp of 16.3 ± 5.9 mm Hg (range, 10 to 25 mm Hg) in the 7 living patients who were followed for 3 years or longer. In all these patients, including those who required reoperation, the pressure gradient was considered to be acceptable.

	Comment

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Among the materials and methods used to repair a hypoplastic RVOT and pulmonary trunk are a transannular patch with a monocuspid valve constructed from autologous pericardium [4], tanned bovine pericardium [5], porcine pericardium [6], synthetic materials [7], or other substances [8, 9]. Long-term results with all these materials have been unsatisfactory, principally because they do not grow with the child and sometimes may even shrink, resulting in progressive stenosis. Moreover, none of these materials has proved to be superior to the others.

Although the use of annular patches without valves avoids stenotic changes and subsequent operation to treat stenosis, pulmonary regurgitation and right ventricular dysfunction develop postoperatively and require surgical correction [10]. An incorporated monocuspid valve should reduce or abolish postoperative pulmonary regurgitation and decrease right ventricular volume overload, at least in the short term. Therefore, use of a cusp that prevents pulmonary regurgitation may provide better results than a reconstruction that does not include valves. However, if stenotic changes develop in the cusp, the RVOT may become obstructed and an additional surgical procedure will be needed.

Vascular grafts, sutures, and patches made of ePTFE have been found to be reliable and durable. A monocuspid valve constructed from a sheet of ePTFE should be freely mobile and not degenerate over time. In our series, short-term results with the ePTFE monocuspid valve were satisfactory. At midterm, the monocusp was moving well and was well tolerated hemodynamically in 5 of 8 patients. The reason for an additional surgical procedure in the 2 patients who underwent reoperation after RVOT reconstruction was stenosis at the distal junction of the native pulmonary artery and transannular patch, not cusp deterioration.

The mean CSAI of the reconstructed pulmonary annulus in the patients in our study was 3.0 cm²/m². According to Oku and colleagues [11], the optimal CSAI in patients undergoing correction of tetralogy of Fallot is 2.0 to 2.5 cm²/m². In our series, we made the new pulmonary annulus larger to allow for the children’s growth. One monocuspid valve that was attached to an especially large annulus (CSAI = 4.0 cm²/m², with 3.8 cm² covered by the monocusp) lost mobility during midterm follow-up, probably because it adhered to the transannular patch. Thus, although a larger structure is attractive with respect to accommodating patients’ growth, the monocusp can lose mobility relatively soon after reconstruction [12].

Bioprosthetic valves generally function well early after operation, although deterioration of valve function has been reported to occur sooner in children than in adults and to result in severe stenosis requiring additional intervention [7]. We found that, unlike bioprosthetic valves, the ePTFE monocuspid valve continued to function without severe stenotic changes for 3 years or longer. In the 1 patient with deterioration of the ePTFE monocuspid valve, regurgitation progressed gradually over time and resulted in a mild worsening of hemodynamic status. This outcome was more similar to the hemodynamic changes observed during long-term follow-up in patients with conduits without valves than to the severe hemodynamic disturbances that occur in patients with valve stenosis. Our experience indicates that most patients with an ePTFE monocuspid valve may be able to avoid additional operation for cusp-related stenotic complications for a long time.

In conclusion, although we did not find ePTFE to be the ideal material for monocuspid valve construction, its relatively long durability and limited stenotic deterioration may make it a better choice than other materials used in RVOT reconstruction. Comparison studies of these materials are needed.

	References

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