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Ann Thorac Surg 1996;61:1811-1815
© 1996 The Society of Thoracic Surgeons

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Original Article: Cardiovascular

Autologous Monocusp Pulmonary Valve: Preliminary Results

Departments of Cardiothoracic Surgery and Pediatric Cardiology, Beilinson Medical Center, Petach Tikva, and Department of Cardiothoracic Surgery, Hadassah Medical Center, Jerusalem, Israel

Accepted for publication February 21, 1996.

	Abstract

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Background. There is growing recognition that postoperative pulmonary regurgitation may result in early or late progressive right heart failure.

Method. A technique for fashioning an autologous monocusp pulmonary valve from the wall of the pulmonary artery was developed. The monocusp valve was fashioned from the anterior wall of the main pulmonary artery, and the remaining defect was filled with autologous pericardium. The procedure was performed in 8 dogs and 5 children.

Results. Early follow-up and serial echocardiographic assessment in both dogs and children proved the functionality of this monocusp pulmonary valve. All valves were pliable and demonstrated mild to moderate pulmonary stenosis and insufficiency.

Conclusions. Construction of the autologous monocusp pulmonary valve is a feasible technique, and the valve performs efficiently. The acute performance in the canine model was excellent, and preliminary midterm results in the clinical study are reasonable. It is logical to assume that the monocusp, being an integral part of the arterial wall, will retain its viability and share in the subsequent growth of the pulmonary artery. Should follow-up studies demonstrate its long-term competence, this autologous valve may provide a good solution for various forms of pulmonary regurgitation and be useful in pulmonary autograft replacement of the aortic valve.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Severe pulmonary regurgitation and right ventricular dilatation are known complications after surgical correction of various forms of right ventricular outflow tract obstruction, including repair of tetralogy of Fallot with transannular enlargement, absent pulmonary valve complex, and valvular and supravalvular pulmonic stenosis requiring transannular enlargement or valvectomy.

It is increasingly recognized that postoperative pulmonary regurgitation may result in progressive right heart failure [1–6]. This may be significant in the immediate postoperative period, especially when associated with tricuspid regurgitation, distal pulmonary stenosis, pulmonary hypertension, or poor right ventricular function [7, 8], as well as years later [1–6]. Some of these patients subsequently require placement of a pulmonary valve. Creation of a functional pulmonary valve as part of the primary surgical repair may thus avoid these complications in the short and long term.

In pulmonary autograft replacement of the aortic valve (Ross procedure), it is usually necessary to replace the pulmonary valve using a homograft in this position. Subsequent replacement of this homograft, due to degenerative deterioration of valve function, is usually required. The creation of a functional pulmonary valve using autologous tissue, which will retain its viability, may avoid the need for homografts in the pulmonary position and their subsequent replacement.

This is a preliminary report on the development and experimental testing of an autologous monocusp pulmonary valve derived from the wall of the pulmonary artery in the canine model. We also report its performance in 5 children.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
The experimental study was conducted on 8 mongrel dogs weighing 15 to 30 kg (mean, 22 kg). Anesthesia was induced with sodium pentobarbital (30 mg/kg) and pancuronium bromide (0.1 mg/kg), and followed by endotracheal intubation. Anesthesia was maintained by 0.5% to 2% halothane in room air with a volume preset ventilator, supplemented with fentanyl (0.02 mg/kg intravenously). After a midsternotomy was made, hypothermic cardiopulmonary bypass with potassium cardioplegic myocardial preservation was used. With the chest open, a pericardial patch was excised, and the aorta, superior vena cava, and inferior vena cava were cannulated. Cardiopulmonary bypass was established, and the pulmonary artery was precisely and carefully dissected from the aorta. All fatty tissue covering the anterior wall of the pulmonary artery was removed, and a crescentic transverse incision was made along its anterior hemicircumference at the pulmonary annulus level. The pulmonary leaflets were completely removed, and another crescentic incision was made facing the former one (one diameter of the pulmonary artery distally on the anterior wall of the pulmonary artery) (Fig 1A). The distal edge of the proximal incision was sutured to the posterior wall of the pulmonary artery, creating a monocusp valve (Figs 1B, 2). The defect in the anterior wall of the pulmonary artery was then covered by a pericardial patch, which should usually be half the circumference of the pulmonary artery (Figs 1C, 1D). The aortic cross-clamp was removed. The dog was rewarmed, bypass was gradually discontinued, and the cannulas were removed. After hemodynamic stabilization was achieved, pressure in the right ventricle and pulmonary artery was measured and an epicardial echocardiographic study was performed. All animals were then sacrificed (sodium bicarbonate infusion) and their hearts examined to ascertain that the pulmonary valve had been completely removed and the monocusp correctly constructed.

View larger version (48K): [in this window] [in a new window]   Fig 1. . Frontal view of the pulmonary artery: (A) Proximal and distal transverse incision in the main pulmonary artery. (B) Suturing the distal edge of the proximal incision to the posterior wall of the pulmonary artery creating a monocusp valve. (C, D) Closing the defect in the pulmonary artery wall with pericardial patch.

View larger version (70K): [in this window] [in a new window]   Fig 2. . Schematic drawing showing the autologous monocusp in a closed and open position before it is covered with a pericardial patch.

Five children, aged 8 months to 5 years, with severe pulmonary stenosis associated with various congenital cardiac malformations (Table 1) have been treated with this technique using the same procedure as in the animal study, except that the pericardial patch was used as a transannular patch onto the right ventricular outflow tract. The children were followed up clinically and echocardiographically during the immediate postoperative period and 1 to 12 months thereafter. Pulmonary insufficiency was detected with color Doppler echocardiography and defined as mild if there was no retrograde flow seen in the main pulmonary artery using pulsed Doppler echocardiography distal to the monocusp position or moderate if retrograde flow was seen in the main pulmonary artery but without evidence of volume overload of the right ventricle. Pulmonary insufficiency was defined as severe if both retrograde flow and volume overload were seen in the right ventricle.

	Results

Top Footnotes Abstract Introduction Material and Methods Results Comment References

View larger version (66K): [in this window] [in a new window]   Fig 3. . Echocardiographic study in dogs: Monocusp in open (A) and closed (B) positions, showing minimal pulmonary valve regurgitation (late). mc = monocusp; PA = pulmonary artery; RV = right ventricle.)

View larger version (89K): [in this window] [in a new window]   Fig 4. . (A) Short-axis view of the pulmonary monocusp in the closed position obtained 1 day after operation in a 1-year-old child. (B) Doppler signal obtained from the same child distal to the monocusp indicating a minimal degree of retrograde flow during diastole. Ao = aorta; LA = left atrium; PA = pulmonary artery; PMC = pulmonary monocusp; RV = right ventricle.)

View larger version (123K): [in this window] [in a new window]   Fig 5. . Doppler echocardiogram obtained from patient 1 one year after operation, indicating a minimal degree of retrograde flow (arrows) was detected in the main pulmonary artery (PA) distal to the monocusp. (RPA = right pulmonary artery.)

	Comment

Top Footnotes Abstract Introduction Material and Methods Results Comment References

Standard methods to prevent or repair pulmonary regurgitation have included: valve replacement, valved conduits, or the creation of pericardial monocusp valves, the available long-term results of which have not been satisfactory. The experience of Laks and colleagues [14–20] showed the tendency of heterograft valves to calcify and degenerate prematurely in children, leading to their abandonment in pediatric cases. The use of a pericardial monocusp valve also resulted in uniform late failure [21], and the use of an allograft as a valve conduit in infants will also require late replacement because of its inadequate size as the child grows up. The use of a homograft in the pulmonary position is required as part of the Ross procedure. This homograft will also require late replacement due to valve deterioration and lack of growth.

The aim of this study was to develop a competent valve with no systolic gradient that could be constructed from viable autologous tissue. Theoretically, the valve described above has several advantages: It is fashioned from viable autologous tissue, derived from the pulmonary artery wall, and remains a part of the pulmonary artery itself. In its normal resting position, the flap, acting as a monocusp valve, tends to close the pulmonary artery lumen completely. Thus, even a low pressure gradient across the autologous monocusp pulmonary valve during diastole easily closes it. The same pericardial patch, used to close the pulmonary artery defect, can also be used to augment the right ventricular outflow tract, as a transannular patch. The valve can be constructed quickly and easily during coronary perfusion.

The good early results obtained in our canine study-a functioning valve, with minimal systolic gradient and only mild incompetence-encouraged us to apply this method of creating the autologous monocusp pulmonary valve in 5 children. Their early postoperative course was smooth in all the children, and echocardiographic studies before discharge and at the end of the follow-up period showed a well-functioning valve with mild to moderate insufficiency and stenosis.

We believe that with more experience it is feasible to create a valve for children with the lower gradient and competency achieved in the canine model. It is extremely important to dissect and remove all fat and excessive tissue adhering to the main pulmonary artery to make the monocusp a pliable functioning valve. In some patients, the histology of the pulmonary artery wall is abnormal and may restrict the free motion of the newly formed valve. In such a situation, this technique cannot be used.

The role of valve function depends on the ideal size of the patch covering the defect: too large a patch will cause insufficiency and too small a patch will cause stenosis. The patch should usually be half the circumference of the pulmonary artery. In cases of hypoplastic main pulmonary artery, which is often seen in tetralogy of Fallot, the size of the anterior monocusp is somewhat limited, and the size of the patch covering the defect is too large for the creation of a competent valve. However, we believe that mild to moderate pulmonary insufficiency, even at the cost of some pulmonary stenosis (not more than moderate), is superior in the long-term over free pulmonary insufficiency as seen in patients undergoing transannular patching with respect to right ventricular dilatation and failure. It is also important to create the two crescentric incisions exactly half of the pulmonary artery circumference in size, to create a monocusp that will close the pulmonary artery without causing stenosis.

A pliable valve was demonstrated even after 12 months, and there was no deterioration in valve function during the follow-up period (21 days to 12 months; mean, 8 months). It is reasonable to assume that the phenomena of deterioration and calcification, which affect valves made of heterologous tissue [22, 23], should not occur with an autologous valve. It is also reasonable to assume that being an integral part of the arterial wall, it will retain its viability and share in the subsequent growth of the pulmonary artery.

A long-term study will be necessary to ascertain if the autologous monocusp pulmonary valve remains a viable and competent valve, and if it grows with the child as seen in other implanted autologous tissue [24].

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Address reprint requests to Dr Vidne, Department of Cardiothoracic Surgery, Beilinson Medical Center, Petach Tikva, Israel 49100.

	References

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 

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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Amir Elami Bernardo A. Vidne Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mishaly, D. Articles by Vidne, B. A. Search for Related Content PubMed PubMed Citation Articles by Mishaly, D. Articles by Vidne, B. A.