Eur J Cardiothorac Surg 1999;16:26-31
© 1999 Elsevier Science NL
Ventricular outflow tracts after Kawashima intraventricular rerouting for double outlet right ventricle with subpulmonary ventricular septal defect
Youichi Kawahira,
Toshikatsu Yagihara,
Hideki Uemura,
Toru Ishizaka,
Yoshiro Yoshikawa,
Ko Yoshizumi,
Soichiro Kitamura
Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565 Japan
Corresponding author. Tel.: +81-6-68335012; fax: +81-6-68727486
e-mail: ykawahir{at}hsp.ncvc.go.jp
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Abstract
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Objective: To determine whether or not the ventricular outflow tracts can be efficiently constructed in patients with double outlet right ventricle with subpulmonary ventricular septal defect by the Kawashima intraventricular rerouting in which the morphologically right ventricular outlet is divided into two, one for the systemic and the other for the pulmonary circulations. Methods: The intraventricular rerouting procedure was carried out in nine patients with this particular malformation. Age at repair ranged from 35 days to 3 years old. The distance between the attachments of the tricuspid and the pulmonary valves was 10 mm or greater in all except one patient in whom the measured value was 3 mm. Resecting subaortic musculature appropriately, a tailored patch, either oval-shaped (in seven) or heart-shaped (in two), was placed to construct an unobstructed channel for the left ventricular outflow tract with its diameter greater than that of the anticipated normal aortic orifice at the time of repair. For an unobstructed channel to the pulmonary arteries, enlargement of the right ventricular outflow tract was carried out using a patch in six. Results: All patients survived the operative procedure. On postoperative catheterization, mean pulmonary arterial pressure was 15±8 mmHg, and cardiac index was calculated as 3.3±0.6 l/min per m2. It proved that the constructed left ventricular outflow tract can become larger in the longer term. Pressure gradient across the left ventricular outflow tract was greater than 20 mmHg in two patients in the intermediate term. One of these two underwent reoperation for the obstruction 10 years after the initial repair. It was suspected that use of a heart-shaped internal conduit, which seems to result from inadequate conal resection, was one of the possible causes of such obstruction in the longer term. Pressure gradient of 47 mmHg was seen across the right ventricular outflow tract in one patient, although this patient has undergone no reoperation. Enlargement of the right ventricular outflow tract could minimize postoperative obstruction for the pulmonary pathway. Conclusions: The intraventricular rerouting remains one of the attractive surgical options for repair in this particular setting, in terms of successful construction of the ventricular outflow tracts.
Key Words: Double outlet right ventricle • Subpulmonary ventricular septal defect • Kawashima intraventricular rerouting • Right ventricular outflow tract obstruction • Left ventricular outflow tract obstruction
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1. Introduction
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In patients with double outlet right ventricle with subpulmonary ventricular septal defect (VSD) with adequate distance between the tricuspid valve and the pulmonary valve, intraventricular rerouting is one of the operative procedures for repair, placing an internal conduit between attachments of the pulmonary and the tricuspid valves [1]. Either the subaortic or the subpulmonary channel could become obstructive after this procedure, since the outlet portion of the morphologically right ventricle is divided into two, one for the left ventricular outflow tract through the VSD and the other for the right ventricular outflow tract.
The arterial switch procedure, which is undoubtedly optimal in patients with double outlet right ventricle with subpulmonary VSD possessing antero-posterior orientation of the ascending aorta and the pulmonary trunk [2–4], is obviously one of the attractive surgical options also in the setting of side-by-side arrangement of the great arteries [5]. Our preference, nonetheless, has been the Kawashima intraventricular rerouting in this particular circumstance, considering some morphologic characteristics including the patterns of the coronary arteries [3]. Our experience of this procedure was herein described to determine whether the ventricular outflow tracts become obstructive or not in the intermediate term.
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2. Materials and methods
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Between August 1986 and June 1997, 22 patients with double outlet right ventricle with subpulmonary VSD underwent biventricular repair at our institution. Of these, the Kawashima intraventricular rerouting was indicated in nine patients in whom distance between the attachments of the tricuspid and the pulmonary valves was relatively large [2,3]. Age at repair ranged from 35 days to 3 years old with a mean of 16 months, and body weight from 2.5 kg to 12.3 kg (a mean, 7.6 kg). Associated malformations were coarctation of the aorta in five patients, mild pulmonary stenosis in two, moderate subaortic stenosis in three, additional muscular VSD in one, and mitral regurgitation in one. The aortic arch had been previously reconstructed in four patients. Including these four, the pulmonary trunk had been banded in five. In the remaining four patients, no previous procedure had been carried out.
Intracardiac maneuvers were carried out through a median sternotomy, with the aid of cardiopulmonary bypass and induced cardiac arrest using crystalloid cardioplegic solution. Intracardiac morphology was initially confirmed paying particular attention to the distance between the attachments of the tricuspid and the pulmonary valves. The distance was 10 mm or greater in all except one patient in whom the measured value was 3 mm (Table 1). Subaortic musculature was resected as appropriate without injury to the aortic valve and the tension apparatus of the tricuspid valve (Fig. 1). In particular, this maneuver was extensively carried out in three patients with moderate subaortic stenosis (Patients 7, 8, and 9), resecting parts of the outlet septum and the ventriculo-infundibular fold. The interventricular communication was enlarged in three patients to avoid obstruction at the VSD level.
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Table 1. Reconstruction of left and right ventricular outflow tract. IC, internal conduit; LVOT, left ventricular outflow tract; VSD, ventricular septal defect; RVOT, right ventricular outflow tract; PT, pulmonary trunk.
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Fig. 2. In a patient with the tricuspid-pulmonary distance of 3 mm, the suture line for attaching the internal conduit was extended onto the wall of the pulmonary trunk, removing the posterior leaflet of the pulmonary valve.
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Fig. 1. Schematic drawings of the operative procedures. Resecting parts of the outlet septum and subaortic musculature, an internal conduit, either oval-shaped or heart-shaped, was placed for intraventricular rerouting between the attachments of the tricuspid and the pulmonary valves.
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An internal conduit was designed to be sufficiently large so as to construct an unobstructed channel for the systemic circulation with its diameter greater than that of the anticipated normal aortic orifice [6,7]. The internal conduit was either oval-shaped or heart-shaped (Table 1). Equine pericardium was the prosthetic material used for the internal conduit in five, and bovine pericardium in four. In the patient with 3 mm of the tricuspid-pulmonary distance, the posterior leaflet of the pulmonary valve was removed and the suture line for the internal conduit was extended to the wall of the pulmonary trunk (Fig. 2). By this modification, width of own tissue for the constructed channel for the left ventricular outflow tract became 18 mm. The intracardiac maneuver for attaching the internal conduit was carried out via a right ventriculotomy in six patients, and via a right atriotomy in the other three.
An additional muscular VSD seen in one patient was primarily closed. In another patient with mitral regurgitation, plasty to the regurgitant valve was concomitantly employed.
The right ventricular outflow tract was enlarged using a ventricular patch in four, and using a transannular patch in two. The pulmonary trunk, which had been previously banded, was augmented placing a patch in two of three patients in whom no incision was made on the right ventricle.
Postoperative cardiac catheterization was carried out 0.9–11 years (a mean 3.3±3.2 years) after repair. Obstruction across the ventricular outflow tract was considered significant when pressure gradient was greater than 20 mmHg between either the aorta or the pulmonary trunk and its ventricle. Postoperative echocardiography was consecutively carried out during the follow-up term of 1.3–12.1 years (6.3±2.4 years). For statistical analysis, Student's t-test, as well as chi-square analysis, were employed. The Kaplan-Meier method was used to calculate the time-related survival ratio.
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3. Results
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All the nine patients survived the operative procedure. One patient (Patient 3), however, died 3 years after repair because of respiratory problem. Actuarial survival rate was 83% at 5 and 10 years after repair.
Postoperative ventriculography showed that end diastolic volumes of the left and the right ventricles were 133±38% (93–222%) and 131±53% (90–240%) of the anticipated normal values, respectively. Ejection fractions of the left and the right ventricles were 0.66±0.11 (0.50–0.83) and 0.48±0.09 (0.35–0.58), respectively. Right atrial pressure was 5±3 mmHg (2–10 mmHg), and end diastolic pressure of the left ventricle was 9±4 mmHg (4–18 mmHg). Pulmonary arterial pressure was 15±8 mmHg (6–33 mmHg), and cardiac index was calculated as 3.3±0.6 l/min per m2 (2.4–4.2 l/min per m2). Consecutive echocardiography showed no significant regurgitation across either the aortic or the mitral valve. In one patient, moderate regurgitation occurred across the tricuspid valve one year after the repair.
Postoperative obstruction of the left ventricular outflow tract progressed in two patients (Table 2), pressure gradient across the channel becoming 69 mmHg at 10 years and 23 mmHg at 2 years after repair, respectively. Progression of the obstruction was not affected by the ratio of the width of the narrowest portion of own tissue to the circumference of the constructed left ventricular outflow tract (P=0.22) nor by the size of the left ventricular outflow tract designed at the time of repair (P=0.48) (Table 1). The shape of the internal conduit, in contrast, was heart-shaped in the two patients with obstruction, while oval-shaped in the other seven without (P=0.0001). The patient with significant pressure gradient of 69 mmHg underwent reoperation 10.8 years after the initial repair. The heart-shaped internal conduit previously used had produced a tortuous channel, and marked proliferation of fibrous tissues was seen on the systemic circulation side of the prosthetic material around the most tortuous part. Removing extensively these tissues, alternative intraventricular rerouting was successfully carried out using an oval-shaped internal conduit. In the patient in whom the suture line for the internal conduit was extended onto the wall of the pulmonary trunk (Patient 1), no significant pressure gradient was present across the left ventricular outflow tract, and diameter of the channel had become greater than that initially designed (Fig. 3).
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Table 2. Consecutive findings at cardiac catheterization and echocardiography.  P(RV-PA), pressure gradient between right ventricle and pulmonary arteries; P(LV-Ao), pressure gradient between left ventricle and aorta; LVOT, left ventricular outflow tract; RVOT, right ventricular outflow tract; TR, tricuspid regurgitation.
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Fig. 3. Diameter of the constructed left ventricular outflow tract [{(width of internal conduit+width of own tissue)-8}/3.14 (mm)] [6] in comparison with the anticipated normal value for the aortic orifice (16.6xbody surface area0.6) [7]. Its diameter designed at the time of repair (white dots) had changed by the time of postoperative catheterization (black dots). The channel became smaller than the anticipated normal aortic orifice in Patients 4 and 8 in whom pressure gradient across the left ventricular outflow tract was greater than 20 mmHg in the longer term. In Patients 2 and 3, placement of a transannular patch was needed for reconstruction of an unobstructed right ventricular outflow tract, because of bulging of the large internal conduit towards the subpulmonary region. In the remaining five patients, the diameter of the left ventricular outflow tract became larger. It is obvious that own tissues of the channel became wider in association with somatic growth.
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As for obstruction of the right ventricular outflow tract, significant pressure gradient of 47 mmHg was seen in one patient (Table 2). In this particular patient, right ventriculography 4 years after repair demonstrated a squeezed channel between the anterior wall of the right ventricle and the internal conduit. In the other eight patients, no progressive obstruction was detected by consecutive echocardiography. The initial size of the constructed left ventricular outflow tract was not related to progression of obstruction across the right ventricular outflow tract in the intermediate term. A proportionally large channel for the left ventricular outflow tract, nonetheless, needed placement of a transannular patch (Table 1, Fig. 3). In six patients in whom the right ventriculotomy was made, significant obstruction of the right ventricular outflow tract was absent even in the intermediate term, while significant pressure gradient across the channel was seen in one of the three patients without enlargement of the right ventricular outflow tract.
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4. Discussion
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When double outlet right ventricle is surgically repaired, location of the interventricular communication should be precisely determined. In patients with subaortic VSD, the channel to be constructed from the left ventricle to the aortic orifice within the right ventricle is usually neither long nor tortuous, and placement of the internal conduit can be achieved without affecting the other channel from the right ventricle to the pulmonary arteries. In those with doubly-committed VSD, rerouting from the left ventricle to the aorta can be readily achieved. In this rare setting, however, the internal conduit may produce subpulmonary obstruction. In those with non-committed VSD, construction of an unobstructed channel for the left ventricular outflow tract is commonly difficult. Placement of the internal conduit, when interventricular rerouting is feasible, would not markedly influence on the subpulmonary channel, since the interventricular communication is located remote from the pulmonary orifice. In this respect, the internal conduit can be long and tortuous, and the subpulmonary channel can become narrow if the Kawashima intraventricular rerouting is employed in patients with subpulmonary VSD.
In our present study, reoperation has been thus far needed for postoperative obstruction across the left ventricular outflow tract in one of nine patients (11%). In another series of our patients having double outlet right ventricle, such reoperation was needed in two of 62 operative survivors with subaortic VSD (3%), in none of seven with doubly-committed VSD (0%), three of 10 with non-committed VSD (30%), and in one of nine with atrioventricular septal defect and a common valve (11%). Between these groups, incidence of reoperation was higher in patients with non-committed VSD and lower in those with subaortic or doubly-committed VSD (P=0.04).
When the arterial switch procedure is employed in patients with subpulmonary VSD, rerouting is needed from the left ventricle to the native pulmonary valve within the right ventricle. In such circumstance, therefore, orientation of VSD is metamorphosed into a subaortic type. Nine of our 22 patients with subpulmonary VSD undergoing repair between August 1986 and June 1997 had the ascending aorta located anteriorly to the pulmonary trunk, and there was a fibrous continuity present between the tricuspid and the pulmonary valves. In these patients, the arterial switch procedure was employed, which was considered optimal, with no operative death. Postoperative obstruction across the left ventricular outflow tract has been noted in one of 9 (11%), with a pressure gradient of 31 mmHg. With this result, the arterial switch procedure could also have provided an excellent result, in terms of the left ventricular outflow tract, even in patients with subpulmonary VSD and side-by-side arrangement of the great arteries in whom the Kawashima intraventricular rerouting was chosen.
To minimize pressure gradient between the left ventricle and the aorta after intraventricular rerouting, shape of the internal conduit seemed a crucial factor to be noted. Probably, turbulence occurred within the constructed channel by placement of the heart-shaped internal conduit. It was suspected that such turbulent flow was closely associated with proliferation of intimal fibrous tissues. From the technical point of view, the heart-shaped internal conduit might have been needed because of insufficient resection of the hypertrophic subaortic musculature commonly seen in this setting. Reversely speaking, Resection of the outlet septum should be extended to constract the left ventricular outflow tract as straight as possible with an oval-shaped conduit (Fig. 1), and thus progression of obstruction across the left ventricular outflow tract could be minimized. Enlargement of VSD at the time of repair would be another technical point the surgeon should pay attention to. In our present series, nonetheless, such maneuver was not needed in six, and restrictive nature of the left ventricular outflow tract was not found at the VSD level in the intermediate term. It was encouraging for us to find that the left ventricular outflow tract, if constructed with its size greater than the anticipated normal value for the aortic orifice, was not stenotic even several years after intraventricular rerouting, and that its diameter was indeed greater than that of the initially constructed channel in five of nine patients (Fig. 3). Probably, distance between the attachments of the tricuspid and the pulmonary valves can become wider in association with somatic growth. In this respect, it seems reasonable to state that the ratio of actual width of the own tissue to the circumference of the ventriculo-aortic route to be constructed should be greater than a quarter [6].
Obstruction of the right ventricular outflow tract is obviously another matter of concern. Significant pressure gradient was noted in one of the nine patients (11%) in the present series. Enlargement of the right ventricular outflow tract using a patch could have avoided progression of such obstruction. In six of nine patients (67%), a patch was placed either transannularly (in two) or for enlargement of the subpulmonary tract (in four). Of our seven patients with doubly-committed VSD in whom the internal conduit was also ready to bulge towards the right ventricle at the subpulmonary level, a transannular patch was needed in two and the right ventricular outflow tract was enlarged using a patch in another two (57%). No significant stenosis has been noted in these seven patients. Between these two groups, there was no statistical difference seen in incidence of progression of obstruction (P=0.36) or in that of enlargement of the subpulmonary portion of the right ventricle (P=0.70). In addition, of our nine patients with subpulmonary VSD and undergoing the arterial switch procedure, the right ventricle was incised to enlarge the channel from the right ventricle to the neopulmonary trunk using a patch in one (11%). In another patient, moderate obstruction of the right ventricular outflow tract was seen in the intermediate term (11%), the pressure gradient being 30 mmHg. In this group, therefore, use of a patch for enlargement of the right ventricular outflow tract was less frequent than in those undergoing the Kawashima intraventricular rerouting (P=0.016), and no statistical difference was seen in incidence of postoperative obstruction (P=1.00).
These comparisons are undoubtedly speculative because morphologic features are entirely different between these groups of patients and each entity of the malformations has its own clinical specifics. On the basis of our present results, nonetheless, intraventricular rerouting remains one of the attractive surgical options for repair in patients with double outlet right ventricle and subpulmonary VSD in terms of successful construction of the ventricular outflow tracts. Although incision to the right ventricular outflow tract seems commonly needed, with extensive resection of the subaortic masculature and optimal placement of a well-designed internal conduit, the efficiently constructed channel from the left ventricles to the aorta can last unobstructed.
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Footnotes
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Presented at the 12th Annual Meeting of the European Association for Cardio-thoracic surgery, Brussels, Belgium, September 20–23, 1998.
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References
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Received September 22, 1998;
accepted March 29, 1999.
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Abstract
1. Introduction
