Ann Thorac Surg 1995;59:473-476
© 1995 The Society of Thoracic Surgeons
A Bicuspid Pulmonary Valve Is Not a Contraindication for the Arterial Switch Operation
Hideki Uemura, MD,
Toshikatsu Yagihara, MD,
Yasunaru Kawashima, MD,
Fumio Yamamoto, MD,
Kyoichi Nishigaki, MD,
Osamu Matsuki, MD,
Tetsuro Kamiya, MD,
Siew Yen Ho, PhD,
Robert H. Anderson, MD
Department of Cardiovascular Surgery, National Cardiovascular Center, Suita, Osaka, Japan and Department of Pediatrics, National Heart & Lung Institute, London, United Kingdom
Accepted for publication October 15, 1994.
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Abstract
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There are no obvious criteria concerning the optimal repair for complete transposition with bicuspid pulmonary valve if neither the organic changes in the valve nor the pressure gradient between the left ventricle and the pulmonary trunk are severe. Instead of intraatrial switching or intraventricular rerouting in such circumstances, we have proceeded to the arterial switch procedure in 6 patients with an adequate diameter of the pulmonary valve (greater than 100% of the calculated normal aortic orifice). Postoperative catheterization (at approximately 8 months after the procedures) showed no pressure gradient between the left ventricle and the neoaorta except for a finding of 34 mm Hg difference in 1 patient who had undergone simultaneous subpulmonary myotomy. Echocardiography (7 years later in the longest follow-up) has shown no more than slight regurgitation across the bicuspid neoaortic valve, with no progressive increase of blood velocity across the valve. From these results in the middle term, we conclude that the arterial switch procedure remains an option of choice for patients with initially bicuspid pulmonary valve, providing there is no severe subpulmonary stenosis.
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Introduction
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The superiority of the arterial switch operation over other procedures such as intraatrial switching as the definitive repair for complete transposition (concordant atrioventricular and discordant ventriculo-arterial connections) has been established [1–5]. Severe organic obstruction of the left ventricular outflow tract or major organic changes in the pulmonary valve itself, however, are still considered to be contraindications for the arterial switch operation, pointing the surgeon toward other surgical options [6–8]. As yet, the position of the pulmonary valve with two leaflets in this decision-making process remains uncertain. A few patients have undergone the arterial switch with bicuspid pulmonary valves in the absence of organic changes in the leaflets and when the pressure gradient between left ventricle and pulmonary trunk was no more than moderate [9–11]. Encouraged by these limited reports, we proceeded to the arterial switch procedure when the diameter of a bicuspid pulmonary valve was deemed sufficiently large. Our experience with 6 such patients is described herein.
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Material and Methods
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Patients
Six patients having complete transposition with a bicuspid pulmonary valve have thus far undergone the arterial switch operation at the National Cardiovascular Center in Osaka, Japan (Fig 1
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Fig 1. . Preoperative profiles of patients showing morphologic and physiologic data derived from preoperative and perioperative examinations. (* 1 = classification by Shaher and colleagues [12]; *2 = systemic-to-pulmonary shunt and banding of the pulmonary trunk; *3 = pressure gradient between the left ventricle and the pulmonary arteries; *4 = percent of normal aortic valvar orificial diameter (nAVD) calculated from body surface area (BSA) as nAVD (mm) = 16.6 x BSA0.60 [13]; *5 = diameter of left ventricular outflow tract was 85% of nAVD in patient 1 and 88% in patient 6; Qp/Qs = ratio of pulmonary to systemic blood flow.)
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The preoperative diameter of the pulmonary valve, measured angiographically in each patient, ranged from 104% to 142% (mean, 124% ± 17%) of the expected normal aortic orificial diameter calculated from body surface area [13]. One end of the commissure between the leaflets was facing the aorta in 4 patients, whereas it was transverse in 2 patients. Minimal fusion of leaflets was recognized in 1 patient, and coexisting mild subpulmonary stenosis in another 2 patients. There were two patterns of coronary arterial orifices. In 5 patients, a main stem supplying the anterior interventricular artery and the circumflex artery arose from the left-hand facing sinus (sinus 1) and the right coronary artery from the right-hand facing sinus (sinus 2), with facing sinuses viewed from the perspective of the pulmonary trunk looking toward the aorta. In the other patient, only the anterior interventricular artery arose from the left-hand facing sinus (sinus 1) whereas the right coronary artery and the circumflex artery arose from a common stem in the right-hand facing sinus (sinus 2). A ventricular septal defect was present in all 6 patients.
The preoperative pressure gradient between the left ventricle and the pulmonary arteries was 39 ± 7 mm Hg except in 2 patients who had undergone previous banding of the pulmonary trunk (58 and 92 mm Hg).
Procedures
The arterial switch procedure was performed on patients aged 18 days to 2.9 years, using the maneuver in which the switched ascending aorta is placed posteriorly to the bifurcation of the pulmonary trunk [7]. The coronary arteries were translocated to punched-out holes within the tubular portion of the neoaortic root. The ventricular septal defects were closed transatrially. Pulmonary commissurotomy was performed in the patient who had minimal fusion of leaflets (patient 2), whereas subpulmonary myotomy was carried out in the 2 patients with mild subpulmonary stenosis (patients 1 and 6).
The pressure gradient between the left ventricle and the pulmonary arteries was measured immediately after the repair in the operating room and at postoperative catheterization at a mean of 8 months after the operation. Sequential echocardiography was performed postoperatively to check both the competence of the neoaortic valve and the velocity of blood across the valve (Table 1).
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Results
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There were no operative deaths, but there was one late death. Patient 3 died suddenly 2 months after the operation, probably due to a coronary arterial problem. The other 5 patients are alive and asymptomatic from 8 to 87 months after repair (see Table 1
). Measurement of pressures immediately after the repair and at the postoperative catheterizations revealed differences of 11 ± 7 mm Hg and 9 ± 13 mm Hg between the left ventricle and the neoaorta, respectively (Fig 2). Patient 1, who showed a pressure difference of 34 mm Hg at rest, was also examined under isoproterenol loading, which increased the pressure gradient to 78 mm Hg. The sequential postoperative echocardiograms have shown no more than slight regurgitation across the neoaortic valve (see Table 1), with no progressive increase in velocity of blood across the valve (Fig 3).
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Fig 2. . Pressure gradient across the left ventricular outflow tract. No significant pressure difference was detected between the left ventricle and the aorta after the arterial switch procedure except in patient 1. The pressure gradient in this patient was enhanced to 78 mm Hg by loading isoproterenol. (*1 = pressure difference between the left ventricle and the pulmonary arteries; *2 = pressure difference between the left ventricle and the aorta; *3 = after banding of the pulmonary trunk.)
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Fig 3. . Flow velocity across the bicuspid neoaortic valve. Sequential echocardiographic studies have demonstrated no significant progression of velocity of flow.
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Comment
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The arterial switch procedure is now recognized as the procedure of choice for patients with complete transposition [1–4]. The morphologically left ventricle is restored to the role of the systemic ventricle after the operation, avoiding the necessity for the morphologically right ventricle to continue in a role to which it is almost certainly unsuited [4, 5, 14] and the role in which it is required to function after the atrial switch procedure. Other unfavorable long-term sequelae after atrial redirection procedures, such as atrial arrhythmias or obstructions in the venous pathways, are unlikely to happen with any frequency in patients who have been treated by the arterial switch procedure [4]. As for the options of intraventricular repair, the superiority of the arterial switch is based on the fact that neither right ventriculotomy nor insertion of conduits is usually necessary with the arterial option. An additional merit of the arterial switch procedure is that it permits definitive repair during neonatal life or early infancy, thus avoiding the development of either pulmonary vascular disease or the deleterious effects of cyanosis on the systemic organs. The procedure does, nonetheless, result in a potential problem concerning the long-term function of the neoaortic valve which is, anatomically, initially a pulmonary valve [11, 15]. Such concern, particularly with regard to progressive obstruction or regurgitation, is magnified when the pulmonary valve itself was initially bicuspid [9–11].
Despite this potential caveat, recognizing the overwhelming superiority of the arterial switch procedure over its alternatives and the minimal problems likely to occur after the procedure, we decided to employ the arterial switch option in those patients referred to our center with bicuspid pulmonary valves having an orifice larger than that expected for the normal aorta and lacking any severe organic changes in the leaflets. Thus far, the results in the middle term justify our decision. Neither progressive obstruction nor regurgitation of the neoaortic valve has been recognized after the operation. Presumably, minimal fusion of the leaflets, such as that treated by commissurotomy in patient 2, has had little or no consequence.
The morphologic criteria supporting our surgical strategy were based on two considerations. The first is the fact that a valve corresponding in size to that of the anticipated aortic orifice for a patient of comparable body surface area should be sufficient to sustain the systemic flow crossing the neoaortic valve after anatomic repair. The other reason is that, in our opinion, the preoperative pressure gradient between the left ventricle and the pulmonary arteries does not necessarily represent the severity of obstruction of the left ventricular outflow tract to be found after the repair, because the flow of blood through the tract is pathophysiologically abnormal before definitive repair. Additionally, as is often documented in the setting of complete transposition with intact ventricular septum, so-called dynamic obstruction is frequently responsible for producing pressure gradients across the left ventricular outflow tract [16]. These disappear after the normalization of the circulation by the arterial switch procedure.
From the technical stance, we emphasize other morphologic features. In our only patient who died late (patient 3), angiography performed as an emergency just before the death revealed a patent but narrowed main trunk of the left coronary artery with a high take-off from the neoaorta. Our preference when translocating the coronary arteries has been to follow the technique proposed by Yasui and colleagues [17] in which the coronary arterial buttons are anastomosed to the neoaortic root above the level of the hinge points of the leaflets so as to diminish the postoperative potential for neoaortic valvar insufficiency. Although we had not recognized any difficulties in translocation of the coronary artery in this fashion at the time of operation, we now speculate that the direction of the commissure between the two leaflets of the initial pulmonary valve, at right angles to the commissure between the facing aortic leaflets, might have restricted the potential site of anastomosis between the coronary arterial buttons and the neoaorta. Some additional options [18, 19] could probably be considered for future treatment of such patients with commissural mismatch.
The role of coexisting subpulmonary stenosis, when due to posterior deviation of the outlet septum with a so-called ``malalignment ventricular septal defect'' in the setting of complete transposition [15, 20, 21], seems controversial. As is often the case with tetralogy of Fallot, bicuspid pulmonary valves may be observed in such hearts with deviation of the outlet septum into the subpulmonary outflow tract [22]. Fortunately, in our series, the deviation of the outlet septum was minimal. In the postmortem specimens at the National Heart & Lung Institute in London, however, three hearts out of four with complete transposition and bicuspid pulmonary valves had marked posterior deviation of the outlet septum. Such malalignment will nowadays be readily demonstrated preoperatively by either echocardiography or angiography. Needless to say, the severity of such stenosis will reflect the chosen surgical repair [21]. If an adequate diameter of the left ventricular outflow tract is not obtained by myotomy of the ventricular septum or partial resection or incision of the deviated outlet septum, then either a Rastelli-type operation [6], its modification [7], or the procedure devised by Nikaidoh [8] offers alternative surgical choices. The more markedly the outlet septum is posteriorly deviated, the easier can the pathway be created without obstruction from the left ventricle to the aorta by these alternative procedures. The patients with subpulmonary stenosis in this study, patients 1 and 6, had the smallest diameters of left ventricular outflow tracts in our series, measuring 85% and 88% of anticipated normal aortic orificial diameters, respectively. They were considered suitable for treatment not by an extensive resection of the outlet septum but rather by a limited incision within it. Although we do not regard the presence of a residual 34-mm Hg pressure difference between the left ventricle and the neoaorta in patient 1 as a critical problem for the present, we will follow up this patient carefully, judging the significance of any increase in pressure gradient by use of the loading test with isoproterenol.
It is obviously necessary to continue to investigate our patients over a much longer term, because aortic valvar stenosis in the setting of a bicuspid valve in an otherwise normally structured heart does not usually become of major clinical importance until later life. Nonetheless, our results in the middle term support the notion that the arterial switch remains a good option for patients with complete transposition and coexisting bicuspid pulmonary valve.
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Footnotes
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Address reprint requests to Dr Uemura, Department of Pediatrics, National Heart & Lung Institute, Dovehouse St, London SW3 6LY, United Kingdom.
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References
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Abstract
Introduction
