Neonatal arterial switch operation: coronary artery patterns and coronary events 1

European Journal of Cardio-thoracic Surgery 11 (1997) 810 817 Neonatal arterial switch operation: coronary artery patterns and coronary events 1 Daniel Tamisier, Ruth Ouaknine, Philippe Pouard, Philippe Mauriat, Didier Lefebvre, Daniel Sidi, Pascal R. Vouhé * Department of Cardiac Surgery, Laënnec Hospital 42, rue de Sè res, 75340 Paris Cédex 07, France Received 8 October 1996; received in revised form 22 January 1997; accepted 22 January 1997 Abstract Objective: To determine the incidence of coronary events following neonatal arterial switch and to identify potential risk factors for death and coronary events. Methods: The total experience (236 consecutive arterial switch operations) of one surgeon was studied. Associated procedures included ventricular septal defect closure in 37 patients (16%) and aortic arch repair in 14 patients (6%). The influence of various patient, procedural, support technique and experience variables was analyzed. Results: There were 19 deaths (8 70% confidence limits=6 10%). Survival at 1 month, 1 year and 5 years was 93, 92 and 92%, respectively. Risk factors for death included small birth weight (P=0.0015), hypoplasia of right ventricle (P 0.0001), aortic arch obstruction (P 0.0001) and coronary patterns with coronary arteries coursing between the great arteries (P=0.0066). Coronary events occurred in 26 patients (11 70% confidence limits=9 13%) and involved coronary deaths (11 patients), non fatal myocardial infarctions (8 patients) and coronary stenoses or occlusions (7 patients). Freedom from coronary events at 1 month, 1 year and 5 years was 94, 91 and 88% respectively. Risk factors for coronary events included coronary patterns with retropulmonary course of the left main or left circumflex coronary artery (P=0.0122), coronary patterns with coronary arteries coursing between the great arteries (P 0.0001), all variations of intramural coronary arteries (P=0.0010) and commissural origin of coronary ostia (P=0.0171). Conclusions: (1) In most neonates, arterial switch operation carries a low operative risk and provides excellent mid-term results; (2) The operative risk remains increased in some subsets; and (3) Some coronary patterns increase the risk of coronary events. Further surgical experience may improve the results. 1997 Elsevier Science B.V. Keywords: Arterial switch operation; Neonates; Mortality; Coronary events 1. Introduction In the past decade, the arterial switch operation (ASO) has become the preferred surgical procedure for transposition of the great arteries (TGA) in neonates. This operation is performed with a low mortality rate in many institutions. Successful transfer * Corresponding author. Tel.: +33 1 44396505; fax: +33 1 44396520. 1 Presented at the 10th Annual Meeting of the European Association for Cardio-thoracic Surgery, Prague, Czech Republic, 6 9 October, 1996. of the coronary arteries to the neoaorta represents the key-point of the procedure. The difficulty of this surgical step is greatly influenced by the variable coronary anatomy noted in patients with TGA. Coronary complications remain the main cause of mortality and morbidity following ASO. The present report describes the total experience of one surgeon with neonatal ASO, including the initial learning curve period. The causes and risk factors of early and late mortality were studied. The incidence of coronary events was evaluated. The results were examined to determine whether some coronary patterns were associated with increased mortality and morbidity. 1010-7940/97/$17.00 1997 Elsevier Science B.V. All rights reserved. PII S1010-7940(97)01178-0

D. Tamisier et al. / European Journal of Cardio-thoracic Surgery 11 (1997) 810 817 811 Table 1 Associated cardiovascular anomalies Cardiovascular anomaly No. % Total deaths No % CL (%) Coarctation 7 3.0 4 57 32 79 Interrupted aortic arch 1 0.4 0 0 0 85 Hypoplastic transverse arch 14 5.9 5 36 19 53 Hypoplastic right ventricle 7 3.0 4 57 32 79 Multiplicity of VSD (in VSD group) 5 2.1 1 20 3 52 LVOT anomalies 5 2.1 1 20 3 52 Bicuspid pulmonary valve 7 3.0 2 29 10 55 Situs inversus 1 0.4 1 100 15 100 CL, 70% confidence limits; VSD, ventricular septal defect; LVOT, left ventricular outflow tract. 2. Materials and methods 2.1. Study group The last author of this paper performed his first neonatal arterial switch in January 1987. Between January 1987 and July 1995, he then performed 236 consecutive operations. During the same period, three neonates, referred for arterial switch, underwent Senning operation because of unfavorable coronary anatomy. A total of 199 patients (84%) had TGA with essentially intact ventricular septum (20 of them had an hemodynamically insignificant VSD), 37 patients (16%) had TGA with VSD. The age at the time of operation varied from 1 to 29 days (mean S.D.=8 5 days) and the weight from 2.0 to 4.6 kg (mean S.D.=3.3 0.5 kg). In all, 182 patients (77%) underwent preoperative balloon atrial septostomy and 168 (71%) received an infusion of prostaglandin. Associated cardiovascular anomalies are listed in Table 1. Most commonly (172/236-73%), the aorta was directly anterior to the pulmonary artery. In 47 patients (20%) the aorta was more or less to the right of the pulmonary artery and the great arteries were side-byside in 17 patients (7%). Coronary artery patterns were determined from the operative descriptions. In agreement with Serraf et al., the coronary patterns were grouped into three main types [10]. This classification takes into account the origin and the initial course of the coronary arteries, which are the main determinants for the mechanisms of myocardial ischemia after relocation. Table 2 shows the coronary artery distribution according to this surgical classification. 2.2. Operation All operations were performed under hypothermic cardiopulmonary bypass, including a period (mean=26 min) of hypothermic total circulatory arrest for aortic arch repair if needed (14 patients). Mean ( S.D.) ischemic time was 80 12 min (60 135 min). The methods of myocardial preservation varied with the time. The first 28 patients underwent multidose cristalloid cardioplegia. The following 195 had multidose blood cardioplegia followed by warm reperfusion, whereas, in the last 13 patients, hot cardioplegic induction was added to the preservation technique. Ultrafiltration was routinely used during the rewarming period. In one patient (0.4%), the arterial switch was performed without coronary artery transfer, according to the technique described by Moat et al. [8]. In all the other patients, the coronary ostia were excised from the aortic sinuses and transferred to the neoaortic root, using the various accepted techniques. However, between patient number 121 and patient number 174, an original technique, involving reimplantation of both coronary ostia side by side after excision of a single button of neoaortic wall, was routinely used [11]. In nine cases, coronary anastomoses had to be revised at the end of the procedure because of inadequate myocardial perfusion. In one of these cases, the myocardial perfusion of an intramural left anterior descending (LAD) artery remaining inadequate despite revision, the left mammary artery was anastomosed to the LAD; the postoperative course was uneventful and the mammary to LAD anastomosis was patent at angiography performed 2 months after surgery. The Lecompte maneuver was used in all patients. The coronary artery donor sites were routinely patched with a fresh pantaloon piece of autologous native pericardium and 27 patients (11%) underwent delayed sternal closure. 2.3. Follow-up Follow-up data (100% complete) were obtained during a 1 month interval closing on August 1, 1995.

812 D. Tamisier et al. / European Journal of Cardio-thoracic Surgery 11 (1997) 810 817 Table 2 Coronary artery distribution Coronary pattern No. % Total deaths No % CL (%) Two ostia from posterior facing sinuses and normal course of right and 160 68 left coronary arteries ( usual coronary pattern) 9 6 4 8 One or two ostia arising from one or two facing sinuses, but either one artery 59 25 5 8 5 14 (RCA) loops in front of aorta, or one artery (LCA or Cx) loops posterior to pulmonary artery, or two arteries loop around the great arteries One or two ostia arising from one or two facing sinuses, but one or both 17 7 5 29 17 44 arteries course between the great arteries 236 19 8 6 10 CL, 70% confidence limits; RCA, right coronary artery; LCA, left coronary artery; Cx, left circumflex artery. Children not followed up at this institution were contacted through referring physicians. Among the 217 survivors, the mean ( S.D.) follow-up was 39 27 months (range 1 102 months). Routine follow-up evaluation included clinical, electrocardiographic, echocardiographic and Doppler studies. Coronary angiography was not performed routinely but was undertaken in the presence of electrocardiographic and/or echocardiographic abnormalities, in patients in whom coronary transfer had been surgically difficult and in most patients who underwent coronary transfer using the side-by-side reimplantation technique. A total of 95 patients underwent coronary angiography at intervals of from 1 to 40 months (mean=10 5 months). 2.4. Data analysis Continuous data were presented as means 1 S.D. and crude ratios with 70% confidence limits. Time-related events were examined using the Kaplan Meier actuarial method. Univariate analysis was used to evaluate the influence of various patient, procedural, support technique and experience variables (Appendix A). Analysis was done using the 2 method and Fisher s exact test when cells had expected values 5. Statistical significance was established at P=0.05. causes of the 8 non coronary-related deaths were as follows: hypoplastic right ventricle [3], SVC thrombosis [2], mediastinitis [1], irreversible pulmonary hypertension [1], sudden death (presumably from arrhythmia) [1]. Risk factors found to be associated with an increased mortality are listed in Table 3. Strong incremental risk factors for death were low birth weight, right ventricular outflow tract obstruction (hypoplastic right ventricle andlor aortic arch obstruction) and coronary patterns with coronary arteries coursing between the great arteries (Table 1 and Table 2). Birth weight was 2.9 0.4 kg in patients who died and 3.3 0.5 kg in the survivors (P=0.0015). Hypoplasia of the right ventricle, a strong incremental risk factor, was considered present when the diameter of the tricuspid valve was less than 75% of the diameter of the mitral valve; 6 of the 7 patients with hypoplasia of the right ventricle had concommittant aortic arch obstruction. Earlier date of operation was not a risk factor although there was an increased mortality during the first 2 years (Table 4). The mortality rate among patients with TGA/intact septum without aortic arch obstruction was 6% (70% 3. Results 3.1. Sur i al Survivals at 1 month, 1 year and 5 years were 93, 92 and 92%, respectively (Fig. 1). In all, 19 patients died; 16 of them died before discharge from the hospital and 3 within 3 months after surgery; there were no deaths beyond 3 months. Of the deaths, 11 (58%) (8/16 early deaths, 3/3 late deaths) were coronary-related. The Fig. 1. Actuarial survival.

D. Tamisier et al. / European Journal of Cardio-thoracic Surgery 11 (1997) 810 817 813 Table 3 Risk factors for death at any time after repair Incremental risk factors for death P value Patient variables Demographic Low birth weight 0.0015 Morphologic Hypoplastic right ventricle 0.0001 Hypoplastic transverse arch 0.0001 Aortic coarctation 0.0001 Coronary arteries between great arteries 0.0066 Intramural coronary arteries 0.0136 Procedure variable Aortic arch repair 0.0249 Support variables Total circulatory arrest 0.0086 Delayed sternal closure 0.0122 CL=4% 8%) and it was 10% (70% CL=5% 19%) in those with TGA/VSD without arch obstruction. The mortality rate was increased up to 36% (70% CL = 21% 53%) in patients with aortic arch obstruction (with or without VSD). 3.2. Coronary e ents Coronary events occurred in 26 patients and included coronary-related deaths (11 patients), non fatal myocardial infarctions (8 patients) and coronary stenoses or occlusions (7 patients). Six of the eight patients who sustained postoperative myocardial infarction had a normal left ventricular function at last follow-up (one of them with a residual mild mitral regurgitation); the last 2 patients had global left ventricular dilation and hypokinesia. Coronary artery lesions without myocardial infarction were suspected on echocardiographic (3 patients) or radioisotopic (2 patients) abnormalities and Table 4 Number of arterial switch operations and mortality in each year of this study Year No. Total deaths No % CL (%) 1987 13 2 15 5 32 1988 13 3 23 11 41 1989 9 0 0 0 18 1990 35 2 6 2 13 1991 26 2 8 3 17 1992 42 7 17 11 24 1993 30 0 0 0 6 1994 46 3 7 3 13 Early 1995 22 0 0 0 8 236 19 8 6 10 CL, 70% confidence limits. Fig. 2. Actuarial freedom from coronary events. confirmed at coronary angiography; in 2 patients, coronary stenoses were asymptomatic and were found at routine coronary angiography. Freedom from coronary events at 1 month, 1 year and 5 years was 94, 91 and 88%, respectively (Fig. 2). The incidence of coronary complications was significantly influenced by the coronary anatomy (Table 5). Detailed analysis of coronary anatomy showed that the risk of coronary events was increased in patterns with retropulmonary course of the left circumflex or left common coronary artery (P=0.0122), in all variations of intramural coronary arteries (P=0.0010) and in patterns with commissural origin of one or both coronary ostia (P=0.0171). Patterns with coronary arteries coursing anterior to the aorta (P=0.3150) and patterns with all coronary arteries arising from one single sinus (P=0. 1900) were not significant risk factors. The techniques of coronary relocation did not influence significantly the incidence of coronary events. However, the influence of the side-by-side technique of reimplantation, which was used routinely for several months, was carefully studied. The side-by-side reimplantation technique was compared to the other accepted techniques of coronary transfer. The results are shown in Table 6. Although no difference reached statistical significance, the side-by-side technique of coronary reimplantation was associated with an increased incidence of coronary events in coronary patterns involving coronary arteries looping around the great arteries. 3.3. Reoperations Of the 13 patients who underwent reoperation, 1 died. Freedom from reoperation at 1 month, 1 year and 5 years was 99, 98 and 92%, respectively (Fig. 3). Seven patients (3% of survivors 70% CL=2% 5%) underwent reoperation for supravalvar pulmonary stenosis 4 80 months (mean 34 months) after the initial

814 D. Tamisier et al. / European Journal of Cardio-thoracic Surgery 11 (1997) 810 817 Table 5 Coronary artery patterns and incidence of coronary events Coronary pattern No. Coronary events No % CL (%) Usual pattern 160 8 5 3 7 Patterns with arteries posterior to pulmonary artery and/or anterior to aorta 59 11 19 13 45 Patterns with arteries between great arteries 17 7 41 27 56 P 0.0001 CL, 70% confidence limits. 236 26 11 9 13 operation. In 3 patients with simple TGA, neoaortic coarctation developed after the arterial switch operation; coarctation repair was performed 3, 5 and 26 months after initial surgery. Three patients had reintervention for coronary problems. One patient had postoperative myocardial infarction due to severe stenosis of the right coronary artery; he underwent reoperation 23 days after the arterial switch and died in the operating room. Two patients with severe stenosis of the left coronary artery underwent surgical angioplasty of the left main artery 30 months and 7.5 years after the arterial switch with satisfactory mid-term angiographic results. 4. Discussion Many reports have shown that the arterial switch operation carries an acceptably low operative risk and provides very satisfactory mid-term results in neonates with TGA, with or without associated ventricular septal defect [6,7,10,12]. In most series, a learning curve effect was demonstrated; this is also the case in this report regarding the overall experience of one surgeon. Although the mortality rate of ASO is approaching zero in most neonates with TGA, there remain some situations in which the operative risk is higher. Open heart surgery under cardiopulmonary bypass still carries increased mortality and morbidity rates in neonates with a low birth weight. Aortic arch obstruction (interrupted aortic arch, hypoplastic transverse arch with or without aortic coarctation) is associated with an increased risk following ASO [6]. This is particularly the case when there is concommittant hypoplasia of the right ventricle. Although this is a rare situation (3% in the present series), it remains difficult to determine, in the neonate, which right ventricle is too small to sustain the pulmonary circulation. In the light of the poor outcome following neonatal ASO in this subgroup of patients, a surgical program leading to a one and half ventricle repair or a Fontan-type repair beyond the neonatal period may be a superior management option. Since the introduction of the arterial switch operation, it has been obvious that adequate transfer of the coronary ostia from the anterior aortic orifice to the posterior neoaortic orifice was the surgical key-point of the procedure. Coronary complications are responsible for most of deaths following ASO; in the present study, this was the case in 50% of early deaths and in all late deaths. There is also a significant incidence of coronary morbidity. Coronary complications are easy to detect when there is an evident postoperative myocardial infarction with electrocardiographic and echocardiographic sequelae. Sometimes, the anomalies are more subtle with minor electrocardiographic or echocardiographic changes (such as mild segmental wall motion abnormality or mild mitral insufficiency). There are also coronary stenoses or occlusions without clinically detectable myocardial consequences, probably owing to an adequate collateral circulation between the patent coronary artery and the stenosed or occluded one. These asymptomatic coronary lesions can be detected only by systematic coronary angiography. In the present study, coronary angiography was not performed routinely but only in selected patients (minor electrocardiographic or echocardiographic changes, operative difficulties in coronary transfer, patients undergoing coronary reimplantation by the side-by-side technique because a higher incidence of coronary events was suspected). Therefore, the accurate incidence of coronary complications was probably underestimated. To obviate this drawback, this is our current policy to perform routine coronary angiography 1 year after arterial switch operation. The variability of coronary anatomy in patients with TGA was mainly of academic interest for a long time but became of critical importance with the introduction of the arterial switch operation. Several classifications have been reported to provide adequate description of the various coronary patterns. All these classifications may be useful to provide detailed morphologic description of the anatomy. However, in agreement with the Marie Lannelongue group, we believe that, from a purely surgical point of view, a distribution of the various coronary patterns into three groups, is optimal in the surgical decision making. In the first group (usual coronary pattern), there are two coronary ostia arising from the posterior facing sinuses and the right and left

D. Tamisier et al. / European Journal of Cardio-thoracic Surgery 11 (1997) 810 817 815 Table 6 Incidence of coronary events accordinq to coronary patterns and techniques of coronary relocation Coronary pattern Side-by-side technique All accepted techniques Usual pattern 6 (2 12) 5 (3 8) Patterns with arteries posterior to pulmonary artery and/or anterior to aorta 36 (19 53) 13 (8 20) Patterns with arteries between great arteries 33 (12 62) 45 (28 64) 16 (11 23) 9 (7 13) The incidence of coronary events is expressed in % with 70% confidence limits. coronary arteries have a normal initial course; coronary transfer can usually be performed with a minimal risk of deformation. In the second group (7 subtypes), there are one or two ostia arising from one or two facing sinuses but either one artery (usually the right coronary artery) loops in front of the aorta, or one artery (left coronary artery or left circumflex artery) loops posterior to the pulmonary artery, or two coronary arteries loop around the great arteries; coronary transfer carries an increased risk of stretching or kinking of the coronary vessels. In the third group (five subtypes), there are one or two ostia arising from one or two facing sinuses, but one or both arteries course between the great arteries; coronary relocation carries a high risk of coronary torsion, more especially as the frequent association of an intramural course or a commissural origin adds to the surgical difficulty of coronary transfer. Several reports have clearly established that some coronary patterns are associated with an increased incidence of deaths and coronary events [3,6,7,10,12]. In some series [6,12], coronary patterns with coronary arteries looping posterior to the pulmonary artery are associated with an increased mortality rate. In the present series, a retropulmonary course of left main or left circumflex artery did not influence the mortality rate but was associated with an increased incidence of coronary events. This was particularly the case when the side-by-side technique of coronary reimplantation Fig. 3. Actuarial freedom from reoperation. is used (Table 6). The routine use of this surgical technique has been discouraged, particularly in these coronary patterns [2]. In agreement with the other reported series, coronary patterns with coronary arteries coursing between the great arteries (including most patterns with intramural course or commissural origin) were associated with an increased incidence of mortality and coronary events. Increasing experience and innovative techniques may however lessen this risk [1]. The first 6 patients of the present series who had such patterns, all had coronary complications with 5 deaths. In the following 11 patients, there was only one coronary event, which finally had a favorable outcome owing to an immediate mammary to LAD anastomosis. Because of the increased risk of coronary complications in this group of patients and since it is possible to detect coronary arteries coursing between the great arteries on preoperative echocardiography, the question arises to know whether such patients should undergo Senning procedure instead of ASO. However, the known risk of sudden death in patients with the left coronary artery coursing between the aorta and the pulmonary trunk [9], provides a strong argument to perform ASO in all neonates with TGA, whatever the coronary anatomy. Coronary events must be prevented by a perfect coronary transfer at the time of ASO. After unclamping of the aorta, the adequacy of myocardial perfusion must be ascertained. Any abnormality in myocardial performance is strongly suggestive of a coronary perfusion problem. Should this be the case, the cause must be clearly identified at this moment and aggressively corrected by revision of the coronary anastomoses. In desperate situations, performing a mammary to coronary artery bypass may be a life-saving procedure [4,5]. The optimal management of postoperative coronary lesions remains to be determined. Our current policy is to perform surgical revascularization when radioisotopic and positron emission tomographic data show the presence of ischemic viable myocardium. Thus, 2 patients with severe stenosis of the left coronary artery underwent successful surgical angioplasty of the left main artery.

816 D. Tamisier et al. / European Journal of Cardio-thoracic Surgery 11 (1997) 810 817 Acknowledgements We gratefully acknowledge the secretarial assistance of Miss Corinne Pasquet. References [1] Asou T, Karl TR, Pawade A, Mee RBB. Arterial switch: translocation of the intramural coronary artery. Ann Thorac Surg 1994;57:461 465. [2] Bonnet B, Bonhoeffer P, Piéchaud JF, Stümper O, Kachaner J, Sidi D, Vouhé PR. Coronary obstructions after reimplantation of the two coronary ostia in a single orifice during arterial switch operation for transposition of the great arteries. Eur J Cardio-Thorac Surg 1996;10:482. [3] Day RW, Laks H, Drinkwater DC. The influence of coronary anatomy on the arterial switch operation in neonates. J Thorac Cardiovasc Surg 1992;104:706 712. [4] Ebels T, Merzelaar K, Gallandat-Huet RCG, Bink-Boelkens MTE, Cromme-Dijkhuis A, Bams JL, Boeve WJ, Eijglaar A. Neonatal arterial switch operation complicated by intramural left coronary artery and treated by left internal mammary bypass. J Thorac Cardiovasc Surg 1989;97:473 475. [5] Grabitz RG, Messmer BJ, Seghaye MC, Engelhardt W, Mueller E, Von Bermuth G. Internal mammary artery bypass graft for impaired coronary perfusion after neonatal arterial switch operation. Eur J Cardio-Thorac Surg 1992;6:388 390. [6] Kirklin JW, Blackstone EH, Tchervenko CI, Castaneda AR. Clinical outcomes after the arterial switch operation for transposition. Patient, support, procedural, and institutional risk factors. Circulation 1992;86:1501 1515. [7] Mayer JE Jr, Sanders SP, Jonas RA, Castaneda AR, Wernovsky G. Coronary artery pattern and outcome of arterial switch operation for transposition of the great arteries. Circulation 1990;82(Suppl IV):IV;139 145. [8] Moat NE, Pawade A, Lamb RK. Complex coronary arterial anatomy in transposition of the great arteries. Arterial switch procedure without coronary relocation. J Thorac Cardiovasc Surg 1992;103:872 876. [9] Mustafa l, Gula G, Radley-Smith R, Durrer S, Yacoub M. Anomalous origin of the left coronary artery from the anterior aortic sinus: a potential cause of sudden death. Anatomic characterization and surgical treatment. J Thorac Cardiovasc Surg 1981;82:297 300. [10] Serraf A, Lacour-Gayet F, Bruniaux J, Touchot A, Losay J, Comas J, Sousa Uva M, Planché C. Anatomic correction of transposition of the great arteries in neonates. J Am Coll Cardiol 1993;22:193 200. [11] Vouhé PR, Haydar A, Ouaknine R, Albanese SB, Mauriat Ph, Pouard Ph, Tamisier D, Leca F. Arterial switch operation: a new technique of coronary transfer. Eur J Cardio-Thorac Surg 1994;8:74 78. [12] Wernovsky G, Mayer JE Jr, Jonas RA, Hanley FL, Blackstone EH, KirkIin JW, Castaneda AR. Factors influencing early and late outcome of the arterial switch operation for transposition of the great arteries. J Thorac Cardiovasc Surg 1995;109:289 302. Appendix A. Variables entered into the univariate analysis Patient variables: (1) Demography: sex, age at operation (days), birth weight (kg). (2) Preoperative variables: atrial septostomy, prostaglandin infusion, neonatal infection. (3) Cardiac morphology: type of TGA (simple versus TGA with VSD), multiplicity of VSDs, right ventricular outflow tract obstruction (defined as coexisting hypoplastic right ventricle and/or subaortic stenosis and/or coarctation and/or hypoplastic arch and/or interrupted arch), left ventricular outflow tract obstruction, position of the great arteries. (4) Coronary artery patterns: grouped patterns ([10]) and isolated patterns: (a) patterns with a retropulmonary course of coronary arteries; (b) patterns with a coronary course in front of aorta; (c) all coronary arteries arising from one single sinus; (d) all variations of intramural coronary arteries; and (e) commissural origin of one or both coronary ostia. Procedural variables: VSD closure, aortic arch repair, technique of coronary reimplantation, revision of coronary anastomosis, delayed sternal closure. Support technique variables: Use and duration of circulatory arrest, global myocardial ischemic time. Experience variable: Sequence number of arterial switch. Appendix B. Conference Discussions Dr S. Conte (Copenhagen, Denmark): This was a very interesting study and I would like to congratulate you for the excellent results. I have two brief questions. The first is related to patients with small birth weight, major risk factor for death in your series, or with preoperative conditions. As in most of them the ventricular septum is intact, don t you think that delaying surgery beyond the normal neonatal period, to a time when the preoperative conditions are improved, with subsequent use of the rapid two-stage approach, may be a safer option in some of these patients? Furthermore, I would like to know if any of the patients of your series who survived coronary events subsequently underwent coronary revascularization, and how are they actually doing? Dr P.R. Vouhé: In answer to your first question, a rapid two-stage arterial switch is indicated in infants reaching the hospital beyond the neonatal period with a left ventricle considered as unable to sustain the systemic circulation. Regarding the second question, two patients with stenosis of the left main coronary artery underwent surgical angiopiasty with satisfactory mid term angiographic results. Dr F. Lacour-Gayet (Paris, France): I would like to congratulate Pascal for his beautiful presentation and make a comment on the coronary occlusions. So far, on a series of 850 switch is surviving, we have reoperated two patients with coronary occlusion and another patient is waiting for reoperation. The three patients who were diagnosed with coronary occlusion had a lesion that was directly related to the surgical technique. The patients that have been checked by angiography were the patients done early in our experience, before 89, and it is expected that with time, the surgical technique has improved and we believe that these events can be certainly limited. Now, my question regards your experience with two-stage switch. It has been very clear in Paris, at Marie-Lannelongue, that since we

D. Tamisier et al. / European Journal of Cardio-thoracic Surgery 11 (1997) 810 817 817 have decided not to operate early some patients that present with preoperative damages, namely renal insufficiency, neurologic disorders, and multiorgan failure, the morbidity and the mortality has decreased. We will now, delay the operation until the preoperative damages are ruled out and perform a two-stage switch after reconditioning the left ventricle. In our experience, preoperative damages has been a significant critical risk for early mortality. I would like to ask you if you have had a similar experience? Dr P.R. Vouhé: No, we did not delay surgery in neonates with extracardiac damages, to the point of requiring a two-stage operation. But, I agree that your approach is probably safe and recommendable. Dr T. Karl (Melbourne, Australia): Thank you for that excellent presentation, Pascal. I m interested to know how we can diagnose myocardial infarction and other coronary events in the early postoperative period. Is it always possible to separate this problem from myocardial dysfunction related to a deconditioned left ventricle and so forth? I ask because in our own practice we have had many very sick infants in whom we suspected a coronary problem and in whom complete recovery was seen, with a normal electrocardiogram, only a few days afterward. Could you comment on how you made the diagnosis in your own patients? Dr P.R. Vouhé: We had the same experience. It is difficult, in a patient with postoperative left ventricular dysfunction, to determine the exact cause of that dysfunction. Some signs are particularly suggestive of coronary problems, such as segmental wall motion anomalies, EKG abnormalities or mitral insufficiency The fact that left ventricular function recovers is not necessarily the proof that there is no coronary problem; this may be the sign that collateral circulation developps between the patent coronary artery and the occluded one. The only way to diagnose coronary problems and to determine the exact incidence of coronary complications is to perform coronary angiography not only in patients with symptoms suggestive of coronary ischemia, but also on a routine basis. Mr D. Anderson (London, England): You mentioned mammary artery bypass to the left coronary in difficult situations. Are you able to tell us how often you have had to do that and what the success rate has been in terms of survival of the patient? Dr P.R. Vouhe: Only one patient, with an intramural LAD, had to undergo a mammary bypass. The infant did well postoperatively without evidence of myocardial damage. He underwent coronary angiography 2 months later and the anastomosis was nicely patent..