Complete Repair of Pulmonary Atresia with Nonconfluent Pulmonary Arteries

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1 Complete Repair of Pulmonary Atresia with Nonconfluent Pulmonary Arteries Francisco J. Puga, M.D., Dwight C. McGoon, M.D., Paul R. Julsrud, M.D., Gordon K. Danielson, M.D., and Douglas D. Mair, M.D. ABSTRACT From 1973 through 1979, 1 patients with pulmonary atresia, two normal-sized ventricles, and bilateral but nonconfluent pulmonary arteries underwent complete repair at the Mayo Clinic. Mean age at operation was 9.1 years (standard deviation [SD] 5.2 years). Sources of pulmonary flow were previous surgical shunts, patent ductus arteriosus, and discrete systemic-pulmonary arterial collaterals. The complete surgical repair included interruption of extracardiac shunts, closure of ventricular septal defect (15 patients), closure of atrial septal defect (3 patients), and establishment of right ventricular-pulmonary arterial continuity with a porcine-valved extracardiac conduit anastomosed to a transverse limb (T graft in 12 patients) or to a side-limb (Y graft in 4 patients). There were no operative deaths. Morbidity included reoperation for bleeding in 3 patients and compression of the prosthetic graft by the sternal closure in 1. The mean postrepair ratio of right ventricular peak systolic pressure to left ventricular peak systolic pressure (prvlplv) was 0.4 (SD, 0.23). Follow-up ranged from 12 to 72 months (mean, 34. months; SD, 20.7 months). One patient died 12 months after operation (postrepair prvlplv, 1.3). Conduit obstruction has been proved in 4 patients, of whom 3 underwent reoperation for extracardiac conduit obstruction at 4,47, and 48 months. The remaining 11 patients are alive and free of major symptoms. Nonconfluence of the main right and left pulmonary arteries constitutes a subset of an anomaly characterized by pulmonary arterial atresia. In nonconfluence, the atresia has ex- From the Division of Thoracic, Cardiovascular, Vascular, and General Surgery, the Department of Diagnostic Radiology, and the Division of Pediatric Cardiology, Mayo Clinic and Mayo Foundation, Rochester, MN. Presented at the Eighteenth Annual Meeting of The Society of Thoracic Surgeons, Jan 11-13, 1982, New Orleans, LA. Address reprint requests to Dr. Puga, Mayo Clinic, Rochester, MN tended beyond the bifurcation of the pulmonary artery trunk, so that the right and left pulmonary arteries originate separately and are not interconnected. In two large series of patients having pulmonary atresia associated with ventricular septal defect (VSD), the incidence of nonconfluence was 5% (3/2) [ll and 11% ( ) [2]. To date, these patients have not been reviewed specifically, although they present important surgical challenges. The present report includes all patients in whom this anomaly has been repaired at the Mayo Clinic. Material and Methods The records of all patients operated on at the Mayo Clinic for pulmonary atresia through October, 1981, were reviewed to identify cases of nonconfluence of the pulmonary arteries. Pulmonary atresia is defined as complete congenital obstruction of at least a segment of the blood-flow pathway from a ventricular chamber to one or both of the pulmonary arteries. Such a condition requires that the blood supply to the lungs beyond the segment of occlusion be derived from channels bypassing the obstruction; these are channels from the systemic circulation. Delineation of pulmonary arterial anatomy and the sources of pulmonary blood flow was accomplished by one or more of the following techniques: (1) aortography, (2) selective opacification of previously constructed surgical systemic-pulmonary arterial shunts, (3) selective opacification of systemic-pulmonary arterial collaterals, and (4) retrograde opacification of pulmonary arterial branches by pulmonary vein wedge injection. Pulmonary arterial diameter was assessed by direct measurement of the angiographic image of the pulmonary arteries, with correction for magnification by a factor derived from the measured image and known size of the angiographic catheter. The /83/ $01.50 Q 1982 by The Society of Thoracic Surgeons

2 37 Puga et al: Pulmonary Atresia with Nonconfluent Pulmonary Arteries size of the pulmonary arteries was then expressed as a percentage of the normal size for the patient s age and weight derived from published tables [31. The anomaly was repaired by interruption of systemic-pulmonary arterial shunts, closure of all intracardiac septal defects, and establishment of continuity between the right ventricle and both pulmonary arteries using a composite graft consisting of a valved extracardiac conduit connected to a side branch in a Y or T configuration. Data from patients records were analyzed. At follow-up, the status of each patient was determined by a direct examination or by a telephone inquiry to the patient, a parent, or the referring physician. Patient Data Sixteen patients with the defined anomaly have undergone complete surgical repair at the Mayo Clinic. The first procedure was performed in February, 1973, and the most recent, in October, During the same period, a total of 12 patients with pulmonary atresia were seen at the Mayo Clinic. Table 1 shows a classification of these patients according to the anatomy of their central pulmonary arteries. Nonconfluence was demonstrated in 19% of the total group (34/178). Ten of these patients had bilateral hypoplasia of the pulmonary arteries. Operative repair was contraindicated by elevated pulmonary arterial resistance in 3 patients and by arborization abnormalities in 5 others. The remaining 1 patients form the basis for this report. The ages of the patients at operation ranged from 4 to 24 years (mean age, 9.1 years; standard deviation [SDI, 5.2 years). There were 9 male and 7 female patients. Nine patients had undergone palliative procedures previously: Waterston shunts in patients, bilateral B1alock;Taussig shunt in 1, right Blalock- Taussig shunt in 1, and modified Potts shunt in 1. In the modified Potts shunt, the left pulmonary artery and the descending aorta had been joined by end-to-side anastomosis. All patients were cyanotic and exhibited marked intolerance to exercise, and all-in varying degree-had polycythemia and clubbing of dig- its. By definition, all patients had interruption of ventriculopulmonary arterial continuity (pulmonary atresia) and right and left main pulmonary arteries that were not confluent. Each had two normal-sized ventricles. Fifteen patients had a large VSD and 1 had an intact ventricular septum. Associated cardiovascular anomalies included transposition of the great vessels in 2 patients, juxtaposition of the atrial appendages in 1, atrial septal defect in 3, and anomalous origin of the left anterior descending coronary artery from the right coronary artery in 1. The sources of blood flow to each pulmonary artery in this series are summarized in Table 2. Figures 1, 2, and 3 are representative angiograms obtained by the radiological techniques mentioned previously. Hypoplasia of one of the two main branches of the pulmonary artery was noted in 7 patients; it involved the right pulmonary artery in 5 and the left pulmonary artery in 2. In each of these patients, however, the contralateral pulmonary artery was of normal size. In the remaining 9 patients, both pulmonary arteries were of normal size. The pulmonary arteries had full distribution throughout the lung fields in all patients. The position of the most proximal lumen of the pulmonary arteries was estimated from the anteroposterior angiogram and confirmed at operation; the relation to constant anatomical landmarks is summarized in Table 3. Surgical exposure of pulmonary arteries contained within the lateral limits of the pericardial cavity proved easier than exposure of those found lateral to the pericardium. Measurement of pulmonary artery pressure was possible in only 4 patients, in whom the exploring catheter was manipulated across a previous surgical shunt into one of the pulmonary arteries. In these 4, the mean pulmonary artery pressure was low (15, 12, 11, and 17 mm Hg). Surgical Technique A median sternotomy was the sole approach used in 15 patients. In 1 patient, a simultaneous left thoracotomy was also performed to gain control of an end-to-side Potts anastomosis. In this patient, a hypoplastic right pulmonary artery had been demonstrated only by pulmonary

3 38 The Annals of Thoracic Surgery Vol 35 No 1 January 1983 Table 1. Classification of 178 Patients with Pulmonary Atresia and Ventricular Septa1 Defect According to Central Pulmonary Arterial Anatomy Description of Anatomy Confluent large pulmonary arteries Confluent hypoplastic pulmonary arteries Nonconfluent large pulmonary arteries Nonconfluent hypoplastic pulmonary arteries Single large pulmonary artery Single hypoplastic pulmonary artery Absence of pulmonary arteries Total No. of Patients Percent of Total Table 2. Sources of Blood to Pulmonary Arteries in 1 Patients Having Pulmonary Atresia with Nonconfluent Pulmonary Arteries Pulmonary Arteries Source Ductus arteriosus Systemic collaterals Blalock-Taussig shunt Waterston shunt Modified Potts shunt (end-to-side) Total Left (No. of Patients) Right (No. of Patients) vein wedge injection. Before cardiopulmonary bypass (CPB) was begun, intrapericardial structures and functioning surgical shunts were thoroughly exposed; exposure of intrapericardial pulmonary arteries was also achieved at this time. Extrapericardial pulmonary arteries, present in the pulmonary hilus, were often more difficult to dissect because they were surrounded by multiple collateral vessels. Usually, they were best exposed with the patient on bypass and the lungs collapsed. The CPB apparatus included a bubble oxygenator. Core hypothermia from 22" to 24 C was induced in all patients, allowing pump flow to be kept as low as 1.0 Wmin/m* for brief periods during portions of the pulmonary artery reconstruction. The aorta was crossclamped intermittently for periods lasting up to 15 minutes in the first 14 patients; in the last 2, myocardial protection during a single period of aortic cross-clamping was achieved by cold cardioplegic and potassium cardioplegic arrest of the heart. Duration of extracorporeal circulation ranged from 115 to 243 minutes (mean, 13 minutes; SD, 22.1 minutes). The total duration of aortic cross-clamping ranged from 2 to 127 minutes (mean, 1 minutes; SD, 17.3 minutes). On institution of bypass, surgical shunts were interrupted and discrete systemic-pulmonary arterial collaterals were expased and ligated in continuity [4]. Closure of the VSD in 15 patients was achieved through a high incision in the outflow portion of the right ventricle. Intracardiac Teflon patches were used in all patients (Fig 4A). In 2 patients with transposition of the great arteries, a tunnel was created to connect the VSD with the subaortic outflow tract. Establishment of right ventricular-

4 39 Puga et al: Pulmonary Atresia with Nonconfluent Pulmonary Arteries Fig 1. Angiogram of the descending aorta. The left pulmonary artery is supplied by patent ductus arteriosus. Systemic collateral arteries are seen crossing the midline toward the right upper lobe. Fig 3. Angiogram of the descending aorta. The right pulmona y arte ry is supplied by a large systemic collateral arising from the innominate artery; the left pulmonary artery originates from patent ductus arteriosus. Table 3. Position of Most Proximal Lumen of Pulmonary Arteries in 1 Patients Having Pulmonary Atresia with Nonconfluent Pulmonary Arteries Position No. of Patients RIGHT PULMONARY ARTERY Medial to SVC Posterior to SVC Extrapericardial Total Fig 2. Angiogram of the patient in Fig I. A right pulmonary vein wedge injection is shown opacifying in retrograde fashion the right pulmonary artery. pulmonary arterial continuity required a composite graft in every patient (Table 4). In 12, a T reconstruction was accomplished by anastomosing a woven Dacron graft to both pulmonary arteries, thus creating a confluence. This graft was placed either anteriorly or posteriorly to the ascending aorta, and the right ventricle was then connected to the new pulmonary confluence with a Dacron conduit* containing a porcine heterograft valve (see Fig 4C). In the *Hancock Laboratories, Anaheim, CA. LEFT PULMONARY ARTERY Intrapericardial Ductal level Lateral to ductus Total SVC = superior vena cava. other 4 patients, a Y reconstruction was accomplished by connecting the right ventricle directly to one of the pulmonary arteries with a valved Dacron conduit and then anastomosing a side-arm graft of woven Dacron distally to the second pulmonary artery (see Fig 4B). In 15 patients, the diameter of the valved conduit ranged from 20 to 25 mm; the diameter of the 5 5 1

5 40 The Annals of Thoracic Surgery Vol 35 No 1 January 1983 Fig 4. Operative procedure for repair of pulmonary atresia with nonconfluent pulmonary arteries. (A) lnterruption of patent ductus arteriosus supplying left pulmonary artery and of systemic collateral supplying right pulmonary artery; patch closure of ventricular septa1 defect. (B) Reconstruction of pulmonary outflow with Y composite graft; side limb to right pulmonary artery placed behind aorta. (C) Reconstruction of pulmonary outflow with T composite graft. Table 4. Type of Extracardiac Reconstruction Reconstruction Position of Side-arm T Graft Y Graft Anterior to aorta 9 1 Retroaortic 3 3 Total 12 4 side-arm graft ranged from 12 to 1 mm, depending on the age and size of the patient. In one patient, aged 4 years, a 14 mm valved conduit and an 8 mm side branch were used. An atrial septa1 defect, present in 3 patients, was closed by direct suture. Hemostasis after discontinuation of bypass was often difficult, but use of fresh-frozen plasma and platelet concentrate proved helpful. Pressure measurements were recorded from all cardiac chambers and great vessels prior to wound closure. Results There were no operative or in-hospital deaths. mree patients required reoperation because of bleeding, but the remainder of their postoperative course was uneventful. Most patients required mechanical ventilation for at least 3 days, and six required inotropic support during the first 24 hours. One patient, aged years, in whom a T graft was placed with the transverse limb anterior to the ascending aorta, became severely hypotensive and bradycardiac when approximation of the sternal halves was attempted. The problem was solved by resecting subperiosteally a sternal fragment overlying the prosthesis; the anterior periosteum was then approximated over the graft, and the wound closure was accomplished uneventfully in the usual fashion. The average hospital stay for all patients was 13 days. The right ventricular peak systolic pressure divided by the left ventricular peak systolic pressure (prvlplv pressure ratio) recorded at the end of operation ranged from 0.27 to 1.3 (mean, 0.4). Among the 15 patients surviving to the present, 3 had a prvlplv less than 0.5; in 12 others, the ratio ranged from 0.5 to 1.0. One patient had a prvlplv of 1.3 recorded at the end of operation; this was a 4-year-old child in whom a T reconstruction had been made with a 14-mm valved conduit and an 8-mm woven

6 41 Puga et al: Pulmonary Atresia with Nonconfluent Pulmonary Arteries Table 5. Postoperative Cardiac Catheterization Data and Current Status in 7 Patients Undergoing Operation for Pulmonary Atresia with Nonconfluent Pulmonary Arteries Age at prvlplv Patient Operation Type of Months to No. (Yd Graft Catheterization Early Late Current Status 2 8 Y Y T T T T T 38 areoperation for conduit obstruction has been recommended to the patient NYHA Class IIa Reop.; alive and well Reop.; alive and well NYHA Class I Reop.; alive and well Residual VSD NYHA Class I prv/plv = ratio of right ventricular peak systolic pressure to left ventricular peak systolic pressure; NYHA = New York Heart Association; Reop. = underwent reoperation; VSD = ventricular septa1 defect. Dacron graft. Postoperative bleeding was controlled by early reoperation, but in the following year, the patient experienced progressive cyanosis, and he died 12 months after operation. Postmortem examination showed marked dilatation of the right ventricle, a small residual VSD, patency of the small extracardiac conduit and side branch, and thrombotic occlusion of numerous small pulmonary arterial branches. The length of follow-up has ranged from 12 to 72 months (mean, 34. months). Cardiac catheterization has been performed in 7 patients because of the appearance of symptoms, or auscultatory loss of pulmonary valve function, or both (Table 5). Three patients (3,4, and ) have undergone reoperation to replace obstructed conduits at 47, 48, and 4 months, respectively, after the original surgical procedure. Their ages at operation were 15,7, and 11 years. The reoperations were successful: 2 of the patients are now free of symptoms, and the other experiences dyspnea only on great exertion. In Patient 2, catheterization done 0 months after the initial surgical procedure has indicated conduit obstruction, with a prvlplv of 1.1. Reoperation has been recommended but not yet performed. At present, this patient- now 14 years of age-has dyspnea on strenuous exertion but leads an active life. The other 11 surviving patients are asymptomatic and also lead fully active lives. A postoperative angio- Fig 5. Postoperative pulmonary angiogram after T-graft reconstruction. gram for 1 of these patients is shown in Figure 5. The composite conduits removed from the 3 reoperated patients showed two kinds of intraluminal obstruction: a thick, fibrotic peel that partially obstructed the distal limb in all 3, and calcific stenosis that involved the porcine heterograft valve in 2. Comment In 195, Rastelli and colleagues [51 reported a repair of pulmonary atresia utilizing a conduit

7 42 The Annals of Thoracic Surgery Vol 35 No 1 January 1983 made of autologous pericardium for right ventricular outflow reconstruction. In 19, Ross and Somerville [1 reported the use of an aortic homograft conduit in repair of this anomaly. Proposing a classification of patients with pulmonary atresia in 1974, Berry and associates [7] noted that 3% of their patients had two nonconfluent pulmonary arteries. Kouchoukos and co-workers [8], reporting on a series of patients undergoing operation for pulmonary atresia and VSD, described 1 patient who had nonconfluence of the pulmonary arteries and survived repair with an aortic allograft valve and a Dacron bifurcating graft. Pacific0 and his group [9] discussed the use of bifurcated composite valved conduits in correcting severe hypoplasia of the pulmonary confluence. Alfieri and colleagues [l] reported Y or T reconstruction of pulmonary atresia in 3 patients, none of whom survived operation. In 197, an article from our institution [21 gave brief consideration to 10 instances of T or Y reconstruction of pulmonary atresia. One patient in the series died; however, one of the limbs of his graft was anastomosed on the left side to a systemic collateral because no pulmonary artery could be found in the left lung. This patient has been excluded from our present series. In our present report, attention has been focused on a particular subgroup of patients with pulmonary atresia, namely those in whom bilateral pulmonary arteries can be demonstrated angiographically but who lack anatomical confluence, so that each pulmonary artery derives its blood supply from anatomically independent sources. Evolving angiographic imaging techniques [lo, 111 have made it possible to visualize pulmonary arterial branches in situations where more conventional techniques had failed to do so. A striking feature of our series was the absence of surgical mortality and serious morbidity despite the obvious complexity of the corrective operation. This suggests that with careful selection of patients and meticulous surgical technique, the results experienced by these patients can be highly acceptable. The frequency of reoperation to control bleeding in the early postoperative period was high (3 of 1 patients), implying a need for further attempts to achieve hemostasis prior to wound closure. Meticulous construction of the distal graft-pulmonary artery anastomosis is especially important if the site of anastomosis is extrapericardial, because in that circumstance the exposure of bleeding points after the patient has been weaned from CPB may be fraught with difficulties. In the selection of patients for surgical treatment, demonstrated hypoplasia of the pulmonary arteries adds a complication of ongoing interest [l, 121. It is not discussed here because each patient in this series had at least one pulmonary artery of normal diameter. Nevertheless, it is possible to have two nonconfluent pulmonary arteries, both of which are hypoplastic. Patients with this variation have not been considered candidates for complete repair or for right ventricular outflow reconstruction. Our general requirement for corrective operation in pulmonary atresia has been the presence of at least one normal-sized pulmonary artery at the pulmonary hilus. Among the patients reported here, there were no notable abnormalities in the peripheral distribution of the pulmonary arteries, although in other patients with confluent pulmonary arteries, we have required that at least the equivalent of one lung be supplied by "true" pulmonary arteries. Alfieri and co-workers [l] proposed an equation to predict postrepair prvlplv from such variables as the diameters of the pulmonary arteries and descending aorta, the body surface area, and abnormalities in arterial arborization. The changes observed in extracardiac prosthetic conduits explanted after being used for pulmonary outflow reconstruction were recently reported by our institution [13]. The appearance of intraluminal obstruction, with consequent rise in right ventricular pressure, prompted recommendation for reoperation in 4 of our 1 patients, 4 to 5 years after the original surgical procedure. In addition, the need for selection of extracardiac conduits of adequate size (nonrestrictive) is emphasized by the observation that the 1 patient in our series who received a conduit of inadequate size-a 4- year-old child in whom a 14 mm valved conduit

8 43 Puga et al: Pulmonary Atresia with Nonconfluent Pulmonary Arteries and an 8 mm transverse limb were used-had the highest postrepair prvlplv (1.3) and was the only failure in our series (death occurred 12 months after operation). Although reoperation for replacement of obstructed extracardiac conduits can be accomplished safely, as evidenced by our 3 patients who underwent such reoperation, it is clear that a continuing search for better conduits is necessary if patients having this type of reconstruction or similar procedures are to consistently be spared the need for reoperation. The high incidence of conduit obstruction in this group of patients suggests that routine cardiac catheterization be carried out about 4 years postoperatively. References 1. Alfieri 0, Blackstone EH, Kirklin JW, et al: Surgical treatment of tetralogy of Fallot with pulmonary atresia. J Thorac Cardiovasc Surg 7:321, Olin CL, Ritter DG, McGoon DC, et al: Pulmonary atresia: surgical considerations and results in 103 patients undergoing definitive repair. Circulation 54:Suppl 3:35, Hurwitt E: The size of the pulmonary valve: a statistical analysis. Bull Int Assoc Med Museums 27:170, McGoon DC, Baird DK, Davis GD: Surgical management of large bronchial collateral arteries with pulmonary stenosis or atresia. Circulation 52:109, Rastelli GC, Ongley PA, Davis GD, et al: Surgical repair for pulmonary valve atresia with coronary-pulmonary artery fistula: report of case. Mayo Clin Proc 40:521, 195. Ross DN, Somerville J: Correction of pulmonary atresia with a homograft aortic valve. Lancet 2:144, Berry BE, McGoon DC, Ritter DG, et al: Absence of anatomic origin from heart of pulmonary arterial supply: clinical application of classification. J Thorac Cardiovasc Surg 8:119, Kouchoukos NT, Barcia A, Bargeron LM, et al: Surgical treatment of congenital pulmonary atresia with ventricular septal defect. J Thorac Cardiovasc Surg 1:70, Pacific0 AD, Kirklin JW, Bargeron LM Jr, et al: Surgical treatment of common arterial trunk with pseudohncus arteriosus. Circulation 5O:Suppl 2:20, Singh SP, Rigby ML, Astley R: Demonstration of pulmonary arteries by contrast injection into pulmonary vein. Br Heart J 40:55, Davis GD, Fulton RE, Ritter DG, et al: Congenital pulmonary atresia with ventricular septal defect: angiographic and surgical correlates. Radiology 128: 133, Piehler JM, Danielson GK, McGoon DC, et al: Management of pulmonary atresia with ventricular septal defect and hypoplastic pulmonary arteries by right ventricular outflow construction. J Thorac Cardiovasc Surg 80:552, Agarwal KC, Edwards WD, Feldt RH, et al: Clinicopathological correlates of obstructed right-sided porcine-valved extracardiac conduits. J Thorac Cardiovasc Surg 81:591, 1981 Discussion DR. ALDO R. CASTANEDA (Boston, MA): Dr. Francisco Puga and his colleagues from the Mayo Clinic deserve our admiration for the outstanding results achieved in managing such a technically challenging entity. This surgical tour de force was accomplished in an intelligently selected group of patients who, in addition to having pulmonary valve atresia, had at least one normal-sized central sixth aortic arch derived pulmonary artery proximal to the pulmonary hilum. It would be interesting to learn how many patients were deemed unsuitable candidates for repair during the same period because of either absence or hypoplasia of extraparenchymal pulmonary arteries, inadequate intraparenchymal distribution of pulmonary arteries, or unilateral or bilateral pulmonary artery hypertension secondary to previous shunt operations. In our experience, these complicating factors unfortunately coexist in a high proportion of patients. With regard to surgical technique, the critical issue of ligation of either direct or indirect aortopulmonary collaterals, or both, merits further discussion. Dr. Puga states, "On institution of bypass... discrete systemic-pulmonary arterial collaterals were exposed and ligated in continuity." How often was this necessary? According to Table 2, 15 systemic collaterals were identified preoperatively as important sources of blood to either the right or the left pulmonary arteries. What criteria were used to indicate intraoperative ligation of these branches? Including the patient who died 12 months after operation with a prvlplv of 1.3, of the 8 patients studied at varying intervals after operation had a ratio of greater than 0.8; in fact, in 5 patients the ratio was greater than 1.0. Since this incidence of intraluminal obstruction of valved conduits seems inordinately high, one must wonder whether an elevated distal resistance might play a role in the increased and accelerated form of conduit obstruction. Intraoperatively recorded prvlplv tends to vary enormously, making comparisons with late postoperative measurements unreliable. I agree with Dr. Puga that a continuing search for improved valved conduits is important, although I am not altogether certain that valved conduits are necessary for this kind of right ventricular-pulmonary artery reconstruction.

9 44 The Annals of Thoracic Surgery Vol 33 No 1 January 1983 In the not-too-distant future, newer cineangiographic techniques, better understanding of the anatomy and physiology of aortopulmonary collaterals, and perhaps the use of microsurgery will hopefully aid in extending the surgical indications to those patients who require reconstruction of the pulmonary arteries at the hilum and perhaps even intraparenchymally-at present a surgical no man s land. DR. PUGA: The questions posed by Dr. Castaneda are very valid and continue to worry us in many ways. 1 do not have figures available to establish the frequency of operability for patients who have pulmonary atresia with nonconfluent pulmonary arteries, but I totally agree with him that complicating features, such as pulmonary hypertension induced by previous shunting or distribution anomalies of the pulmonary arteries and hypoplasia of both pulmonary branches, preclude this type of repair. The management of this particular subgroup of patients differs from that of patients with pulmonary atresia and nonconfluent pulmonary arteries, and in our institution, we either use shunts for palliation or attempt outflow reconstruction in an effort to induce pulmonary arterial enlargement. The question of systemic arterial collateral ligation or interruption during operation is important. Although the physiology of systemic collaterals is not understood completely, it is clear that unless one controls systemic collaterals during operation, the surgical field will be flooded with blood returning from the pump. This poses severe problems in terms of rewarming the heart or the patient; therefore, we elect to ligate the collaterals. Furthermore, the leftto-right shunt imposed in these patients in the postoperative period may indeed be deleterious. In our experience, collaterals that should be ligated are truly discrete collaterals that are identifiable by aortography, especially in those patients who have generous-sized hearts that reflect a major left-to-right shunt. The question of conduit obstruction is important and especially worrisome in these patients; it seems to mar the postoperative course and the good functional results obtained by our efforts. While I agree with Dr. Castaneda that the pressures measured at operation do not necessarily reflect late pressures, it is clear that they do at least indicate the presence or absence of pulmonary hypertension at that particular moment. 1 do not know why the incidence of obstruction of the conduits is higher. It is true that they are complex conduits, and probably the turbulence caused by the connections in the T or Y reconstruction may further induce the formation of the peel. The question of having a valve in the conduits is also valid; indeed, in selected extracardiac pulmonary reconstructions, we attempt to place conduits without valves to avoid the problem of valve calcification. But I think it is unwise to leave patients who have pulmonary atresia without a valve as there is strong evidence that the immediate mortality and morbidity is higherespecially in patients who have some restriction in pulmonary runoff and for whom we can predict fairly high right ventricular pressures at the end of repair. Notice from the American Board of Thoracic Surgery The Part I (written) examination will be held at the Amfac Hotel, Dallas/Fort Worth Airport, Dallas, TX, in January, The closing date for registration is August 1, To be admissible for the Part I1 (oral) examination, a candidate must have successfully completed the Part I (written) examination. A candidate applying for admission to the certifying examination must fulfill all the requirements for the Board at the time the application is received. Please address all communications to the American Board of Thoracic Surgery, 1440 E Seven Mile Rd, Detroit, MI