Surgical correction of types II and III truncus arteriosus

Surgical correction of types II and III truncus arteriosus In truncus arteriosus types II and III, one or both pulmonary arteries arise independently from either side of the truncus. In the surgical correction of this anomaly, we have utilized an operative technique in which the essential features are as follows: ventricular septal defect (VSD) closure, which directs left ventricular outflow into the truncus; (2) anastomosis of a Dacron tube containing a glutaraldehyde-preserved porcine aortic heterograft to the right ventriculotomy; (3) removal of a circumferential band of the truncus containing both pulmonary artery orifices; (4) tailoring of the band of truncus tissue into a generous cuff which is anastomosed to the distal end of the valved Dacron conduit; and (5) restoration of aortic continuity with a tubular Dacron graft. Since 1971, 4 children ages 2 to 9 years have undergone successful correction of truncus arteriosus types II or III by this technique. In one patient with marked pulmonary hypertension and congestive heart failure preoperatively, the pulmonary vascular resistance had reverted to normal by 3 years after the operation. In one patient in whom bronchial collaterals to the right pulmonary artery were present, postoperative left ventricular failure required reoperation for ligation of the collaterals. All 4 patients are asymptomatic and fully active 5 to 60 months postoperatively. None has evidence of stenosis or insufficiency of the heterograft valve.

Randall B. Griepp, M.D., Edward B. Stinson, M.D., and Norman E. Shumway, M . D . , Stanford, Calif.

.L runcus arteriosus is a congenital malformation of the heart in which a single arterial trunk arises from the ventricles. A ventricular septal defect (VSD) is invariably present. The truncus receives blood from both ventricles and delivers it to the systemic, pulmonary, and coronary circulations. According to the widely accepted classification of Collett and Edwards, 1 truncus arteriosus can be divided into four major types. In type I, a main pulmonary artery arises from the truncus; in type II, both right and left pulmonary arteries arise from the posterior aspect of the truncus; in type III, both pulmonary arteries arise from the lateral aspects of the truncus; and in type IV, the pulmonary vessels arise from the descending thoracic aorta. In the series of 80 cases reviewed by Collett and Edwards 1 and the series of 180 cases reviewed by Bharati and associates, 2 types II and III comprise approximately 40 per cent of all cases of truncus arteriosus. From the Department of Cardiovascular Surgery, Stanford University Medical Center, Stanford, Calif. 94305. Read at the Second Annual Meeting of The Samson Thoracic Surgical Society, Banff, Alberta, Canada, June 1-4, 1976. Address for reprints: Randall B. Griepp, M.D., Department of Cardiovascular Surgery, Stanford University Medical Center, Stanford, Calif. 94305.

Placement of a conduit between a right ventriculotomy and a distal pulmonary artery which had been severed from the pulmonic valve was first reported by Donovan. 3 This concept was extended by Rastelli, 4 who, in a series of 18 dogs, interposed a homograft aorta containing the aortic valve between a right ventriculotomy and the distal main pulmonary artery as a conduit for right ventricular outflow. The clinical feasibility of total correction of truncus arteriosus with a conduit was reported by McGoon 5 in 1968. Since then, nearly 100 additional surgical procedures in which a conduit is used for repair of truncus arteriosus have been reported. 6 - 1 1 The over-all operative mortality rate has averaged 30 per cent. Owing to the particular technical considerations in connecting a conduit to the pulmonary artery orifices in types II and III truncus arteriosus, we believe that these patients constitute a distinct group from the surgical standpoint. In this communication, we discuss the use of a simple technique for establishing continuity between the conduit and the pulmonary arteries in types II and III truncus arteriosus and report the successful utilization of this technique in our first 4 patients. The essential features of surgical correction of types II and III truncus arteriosus are as follows: (1) closure 345

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Fig. 1. Operative techniques for correction of truncus arteriosus types II and III. a, Cannulation for cardiopulmonary bypass has been performed. A left atrial drainage catheter is in place. The site of the right ventriculotomy is indicated, b, The truncus is clamped above the pulmonary artery orifices. The band of truncal tissue containing the pulmonary artery orifices which is to be excised is indicated by dotted lines. Patch closure of the ventricular septal defect is begun. of the VSD, which directs left ventricular outflow into the truncus; (2) anastomosis of a valved conduit to the right ventriculotomy; (3) removal of a circumferential band of the truncus containing the two pulmonary artery orifices; (4) tailoring of the band of truncus tissue into a generous cuff, which is anastomosed to the distal end of the conduit; and (5) restoration of aortic continuity with a Dacron graft (Fig. 1). Operative technique After performance of a median sternotomy and creation of a pericardial well by suturing the cut edges of the pericardium to the wound drapes, the pulmonary arteries are identified at the point where they emerge from the truncus and are mobilized within the pericardium by sharp dissection. The patient is systemically heparinized, and cannulas are inserted for cardiopulmonary bypass. Both venae cavae are cannulated via the right atrium, and the proximal aortic arch is cannulated for arterial inflow. Cardiopulmonary bypass is

initiated with a bubble oxygenator* at a flow rate of 70 to 100 c.c. per kilogram per minute. The heat exchanger in the bypass circuit is not activated and, with the blood at room temperature, the patient's temperature gradually falls to 30 to 32° C. Adjustable tourniquets are tightened around the superior and inferior venae cavae, the heart is electrically fibrillated, and a small drainage tube is placed in the left atrium to allow cardiac decompression. The truncus is cross-clamped just below the origin of the innominate artery, and the myocardium is immediately cooled to approximately 15° C. by lavage of the pericardial cavity with several liters of saline at 4° C. Continuous infusion and aspiration of cold saline into the pericardial well is carried on during the remainder of the period of cross-clamping to maintain myocardial hypothermia. * Harvey oxygenator, Series H-200, William Harvey Research Corp., Santa Ana, Calif.

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2>A1

Fig. 1. Cont'd, c, Closure of the ventricular septal defect is complete. The cuff of truncal tissue including the pulmonary artery orifices has been excised and trimmed, d, A Dacron conduit containing a heterograft valve has been anastomosed to the right ventriculotomy. Continuity of the vessel, which is now the aorta, is being restored with a Dacron graft. A generous vertical ventriculotomy is made in the upper portion of the right ventricle, and the VSD is identified. The edges of the defect are rimmed with a series of interrupted horizontal mattress sutures which are then passed through a Teflon patch. In the superior portion of the VSD, the sutures are placed so that the truncal valve remains entirely on the left side of the patch, and thus the right ventricle is isolated from the systemic circulation. The right ventriculotomy is enlarged if necessary, and a suitably sized Dacron graft containing a glutaraldehyde-preserved porcine aortic heterograft is anastomosed to the right ventriculotomy.* The truncus is opened with an anterior incision and, after the orifices of both pulmonary arteries and those of the coronary arteries are visualized, a generous band of tissue containing the orifices of both pulmonary arteries is excised from the truncus. This band is then opened *Hancock Laboratories, Inc., Anaheim, Calif.

with an anterior vertical incision and trimmed to provide a generous cuff of tissue containing the two pulmonary artery apertures. A preclotted tubular Dacron graft is utilized to restore truncal or, more appropriately, aortic continuity. By interposition of a length of graft longer than the segment of truncus which was excised, the ascending aorta is displaced to the right. During placement of the graft, the heat exchanger in the cardiopulmonary bypass circuit is activated, and gradual warming of the patient is begun. The patient is placed in a reversed Trendelenburg position, the left ventricular apex and the ascending aorta are vented for air, and the cross-clamp is removed. The valved Dacron conduit is positioned in a gentle curve to the left of the aorta, trimmed to size, and then anastomosed to the truncal button containing the two pulmonary artery orifices. The left atrial cannula is removed, the left ventricular apex and ascending aorta are aspirated, and the heart is defibrillated.

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Fig. 1. Cont'd, e, The aortic cross-clamp has been removed. The conduit-pulmonary artery anastomosis is begun./, The completed operation. Following a short period of support, bypass is discontinued, the bypass moved, protamine is administered for and the chest is drained and closed in

cardiopulmonary cannulas are reheparin reversal, routine fashion.

Case reports Four patients have undergone surgical correction of types II or III truncus arteriosus. Pertinent preoperative, operative, and postoperative data are listed in Table I. Individual case reports are summarized below. CASE 1. The patient was a 9-year-old white boy weighing 27 kilograms. Mild cyanosis and a heart murmur were noted when he was 3 days of age, and cardiac catheterization and angiography carried out at 3 months of age demonstrated a truncus arteriosus type II. Between the ages of one and 8 years, he was noted to tire easily and become cyanotic with moderate exertion. One year prior to operation, severe biventricular failure appeared, resulting in orthopnea, marked dyspnea on exertion, peripheral edema, and ascites. Repeat cardiac catheterization 6 months prior to operation confirmed the diagnosis of truncus arteriosus type II and, in addition, demonstrated elevated end-diastolic pressures in both ventricles, moderately severe pulmonary hypertension with a pulmonary-to-systemic resistance ratio of 0.6, and an arterial oxygen saturation of 81 per cent. The possibility of operative intervention was dismissed because of the pulmonary hypertension. Over the next few months, increasingly severe congestive heart failure and cyanosis resulted in restriction to a bed-chair existence and, because of the dismal prognosis without operation, surgical correction was offered. Surgical correction by the technique just outlined was carried out on July 7, 1971. Postoperative complications consist-

ing of low output, respiratory insufficiency, and renal insufficiency gradually resolved, and the patient was discharged on the twenty-seventh postoperative day. Digitalis, diuretics, and salt restriction was required for one year postoperatively, but thereafter the patient became asymptomatic on full activity without cardiac medication. Cardiac catheterization 3 years postoperatively demonstrated small gradients at both proximal and distal anastomoses of the conduit. Evidence of ventricular failure and pulmonary hypertension had completely disappeared (Table II). Five years postoperatively, the patient remains asymptomatic and now weighs 75 kilograms. CASE 2. The patient was a 2-year-old girl weighing 10 kilograms. A murmur and mild cyanosis were noted shortly after birth. Cyanosis on exertion persisted, and dyspnea on exertion progressed to mild dyspnea at rest by the time of hospital admission. Cardiac catheterization at 21 months of age suggested the presence of truncus arteriosus of unknown type. Repeat catheterization just before the operation documented truncus arteriosus type II. Pulmonary artery pressures were equal to systemic, but pulmonary flow was markedly increased, so that there was a pulmonary-tosystemic resistance ratio of 0.09. The peripheral arterial oxygen saturation was 90 per cent. Left ventricular end-diastolic pressure was 19 torr. Operative correction as just outlined was performed on Nov. 19, 1974. A satisfactory postoperative course was marred only by drainage of lymph from the superior aspect of the sternotomy wound. This lymph fistula closed spontaneously, and the child was discharged from the hospital on postoperative Day 26. At present the child is asymptomatic, is normally active, and is growing normally. CASE 3. The patient was a 6-year-old white girl weighing 15 kilograms. A heart murmur was noted soon after birth, but she remained well until 6 months of age, when she required

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Table I. Summary of patient data Case No.

Preoperative data Sex, age (yr.) Truncus type Weight (Kg.) Symptoms Rp/Rs Intraoperative data RV-PA conduit size (mm.) Aortic interposition graft size (mm.) Perfusion time (min.) Aortic cross-clamp time (min.) Postoperative data Postoperative hospital stay (days) Complications Follow-up (mo.) Present status

1

2

3

4

M, 9

F, 2 II 10 Fatigue, decreased growth 0.09

F, 6 III 15 Fatigue, decreased growth 0.7

M, 3 II 13 Mild fatigue

n

27 Cyanosis, CHF 0.60 22 20 145 88

16 20 131 82

27 26 Low output, CHF, ventri- Mediastinal lymph cular irritability fistula 58 18 Asymptomatic, no Asymptomatic, no medication medication

20 + 8

91 46 19 Transient neurologic deficit, CHF, reoperation required 7 Asymptomatic, digoxin

0.26 20 22 137 95 17 None 6 Asymptomatic, no medication

Legend: Rp/Rs, Pulmonary-to-systemic resistance ratio. RV-PA, Right ventricle-pulmonary artery. CHF, Congestive heart failure.

hospitalization for an episode of congestive heart failure. At one year of age, cardiac catheterization revealed equal right and left ventricular pressures, a VSD, and possible origin of the pulmonary arteries from the ascending aorta. Following the catheterization, the child continued to develop normally and enjoy normal exercise tolerance. Repeated episodes of pneumonia required hospitalization once or twice yearly. Two months before admission, repeat catheterization confirmed the diagnosis of truncus arteriosus. The left pulmonary artery arose from the lateral aspect of the truncus; the right pulmonary artery filled somewhat later, and its exact origin from the aorta was not determined. Peripheral arterial oxygen saturation was 83 per cent, and the pulmonary-tosystemic resistance ratio was estimated to be 0.7. Of note on physical examination was a continuous murmur audible between the right scapula and the spine. The operation was performed on Nov. 11, 1975. The intracardiac anatomy was found to be that of truncus arteriosus with a large VSD. The left pulmonary artery arose from the side of the truncus. A small vessel thought to be a bronchial collateral connected the left pulmonary artery to the right pulmonary artery. Following fibrillation of the heart and clamping of the truncus, a large volume of blood was noted to be returning to the heart and exiting via the left atrial catheter. Left atrial drainage was measured and found to be two thirds of the total cardiopulmonary bypass flow. Local cooling of the heart and right lung, along with systemic cooling with the heat exchanger in the cardiopulmonary bypass circuit, gradually reduced this bronchial flow to a small fraction of total bypass flow, and the operation was continued. The left pulmonary artery was cut off of the lateral aspect of the truncus and anastomosed end to end to a 20 mm., valve-containing Dacron conduit. An 8 mm. graft was placed from the side of the conduit to the right pulmonary artery.

Postoperatively, it became evident that the patient had had some degree of cerebral hypoperfusion during bypass, probably secondary to shunting of blood via bronchial collaterals from the aorta into the left atrium. The moderate hemiplegia which ensued on the right side gradually cleared by the time of her discharge 19 days following the operation. During her hospital stay, however, she continued to have congestive heart failure requiring administration of digitalis and diuretics. One week following discharge she was readmitted with severe failure of the left side of the heart. The previously noted continuous murmur was still present. Repeat cardiac catheterization and angiograms confirmed the integrity of the repair but indicated a large left-to-right shunt through bronchial vessels into the right pulmonary artery. On Dec. 8, 1975, the patient was returned to the operating room. Through a right thoracotomy, three large bronchial vessels passing from the aorta to the right pulmonary artery were identified and ligated. The postoperative course was gratifyingly smooth, and the patient was discharged on the sixth postoperative day. She has continued to be well for the past 5 months. CASE 4. The patient was a 3'/2-year-old white boy weighing 13 kilograms. A heart murmur had been noted shortly after birth. The child tired easily and preferred playing quietly by himself rather than with other children. Cardiac catheterization and angiograms one month before the operation demonstrated type II truncus arteriosus. Left ventricular end-diastolic pressures were normal, the pulmonary artery pressures were the same as systemic pressures, but pulmonary flow was increased, so that the pulmonary-to-systemic resistance ratio was 0.26. Peripheral arterial oxygen saturation was 85 per cent. Surgical correction was carried out on Nov. 11, 1975. Excessive hemorrhage through the interstices of the aortic

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Table II. Catheterization data in Case 1 Six months preoperatively Right atrial pressure Right ventricular pressure Pulmonary artery pressure Left atrial pressure Left ventricular pressure Rp/Rs

-N20 110/15 110/80 -/-/15 110/15 0.60

Three years postoperatively 8/6/7 60/8 21/12/13 10/16/8 134/14 0.08

Legend: Rp/Rs, Pulmonary-to-systemic resistance ratio.

interposition graft was controlled by wrapping it with pericardium. The postoperative course was entirely uneventful, and the patient was discharged on the seventeenth postoperative day. Six months following the operation, he has become an aggressive and active child rather than a passive and withdrawn one. He requires no cardiac medication. Discussion Because of the successful outcome of these 4 cases, we believe that the operative technique outlined is a satisfactory one. Several technical considerations, however, merit additional emphasis. We believe that the Dacron tube containing a glutaraldehyde-preserved porcine aortic heterograft is the conduit of choice for restoration of right ventricular-pulmonary artery continuity in these patients.12 On the basis of experience with Dacron grafts elsewhere in the circulation, it is reasonable to assume that calcification and anastomotic stenosis should be rare, in contrast to the experience of others with conduits of homograft aorta.13 The Dacron tube is flexible and describes quite satisfactorily, without kinking, the complex curves required by this repair technique. The fabrication of the valve into the conduit wall provides a high ratio of valve orifice size to conduit size, so that a conduit of somewhat smaller diameter can be used than is possible with a homograft. The durability of the xenograft valve remains moot, but our experience with this valve in the mitral and aortic positions in adults suggests that a life-span of at least 5 to 6 years can be expected routinely.14 Should valvular integrity be lost, however, replacement of the valve by excising that portion of the conduit containing it and interposing a short graft containing a new valve should be a simple procedure. This is true, of course, only if the entire conduit does not require replacement. We believe that a 16 mm. conduit should be sufficiently large to provide adequate pulmonary circulation without marked right ventricular hypertension even after growth to adulthood. It is encouraging to note that a 16 mm. conduit can be satisfactorily placed in a child weighing only 10 kilograms (Case 2).

Removal of a circumferential portion of truncal wall containing the orifices of the two pulmonary arteries offers several advantages. Opening the anterior wall of the truncus first makes it possible, before incising the posterior wall, to identify the orifices of the pulmonary arteries as well as those of the coronary arteries; the latter are sometimes displaced superiorly in the truncus and invite inadvertent coronary artery injury.2 In addition, a generous cuff of tissue is provided which facilitates performance of the conduit-pulmonary artery anastomosis. Utilization of a Dacron graft to restore aortic continuity is technically advantageous, because a large button of the truncus can be removed to provide a satisfactory sewing cuff for the distal conduit anastomosis. Also, if the piece of graft material interposed in the aorta is slightly longer than the truncal tissue removed, the aorta will be elongated and can be displaced to the right. This prevents pressure on and kinking of the valved conduit by lateral pressure from the ascending aorta. It is necessary, however, to adequately preclot the segment of the aortic graft if bleeding through the graft interstices is to be avoided. Bleeding through the Dacron of the conduit on the right has not been a problem in our experience, probably because a protein coagulum forms in the Dacron material as a result of residual glutaraldehyde in the interstices of the Dacron cloth. Case 3 emphasizes the surgical importance of bronchial collaterals in patients in whom only one pulmonary artery arises from the truncus. It is extremely important to identify such collaterals and ligate them before the institution of cardiopulmonary bypass if massive shunting through the collaterals is to be avoided, with its attendant threat of hypoperfusion of other portions of the body. Moreover, the persistence of bronchial collaterals after correction of the truncus deformity will result in a substantial left-to-right shunt, occasionally resulting in left heart failure. The presence of a continuous murmur in a child with truncus arteriosus is indicative of bronchial collaterals, and a careful angiographic search for these vessels should be carried out as part of the preoperative work-up. The timing of operation in children with truncus arteriosus is problematic. It is inferred from the age at death in large autopsy series that approximately 80 per cent of patients with truncus types I, II, and III die prior to their first birthday.1' 2 Not only is the prospect of complete correction in children under one year of age uninviting from a technical standpoint, but also it is unlikely that one could place a conduit large enough to ensure that total revision with conduit replacement

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would not be necessary at a later date. The alternative of pulmonary artery banding, particularly in truncus types II and III, in which bilateral banding would be required, is a difficult procedure and, not surprisingly, is associated with a 50 per cent mortality rate. 8 Obviously, current surgical options regarding this entity are far from satisfactory, and additional approaches must be sought if the majority of patients with truncus arteriosus are to be saved. At present, the optimal strategy for management of the patient with truncus arteriosus type II or III is to observe him at relatively short intervals and check for increasing cyanosis by history, diminishing pulmonary blood flow on chest roentgenogram, and decreasing peripheral arterial oxygen saturation. When any of these parameters suggest increasing pulmonary vascular resistance, repeat cardiac catheterization is indicated. A pulmonary-to-systemic resistance ratio of 0.25 to 0.50 indicates the need for prompt surgical correction. It is hoped that, by so timing operative intervention, we can minimize the fraction of patients with truncus arteriosus who will require more than one operation. Finally, Case 1 in our series emphasizes the point that surgical treatment should not be withheld from children who have moderately severe pulmonary hypertension and congestive heart failure. The satisfactory long-term result in this patient and, in particular, the regression of pulmonary hypertension suggest that at least some of these children can be saved despite their desperate clinical status. Conclusion Four children have undergone successful operative correction of types II and III truncus arteriosus. Unique features of the operative approach utilized are related to construction of the conduit-pulmonary artery anastomosis. The technique involves the excision of a large band of truncal tissue containing the pulmonary artery orifices and tailoring of this vascular tissue to provide a generous cuff for suturing to the distal end of the conduit. The aorta is reconstructed by use of a tubular Dacron graft to elongate the aorta and displace it to the right in order to avoid pressure on and kinking of the right ventricular outflow conduit. REFERENCES 1 Collett, R. W., and Edwards, J. E.: Persistent Truncus Arteriosus: A Classification According to Anatomic Types, Surg. Clin. North Am. 29: 1245, 1949. 2 Bharati, S., McAllister, H. A., Rosenquist, G. C , Miller, R. A., Tatooles, C. J., and Lev, M.: The Surgical

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Anatomy of Truncus Arteriosus Communis, J. THORAC. CARDIOVASC. SURG. 67: 501,

1974.

3 Donovan, T. J., Hufnagel, C. A., and Eartcott, H. G.: Permanent Ligation of the Main Pulmonary Artery, Surg. Forum 2: 229, 1951. 4 Rastelli, G. C , Titus, J. L., and McGoon, D. C : Homograft of Ascending Aorta and Aortic Valve as a Right Ventricular Outflow, Arch. Surg. 95: 698, 1967. 5 McGoon, D. C , Rastelli, G. C , and Ongley, P. A.: An Operation for the Correction of Truncus Arteriosus, J. A. M. A. 205: 69, 1968. 6 McGoon, D. C , Wallace, R. B., and Danielson, G. D.: The Rastelli Operation, J. THORAC. CARDIOVASC. SURG.

65: 65, 1973. 7 Behrendt, D. M., Kirsh, M. M., Stern, A., Sigmann, J., Perry, B., and Sloan, H.: The Surgical Therapy for Pulmonary Artery-Right Ventricular Discontinuity, Ann. Thorac. Surg. 18: 122, 1974. 8 Poirier, R. A., Berman, M. A., and Stansel, H. C , Jr.: Current Status of the Surgical Treatment of Truncus Arteriosus, J. THORAC. CARDIOVASC. SURG. 69: 169, 1975.

9 Moore, C. H., Martelli, V., and Ross, D. N.: Reconstruction of Right Ventricular Outflow Tract With a Valved Conduit in 75 Cases of Congenital Heart Disease, J. THORAC CARDIOVASC. SURG. 71: 11, 1976.

10 Appelbaum, A., Bargeron, L. M., Pacifico, A. D., and Kirklin, J. W.: Surgical Treatment of Truncus Arteriosus With Emphasis on Infants and Small Children, J. THORAC. CARDIOVASC. SURG. 71: 436,

1976.

11 Bailey, L. L., Takeuchi, Y., Williams, W. G., Trusler, G. A., and Mustard, W. T.: Surgical Management of Congenital Cardiovascular Anomalies With the Use of Profound Hypothermia and Circulatory Arrest, J. THORAC CARDIOVASC SURG. 71: 485,

1976.

12 Bowman, F. O., Jr., Hancock, W. D., and Malm, J. R.: A Valve-Containing Dacron Prosthesis, Arch. Surg. 107: 724, 1973. 13 Park, S. C , Neches, W. H., Lenox, C. C , Zuberbuhler, J. R., and Bahnson, H. T.: Massive Calcification and Obstruction in a Homograft After the Rastelli Procedure for Transposition of Great Arteries, Am. J. Cardiol. 32: 860, 1973. 14 Stinson, E. B., Griepp, R. B., Oyer, P. E., and Shumway, N. E.: Long-Term Experience With Porcine Aortic Valve Xenografts, J. THORAC CARDIOVASC SURG. 73:

54, 1977. Discussion DR. G E O R G E G. L I N D E S M I T H Los Angeles, Calif.

I would like to congratulate Dr. Griepp and his associates on this fine piece of work. Since the use of valve conduits in reconstructing the right ventricular outflow tract and in repairing truncus is a relatively new procedure, it might be of value to reiterate some of the things Dr. Griepp has already said.

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[Slide] This is a classic drawing of types II and III truncus. It is stylized and is accepted as such. However, one must realize that these are really part of a continuum and that the pulmonary arteries can either be directly opposite each other on the truncal takeoff or can airse near each other from the posterior left lateral side of the truncus. [Slide] Actually, at operation, the immediate anatomic appearance of these vessels is not particularly clear and distinct. Often, one cannot tell at surgery exactly where these vessels are going to take off. This point strongly favors Dr. Griepp's procedure, since an anterior truncal incision immediately identifies the exact location of the pulmonary arterial orifices and facilitates the further repair. The standard repair of type II truncus has involved suturing a common orifice in the pulmonary artery to the cephalad end of the valve conduit. Of course, that incision can be tailored to allow a large anastomosis between the conduit and the pulmonary artery. In type III truncus, a button of the truncal tissue can be excised, in many instances, with the pulmonary arterial takeoff; thus there is an adequate cuff to suture to the valve conduit. One will note, however, that in both of these procedures

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truncal tissue is excised, the resulting aorta is shortened, and the arch lessened in its sweep. As a consequence, the arch is moved more to the left, positioning of the valve conduit is somewhat more difficult, and kinking is more likely. [Slide] This picture delineates the proximal end of the valve conduit. The incision in the ventricle must cross the fibers of the ventricular outflow tract at right angles. The resulting direction of the valve conduit can be aimed, so to speak, by orienting this incision. It should be slanted to the left so that the conduit will lie to the left side of the chest. Incising across these muscle fibers ensures that, during systole, this end of the anastomosis will pout open and not be obstructive. One other point: It is highly important that the valve in the valve conduit be placed as high as possible toward the pulmonary artery anastomosis. This allows for sternal closure without kinking or compromising the graft by having the heterograft valve directly anterior. D R . G R I E P P (Closing) I would like to thank Dr. Lindesmith for discussing the paper and for sharing with us his experience with this entity.