Conduit Reconstruction of Right Ventricular Outflow Tract

Transcription

1 Conduit Reconstruction of Right Ventricular Outflow Tract Experience with 17 Patients E. Ross Kyger, 111, M.D., Luigi Chiariello, M.D., Grady L. Hallman, M.D., and Denton A. Cooley, M.D. ABSTRACT Evaluation was made of 17 patients who underwent conduit reconstruction of the right ventricular outflow tract (for anomalies other than truncus arteriosus) at the Texas Heart Institute between December, 1965, and June, Fifteen patients survived the operation and have shown substantial clinical improvement. Several different conduits were used, principally an allograft aorta with the aortic valve and mitral leaflet attached, a woven Dacron prosthesis containing a xenograft (porcine) valve, and a valveless Dacron tube graft. Allograft conduits are sometimes difficult to procure and keep and tend to calcify with passage of time. Woven Dacron prostheses are favored because they are readily available in a wide range of sizes. We believe it is not necessary for the conduit to contain a valve unless the patient has pulmonary hypertension, in which case we use a xenograft (porcine) valve because this valve does not require the long-term use of anticoagulants, a difficult regimen to manage in children. The largest possible prosthesis must be used; otherwise right ventricular hypertension will persist. Indications for conduit reconstruction include anomalous coronary arteries crossing the right ventricular outflow tract, discontinuity of the pulmonary arteries, and pulmonary atresia with a ventricular septal defect. Our current method of managing pulmonary atresia with ventricular septal defect (pseudotruncus arteriosus) includes palliative shunting to relieve hypoxemia during infancy and to permit full development of the pulmonary arteries for eventual total correction at a more optimal age when a larger conduit may be used. A variety of congenital cardiac malformations may require conduit reconstruction of the right ventricular outflow tract. In 1955 Lillehei and his associates [5] reported a patient with pulmonary atresia and ventricular septal defect in whom total correction was performed by anastomosing the main pulmonary artery to the reconstructed right ventricular outflow tract. Ten years later Rastelli and colleagues [71 reported the first conduit reconstruction of this defect, using a tube of pericardium from the right ventricle to the main pulmonary artery. This was followed by a report from Ross and Somerville [8] of correction of pulmonary atresia with an improved conduit in the form of an aortic allograft with the aortic valve and its attached anterior mitral From the Division of Surgery of the Texas Heart Institute, St. Luke s Episcopal and Texas Children s Hospitals, Houston, Tex. Accepted for publication Oct. 29, Address reprint requests to Dr. Kyger, Texas Heart Institute, P.O. Box 20345, Houston, Tex VOL. 19, NO. 3, MARCH,

2 CLlNlCAL MATERlAL IN 17 PATIENTS WITH.TETRALOGY OF FALLOT WHO UNDERWENT CONDUIT RECONSTRUCTION OF THE RIGHT VENTRICULAR OUTFLOW TRACT Pressure after Repair Patient Hg) Age (yr) Date of Indication Peak Systolic & Sex Operation for Conduit Type of Conduit Reconstruction (RVILV) PA Results 1. 6, M 2. 13, F 3. 17, F 4. 21, M 5. 13, M (1st op.) 14, M (2nd op.) 6. 19, M 7. 10, M 8. 21, M 9. 10, F (1st op.) 12, F (2nd op.) , M 12/20/65 7/7/69 6/30/ /71 5/17/71 6/29/72 9/7/71 12/15/71 2/9/ /9/74 10/29/73, small RPA, no LPA in pericardium Atretic PV & proximal MPA Hypoplastic pulmonary annulus, anomalous LAD arising from RCA & crossing RV outflow tract Corrected transposition with severe pulmonary stenosis, hypoplastic pulmonary annulus; circumflex coronary artery crossed RV outflew tract Resected persistent LSVC used as conduit from RV to junction RPA & LPA Aortic allograft, RV to junction RPA & LPA Aortic allograft, RV to junction RPA & LPA Composite graft; proximal portion woven Dacron containing No. 21 Bjork valve, distal portion aortic allograft; RV to junction RPA & LPA Aortic allograft, RV to RPA; large collateral vessel to left lung preserved Irft pleural space explored; 8-mm woven Dacron graft from side of aortic allograft to end of LPA; enlarged proximal RPA with pericardial patch Aortic allograft, RV to junction RPA & LPA; pericardial patch to infundibulum l8-min woven Dacron graft containing No. 17 Bjork valve No. 19 Bjork valve contained between two 22-mm woven Dacron grafts anastomosed at an angle; conduit goes to RPA only; LPA end-to-end left subclavian artery at previous operation elsewhere 18-mm Dacron graft containing No. 17 Bjork valve Prosthetic valve removed Pulmonary valve excised; double-outlet venous ventricle created by using 12-mm woven Dacron graft from ventriculotomy to MPA Died, low cardiac - output 95/95 75' Died 18 hr postop.. sud Good result, allograft Good clinical result calcified den cardiac arrest 30/ '... loo/loo 30/ /10' ' 120l120 25/10' Improved, stenosis developed at distal anastomosis Good result Excellent long-term result Good clinical result Excellent result Excellent clinical im proverne n t Good clinical result

3 11. 27, F , M , M 14. 4, M , F F 11/21/73 1/16/74 4/12/74 5/1/74 5/23/74 6/26/74 Pulmonary hypertension; unable to wean from cardiopulmonary bypass after outflow patch reconstruction Atretic PV & proximal MPA Pulmonary valve stenosis, small annulus & MPA, anomalous LAD crossing RV outflow tract Very atretic PV Stenotic PV, hypoplastic annulus, MPA very small, LPA arising from stenotic ductus arteriosus Outflow patch removed; No. 18 Hancock prosthesis, RV to distal MPA 14-mm Hancock prosthesis; RV to junction RPA & LPA; thrombectomy LPA 18-mm Hancock prosthesis; RV to junction RPA & LPA Excised pulmonary valve; 12-mm woven Dacron graft, RV to MPA 16-mm Hancock prosthesis, RV to distal-mpa 16 X 8 mm woven Dacron bifurcation graft; one limb end-to-side LPA, doubly ligated ductus; other limb end-to-side MPA... 75/40 110/ /455 1 loll00 65/ / Much impmved, Functional Class 11; working part-time Much improved Much improved Excellent clinical result Excellent clinical result Excellent result , M 6/27/74 Stenotic PV, hypoplastic annulus, anomalous LAD arising from RCA & crossing RV outflow tract 12-mm woven Dacron graft, RV to side MPA Excellent result Pressure measured in operating room. +Cardiac cathererimtion three years postoperatively. 36atheterization after first operation on December 21, Catheterization six months after operation. 5Cardiac catheterization before discharge after operation. PA = pulmonary artery; RV = right ventricle; LV = left ventricle; PV = pulmonary valve; MPA = main pulmonary artery; RPA = right pulmonary artery; LSVC = left superior vena cava; LPA = left pulmonary artery; RCA = right coronary artery; LAD = left anterior descending coronary artery.

4 KYGER ET AL. FIG. 1. During reconstruction of the right ventricular outflow tract in Patient 1, a segment of persistent left superior uew cava (LSVC) was used for the conduit. leaflet. An earlier description of this type of prosthetic repair appeared in a textbook publication from this institution, where the technique had been utilized for truncus arteriosus [2]. McGoon, Rastelli, and Ongley [6] reported a successful repair of truncus arteriosus using a homograft valve and conduit. In 1971 Kouchoukos and co-workers [4] reported employing several different types of conduits for reconstruction of the right ventricular outflow tract in 10 patients with pulmonary atresia and ventricular septal defect. This report concerns conduit reconstruction of the right ventricular outflow tract in 17 patients. Materials and Methods The series included 11 male and 6 female patients ranging from 4 to 27 years of age who were operated upon at the Texas Heart Institute between December, 1965, and June, 1974 (Table). Of the group, 11 patients had pulmonary atresia with ventricular septal defect (pseudotruncus arteriosus), an extreme form of tetralogy of Fallot. Nine of the 11 patients had undergone previous palliative operations to increase pulmonary blood flow, and 1 had severe pulmonary hypertension associated with a functioning Potts anastomosis. Four patients had severe forms of pulmonary stenosis usually treated with a patch graft to the outflow tract, but a large anomalous coronary artery crossing the right ventricular outflow tract prevented application of that technique. One patient had a hypoplastic pulmonary annulus, a tiny main pulmonary artery, a small right pulmonary artery, and an anomalous left pulmonary artery arising from a stenotic patent ductus arteriosus. Another patient had tetralogy of Fallot and severe pulmonary hypertension associated with a functioning Potts anastomosis of long duration. Patch graft 280 THE ANNALS OF THORACIC SURGERY

5 Reconstruction of RV Outflow Tract repair of the right ventricular outflow tract resulted in pulmonary valvular insufficiency, and the patient could not be taken off the pump oxygenator. It was necessary then to remove the patch and interpose a valve-containing conduit between the right ventricle and pulmonary artery. Adequate cardiac function dramatically returned. All patients underwent cardiac catheterization before operation. Eleven patients had pressures measured after conduit reconstruction, either in the operating room or at subsequent cardiac catheterization. Operative Techniques Operation was performed through a median sternotomy using cardiopulmonary bypass with hemodilution. Functioning shunts were closed immediately after cardiopulmonary bypass was instituted. The decision to use a transverse or longitudinal right ventriculotomy was made to conform with the coronary anatomy of the particular patient. The ventricular septal defect was closed with a knitted Dacron patch, using double-ended running 4-0 polyester sutures. In Patient 1 (see the Table) a large persistent left superior vena cava was resected and used as a conduit from the right ventriculotomy to the junction of the right and left pulmonary arteries (Fig. 1). Four patients received aortic allografts containing the aortic valve with an attached mitral leaflet (Fig. 2). The allografts were harvested under semisterile VSD patch?epair FIG. 2. Technique of reconstruction using an allograft of aortic valve, ascending aorta, and attached anterior mitral valve leajlet. (VSD = ventricular septal defect.) VOL. 19, NO. 3, MARCH,

6 KYGER ET AL. /J(/ G kricardial patch FIG. 3. Technigue used in Patient 5. In thefirst operation, allograft reconstruction was made on4 to the right pulmonary artery, which was enlarged by a pericardial patch. In the second operation an 8-mm woven Dacron graj was used to restore continuity to a left pulmonary artery. conditions prior to the planned operative procedure and refrigerated in antibiotic solution until implantation. The proximal anastomosis was performed first, using the attached mitral leaflet to enlarge the proximal anastomosis to the ventriculotomy. The distal portion of the allograft was then trimmed and an anastomosis performed near the junction of the right and left pulmonary arteries. In 1 patient (No. 5) the anastomosis was made only to a small proximal right pulmonary artery, which was enlarged with a pericardial patch. A small left pulmonary FIG. 4. In Patient 7 a woven Dacron conduit containing a Bjork prosthetic valve was used in order not to injure an anomalous left anterior descending coronary artery arising from the right coronary artery. 282 THE ANNALS OF THORACIC SURGERY

7 Reconstruction of RV Outflow Tract FIG. 5. The heart of Patient 10, who had corrected transposition of the great arteries and severe pulmonary stenosis. The left coronary artery arose anteriorly from the aorta and the circumflex branch crossed the right ventricular outflow tract, thus preventing use of a patch to enlarge the hypoplastic pulmonary annulus. A woven Dacron bypass graft was used for the reconstruction. (VV = venous ventricle; AV = arterial ventricle; PT = pulmonary trunk; Ao = aorta.) artery was located in the pleural space at a second operation and connected to the allograft conduit with an 8-mm Dacron tube graft (Fig. 3). One patient received a composite graft as a conduit. A Dacron tube containing a No. 2 1 Bjork-Shiley valve was used as the proximal portion, and an allograft aorta formed the distal portion. Dacron tube conduits containing Bjork prosthetic valves were used in 3 patients (Fig. 4). Of these, 2 had No. 17 Bjork valves sewn into an 18-mm Dacron tube. In the third a No. 19 Bjork valve sewn into the slightly angledjunction of two Dacron tubes of 22 mm each was utilized. Three patients had valveless conduits placed in order not to injure a major coronary vessel; in another patient a conduit containing a prosthetic valve was used for the same purpose (see Fig. 4). One patient (No. 10) had corrected transposition of the great arteries and severe pulmonary stenosis. In this anomaly the left coronary artery arose anteriorly from the aorta and the circumflex branch crossed the right ventricular outflow tract, thus preventing the usual technique of outflow patch reconstruction (Fig. 5). The pulmonary valve was excised and a 12-mm woven Dacron tube was sewn to the ventriculotomy and to the main pulmonary artery, bypassing the obstruction. Other patients (Nos. 7, 14, and 17) had tetralogy of Fallot with a hypoplastic pulmonary annulus. A major coronary vessel crossed the pulmonary outflow tract to supply the septum and the apex of the heart. A woven Dacron tube was sewn to the ventriculotomy and then end-to-side to the main pulmonary VOL. 19, NO. 3, MARCH,

8 KYGER ET AL. FIG. 6. Egress from the right ventricle W obtained by two routes. Pulmonary valvotomy allows some improvement inflow by the normal anatomical route, and the conduit relieves what obstruction the hypoplastic annulus would cause. artery, sparing the coronary artery and creating a double-outlet right ventricle (Fig. 6). Commercially available Dacron tube grafts* containing xenograft (porcine) valves were used in 4 patients. As discussed earlier, one of the tube grafts was used in the patient with pulmonary hypertension because this patient could not be weaned from cardiopulmonary bypass after outflow patch repair. Three patients in the series received Hancock prostheses as conduits for repair of uncomplicated pulmonary atresia with ventricular septa1 defect. One patient (No. 16) required a bifurcation graft for reconstruction of the right ventricular outflow tract (Fig. 7). The left pulmonary artery arose from a stenotic ductus arteriosus. Poststenotic dilatation occurred, and the vessel wall was very thin and friable. The ductus was doubly ligated, and one limb of the graft was anastomosed end-to-side to the left pulmonary artery. A longitudinal arteriotomy was made on the main pulmonary artery proximal to the point where it curved beneath the aorta to become the right pulmonary artery. The second limb of the graft was anastomosed end-to-side to this arteriotomy, and the proximal portion was trimmed and sewn to the right ventriculotomy. Results Two hospital deaths (13%) and no late deaths occurred in the series (see the Table). Patient 1, a 6-year-old boy, never attained a satisfactory cardiac output after repair - a problem that was compounded by profuse postoperative hemor- *Hancock Laboratories, Inc., Orange, Calif. 284 THE ANNALS OF THORACIC SURGERY

9 Reconstruction of RV OutJlow Truct FIG. 7. Woven Dacron bijiwcation conduit in an unusual case of tetralogy of Fallot in which the l$t pulmonary arte? arose from a stenotic patent ductus arteriosus (PDA). rhage in this severely cyanotic and polycythemic child. In retrospect, the conduit may have been unsatisfactory because of its small size. Since the conduit in this patient did not contain a valve, the possibility exists that right ventricular failure may have resulted from pulmonary valve regurgitation due to possible elevation of pulmonary vascular resistance. The second death (Patient 2) was due to arrhythmia. This patient had been in stable condition for 18 hours after operation when ventricular fibrillation suddenly occurred and the patient could not be resuscitated. Elevated pulmonary vascular resistance was noted in this patient before operation, and equal right and left ventricular pressures were present after repair. Patients with this degree of right ventricular hypertension are susceptible to sudden death. The last 15 patients in the series are alive and well one month to four years after operation. Although all surviving patients have experienced remarkable symptomatic improvement, follow-up data have revealed some disconcerting facts. Three years after operation Patient 3 has a calcified allograft and a gradient of 60 mm Hg between the right ventricle and pulmonary artery. The pressure gradient is due partly to residual infundibular stenosis and partly to stenosis in the distal anastomosis. Patient 5 had a complicated postoperative course with profuse bleeding and acute tubular necrosis. He recovered full renal function, however, and has subsequently returned to full-time employment. All patients who received a conduit containing a prosthetic valve and for whom measurements are available have gradients across the valve. Patient 8 had a gradient of 37 mm Hg across a No. 19 Bjork valve. The clinical response of this VOL. 19, NO. 3, MARCH,

10 KYGER ET AL. patient, however, is excellent, and he is working full-time as an x-ray technician with no limitations. Patient 9, 10 years of age, underwent a second cardiac catheterization one year postoperatively and was found to have equal right and left ventricular pressures, a small persistent ventricular septa1 defect, and an 85 mm Hg gradient across a No. 17 Bjork valve. The pulmonary artery pressure distal to the valve was normal. Although her clinical result was excellent, reoperation was advised because of the very high right ventricular pressures. The prosthetic valve was removed at reoperation two years after the original correction. Two of 3 patients who underwent recatheterization after receiving a prosthesis containing a porcine valve have significant gradients across the valve. Patient 12, a 13-year-old boy, received a 14-mm Hancock prosthesis. He had a gradient of 45 mm Hg across the valve as well as increased pulmonary branch stenosis and required thrombectomy of the left pulmonary artery proximal to a functioning Blalock shunt at the time of correction. His early clinical course was satisfactory, although the right ventricular pressure exceeded the left ventricular pressure. His prognosis must therefore remain guarded. Patient 13, a 14-year-old boy, received an 18-mm Hancock prosthesis and at postoperative cardiac catheterization had a 70 mm Hg gradient across the porcine valve. Cineangiography revealed excellent inflow into the prosthesis, but only approximately 50% of the external diameter of the prosthesis appears to be available for flow through the valve. Patient 11, a 27-year-old woman, was much larger than Patient 13. She had received an 18-mm Hancock prosthesis, but only a 10 mm Hg gradient was demonstrated at postoperative cardiac catheterization. This patient had severe pulmonary hypertension, and cardiac output may have been so limited by the pulmonary vascular resistance that no significant gradient appeared. In this patient mechanical ventilatory assistance was necessary for several days; however, she was discharged from the hospital in satisfactory condition. Her long-term prognosis remains guarded because of the high pulmonary pressures. All 4 patients (Nos. 10,14,16, and 17) who received valveless Dacron conduits have experienced good clinical results and have had no difficulty from pulmonary insufficiency. Comment Results of this series and those from other authors [4, 10, 111 demonstrate that conduit reconstruction of the right ventricular outflow tract may be performed with reasonable risk in a variety of conditions. Still unclear, however, is which of the various types of conduits reported is best for clinical use. Most surgeons would agree that the use of a conduit containing a valve is desirable in the patient with pulmonary hypertension. An allograft ascending aorta with the aortic valve has an advantage over prosthetic valves in that anticoagulants, which might be difficult to manage in a child, are unnecessary. Allograft aortas, however, are difficult to procure and store for ready availability. The allograft aorta is known to calcify after a period of time, and whether this process will extend to 286 THE ANNALS OF THORACIC SURGERY

11 Reconstruction of RV Outflow Tract involve the valve leaflets is not yet known. Eguchi and Asano [3] and Seki and co-workers [9], in experiments with dogs, reported that pulmonary arterial allografts did not calcify when used as replacements for the outflow tract. To date, no clinical confirmation of this finding is available. The use of Dacron tube grafts as conduits offers several advantages to the surgeon. The easy availability of a variety of sizes and lengths is the most apparent. The ability to tailor the graft to fit the anatomical situation is another distinct advantage. Dacron tube grafts can be easily handled, and long-term clinical use confirms their acceptance by human tissue. Little is known about the long-term results with various types of valves in the lesser circulation. One might surmise that the lower pressures involved would extend the life of the valve no matter which type was chosen, but this assumption has not been proved. Flow at the pulmonary valve is equal to flow at the aortic valve, and since the lungs are less sensitive to small emboli than the systemic circulation, embolization may be less of a problem with prosthetic valves. Anticoagulation might be avoided altogether with some prostheses, such as the recently introduced Cooley-Cutter aortic valve which has a self-washing feature [I]. The most common anomaly requiring an outflow tract prosthesis is pulmonary atresia with ventricular septal defect, an extreme form of the same faulty embryological development of the conus-truncus that results in tetralogy of Fallot. This anomaly is frequently called pseudotruncus arteriosus. Our current method of managing these patients includes obtaining high-grade biplane angiography to confirm the presence, location, and size of the pulmonary arteries. In children weighing less than 60 pounds, a palliative shunt to increase pulmonary blood flow is performed. This serves two purposes: it allows the child to grow so that the largest possible conduit may be used later, and it encourages development of larger pulmonary arteries. Either a subclavian-to-pulmonary anastomosis or an intrapericardial ascending aorta-to-right pulmonary artery shunt is performed. After the child is larger, conduit reconstruction may be carried out, with closure of the ventricular septal defect. Other situations in which conduit reconstruction is helpful include tetralogy of Fallot with an anomalous coronary artery crossing the right ventricular outflow tract and corrected transposition with associated tetralogy of Fallot. In the latter anomaly a major coronary artery frequently loops around the pulmonary artery, preventing application of a patch across the annulus. We currently prefer a valveless woven Dacron tube conduit unless elevated pulmonary vascular resistance is present. In those situations we use the Hancock prosthesis containing a porcine valve. Because of the larger gradients we have encountered with the smaller-sized valves, we recommend using one no smaller than 20 mm. In larger patients this size still may be inadequate, and a composite graft of Dacron containing an aortic allograft, as recommended by Kouchoukos [4], may be preferable. Although more time is required for obtaining and constructing this conduit, it could easily be made in sizes to 25 mm, which should accommodate a normal cardiac output without significant gradients in almost all patients. VOL. 19, NO. 3, MARCH,

12 KYGER ET AL. References 1. Cooley, D. A. New mitral and aortic valve prostheses: Design and clinical results. Cardiovmc Dis (Bull Tex Heart Inst) 1:46, Cooley, D. A., and Hallman, G. L. Surgical Treatment of Congenital Heart Disease. Philadelphia: Lea & Febiger, Pp Eguchi, S., and Asano, K. Homograft of pulmonary artery or ascending aorta with valve as a right ventricular outflow.] Thorac Cardiovusc Surg 56:413, Kouchoukos, N. T., Barcia, A., Bargerone, L. M., and Kirklin, J. W. Surgical treatment of congenital pulmonary atresia with ventricular septal defect. ] Thorac Cardiouusc Surg 6 l : 70, 197 l. 5. Lillehei, C. W., Cohen, M., Warden, H. E., Read, R. C., Aust, J. B., DeWald, R. A., and Varco, R. L. Direct vision intracardiac surgical correction of the tetralogy of Fallot, pentology of Fallot, and pulmonary atresia defects: Report of the first ten cases. Ann Surg 142:418, McGoon, D. C., Rastelli, G. C., and Ongley, P. A. An operation for the correction of truncus arteriosus. JAMA 205:69, Rastelli, G. C., Ongley, P. A., Davis, G. D., and Kirklin, J. W. Surgical repair for pulmonary valve atresia with coronary artery fistula: Report of a case. Mayo Clin Proc 40:521, Ross, D. N., and Somerville, J. Correction of pulmonary atresia with a homograft aortic valve. Lancet 2: 1446, Seki, S., Rastelli, G. C., McGoon, D. C., and Titus, J. L. Replacement of pulmonary artery with a pulmonary arterial homograft.] Thorac Cardiovusc Surg 60:853, Wallace, R. B., Rastelli, G. C., Ongley, P. A., Titus, J. L., and McGoon, D. C. Complete repair of truncus arteriosus defects.] Thorac Cardiovusc Surg 57:95, Welton, C. S., Rowe, R. D., and Gott, V. L. Clinical experience with the use of aortic valve hoinografts for reconstruction of the pulmonary artery, pulmonary valve, and outflow portion of the right ventricle. Circulation 37 (Suppl. 11):51, Addendum Since this manuscript was submitted, Patient 8 was readmitted because of a marked change in his clinical condition. Physical examination revealed cyanosis, a harsh systolic murmur, and absent valve sounds. Cardiac catheterization showed pressure in the right ventricle and proximal conduit to be 130 systolic, equal to systemic. The catheter could not be advanced past the valve. Left ventricular saturation was SO%, revealing a marked right-to-left shunt through a recurrent ventricular septal defect. Reoperation was performed on October 14, The No. 19 Bjork prosthesis was found to be thrombosed in the open position and was removed. The Dacron conduit was closed end-to-end without a valve. The recurrent ventricular septal defect was closed primarily. Pressures measured in the operating room at the close of the procedure were: right ventricular, 75/20; distal conduit, 70/20; and aortic, 90/60. Because of these findings, cardiopulmonary bypass was reinstituted and an 18-mm woven Dacron tube containing a porcine valve (Hancock Laboratories) was inserted into the conduit. The immediate postoperative course has been satisfactory. 288 THE ANNALS OF THORACIC SURGERY