Jacques A. M. van Son, MD, V. Mohan Reddy, MD, Gary S. Haas, MD, and Frank L. Hanley, MD, San Francisco, Calif.

MODIFIED SURGICAL TECHNIQUES FOR RELIEF OF AORTIC OBSTRUCTION IN {S,L,L} HEARTS WITH RUDIMENTARY RIGHT VENTRICLE AND RESTRICTIVE BULBOVENTRICULAR FORAMEN Modified techniques of aortopulmonary anastomosis were performed in six neonates with atrioventricular and ventriculoarterial discordance {S,L,L}, double-inlet left ventricle, and restrictive bulboventricular foramen area (mean index 1.10 cmz/m 2) with unobstructed aortic arch (n = 3) or with hypoplasia (n = 2) or interruption (n = 1) of the aortic arch. In cases of unobstructed aortic arch, a flap of autogenous aortic tissue was used to augment the posterior aspect of the anastomosis of the main pulmonary artery to the ascending aorta, thus creating the potential for anastomotic growth; this technique is applicable regardless of the position of the ascending aorta relative to the main pulmonary artery. In case of ievotransposition of the aorta with hypoplasia or interruption of the aortic arch, a modified Norwood procedure was performed, in that the proximal ascending aorta was divided at the same level as the main pulmonary artery with subsequent homograft patch augmentation from the main pulmonary artery-ascending aorta anastomosis to the level of the proximal descending aorta; this technique avoids a spiraling incision of the aorta and therefore reduces the risk of torsion of the aortic root with its inherent risks of obstruction of the coronary circulation and aortic or pulmonary valve regurgitation. There was no early or late mortality. At a mean follow-up of 16 months, in all patients, there was unobstructed aortic outflow, as evidenced by echocardiographic absence of a significant ventricular-aortic systolic gradient (mean 4.5 -+ 4 mm Hg) and absence of distal aortic arch obstruction. There was no evidence of aortic or pulmonary valve regurgitation. The reported modified techniques provide effective relief of restrictive bulboventricular foramen and aortic obstruction in {S,L,L} hearts. (J THORAC CARDIOVASC SURG 1995;110:909-15) Jacques A. M. van Son, MD, V. Mohan Reddy, MD, Gary S. Haas, MD, and Frank L. Hanley, MD, San Francisco, Calif. bstruction of the bulboventricular foramen O (BVF), the communication between the left ventricle and the incomplete right ventricular outflow chamber, may complicate the clinical course of patients with double-inlet left ventricle (DILV) or tricuspid atresia and transposition of the great arteries. Although it may be difficult to determine whether the BVF is obstructed in neonates because of patency of the ductus arteriosus, it is well known From the Division of Cardiothoracic Surgery, UCSF, San Francisco. Calif. Received for publication Dec. 28, 1994. Accepted for publication March 17, 1995. Address for reprints: J. A. M. van Son, MD, Division of Cardiothoracic Surgery, UCSF, 505 Parnassus Ave., San Francisco, CA 94143-0118. Copyright 1995 by Mosby-Year Book, Inc. 0022-5223/95 $5.00 + 0 12/1/64936 that a BVF that is not restrictive in the neonatal period may become obstructed with time. All patients with a BVF index of less than 2 cm2/m 2 at neonatal age in whom early BVF bypass is not done have a high likelihood of BVF obstruction. 1 An attractive management option for restrictive BVF consists of an aortopulmonary anastomosis, that is, a Damus-Stansel-Kaye procedure 2-4 with construction of a modified Blalock-Taussig shunt in the presence of an unobstructed aortic arch or a Norwood stage! procedure in the presence of associated aortic arch obstruction. 5" 6 However, both types of aortopulmonary anastomoses can be technically awkward if transposed great vessels are present. In this report we review our experience with modifications of both techniques in neonates with levo-transposition of the great arteries, DILV, rudimentary right ventricular outflow chamber, and restrictive BVF, with and without aortic arch obstruction. 909

910 van Son et al. The Journal of Thoracic and October 1995 I I :S-i Fig. 1. Transthoracic two-dimensional echocardiogram from subcostal coronal view demonstrating heart with {S,L,L} segmental anatomy, DILV, and rudimentary right ventricle (asterisk) that communicates with left ventricle (LV) through restrictive BVF. PA, pulmonary artery; RA, right atrium. Patients and methods BVF is defined as a communication between a dominant left ventricle and rudimentary right ventricle (a remnant of the bulbus cordis) in a functionally univentricular heart with transposed great arteries. Rudimentary right ventricle is defined as an incomplete morphologically right ventricle that receives either no atrioventricular valve inflow or a minimal commitment of an overriding atrioventricular valve. Although the term BVF is not universally accepted, we prefer it to interventricular communication or ventricular septal defect because the term BVF has embryologic implications inasmuch as it refers to a communication between the left ventricle and a remnant of the bulbus cordis. DILV is considered present when the atrioventricular connection of both atria empties predominantly into the morphologically left ventricle. Between July 1992 and October 1994, six neonates (range 2 to 12 days, median 7 days) with situs solitus, atrioventricular and ventriculoarterial discordance {S,L,L}, DILV, restrictive BVF, and patent ductus arteriosus (Fig. 1) underwent operative treatment to prevent aortic outflow obstruction. In three patients the aortic arch was unobstructed; two patients had hypoplasia of the ascending aorta and aortic arch and one patient had type B interrupted aortic arch. Morphologic diagnosis was based on two-dimensional echocardiographic and angiographic evaluation. In all patients, the cross-sectional area of the BVF was calculated from the transverse and apex to base diameter of the BVF; BVF area was then indexed to body surface area as BVF area index. A restrictive BVF was defined as a BVF area index of less than 2 cm2/m 2. Ventricular volumes Fig. 2. Main pulmonary artery is transected just proximal to pulmonary artery confluence. LongitUdinal incision in ascending aorta extends from base of innominate artery to level of rim of transected main pulmonary artery. Second incision in aorta runs perpendicular to first one, thus creating flap of autogenous aortic tissue. were measured, normalized to body surface area, and expressed as percent of normal mean value. 7' s Myocardial mass measurements were made from ventricular volume and myocardial wall thickness, normalized to body surface area, and expressed as percent of normal mean value. 9' lo All patients underwent intraoperative and serial postoperative echocardiographic studies. After operation, the blood pressure in both arms and legs was measured on several occasions. Operative technique. All operations are done through a midline sternotomy. When there is only mild aortic hypoplasia without aortic arch obstruction, the aorta is cannulated at the proximal arch level and a single venous cannula is placed through the right atrial appendage. After cardiopulmonary bypass is instituted both pulmonary artery branches are rapidly occluded. The patent ductus arteriosus is ligated. The baby is cooled on bypass to 28 C while esophageal, nasopharyngeal, and rectal temperatures are being monitored. The ascending aorta is crossclamped immediately proximal to the innominate artery and cardioplegic solution is administered through the aortic root. The pulmonary artery is transected adjacent to the takeoff of the right pulmonary artery, and the pulmonary artery confluence is closed with a pulmonary homograft patch. The ascending aorta is incised longitudinally from a level just proximal to the innominate artery to the level of the rim of the transected proximal main pulmonary artery. Subsequently, a second incision is made into the aorta, perpendicular to the first one, parallel to the rim of the transected proximal main pulmonary artery (Fig. 2), thus creating a flap of autogenous aortic tissue

The Journal of Thoracic and Volume 110, Number 4, Part 1 van Son et al. 9 1 1 h ~< Fig. 3. After main pulmonary artery is anastomosed to ascending aorta, autogenous aortic flap is anastomosed to back wall of main pulmonary artery. (Fig. 3). After the medial aspect of the transected proximal main pulmonary artery is anastomosed to the medial aspect of the incised proximal ascending aorta, the aortic flap is anastomosed to the back wall of the proximal main pulmonary artery. All anastomoses are constructed with 7-0 polyglyconate suture (Maxon, Davis & Geck, Inc., Danbury, Conn.). The anterior defect between the pulmonary artery and aorta is augmented with a triangular pulmonary homograft patch. Finally, a 3 or 3.5 mm polytetrafluoroethylene (PTFE) tube graft* is constructed from the right subclavian artery to the pulmonary artery confluence (Fig. 4). When there is considerable hypoplasia of the ascending aorta and aortic arch (Fig. 5) or interrupted aortic arch, a modification of the Norwood operation is done. Cardiopulmonary bypass is instituted after cannulation of the proximal pulmonary artery and single venous cannulation; the pulmonary arteries are occluded. The patient is cooled by means of bypass to 15 C. During this time, the branch vessels of the aortic arch are exposed and looped with suture tourniquets. After circulatory arrest is established the head vessels are occluded, the main pulmonary artery is transected just proximal to the confluence, and its distal end is closed with a pulmonary homograft patch. The ascending aorta is divided at the same level. The ductus arteriosus is then exposed, ligated, and transected at its entrance into the descending aorta. In case of interrupted aortic arch (type B in this report), the proximal left carotid artery is anastomosed to the proximal left subclavian artery in a side-to-side fashion. Starting at the level of the transected ductus arteriosus, the hypoplastic aorta is incised distally approximately 1 cm into the descending aorta and proximally at the inner curvature of the aortic arch and at the medial aspect of the ascending aorta (Fig. *Gore-Tex brand, registered trademark of W. L. Gore & Associates, Inc., Elkton, Md. \v- Fig. 4. Pulmonary artery-aorta anastomosis is augmented with triangular pulmonary homograft patch. PTFE tube graft is constructed from right subclavian artery to pulmonary artery confluence. 6). The proximal main pulmonary artery is then anastomosed to the proximal ascending aorta over a distance of 2 to 4 mm (depending on the size of the aorta). A triangular pulmonary homograft patch is used to augment the incised aorta. Subsequently, the distal end of the transected distal ascending aorta with its homograft gusset is anastomosed end-to-end to the previously joined proximal ascending aorta and main pulmonary artery. Finally, a 3 to 3.5 mm PTFE shunt is constructed from the right subclavian artery to the pulmonary artery confluence (Fig. 7). Routine management for single ventricle physiologic conditions (including ventilation with CO2 to facilitate maintenance of a systemic/pulmonary flow ratio at or close to unity) is then used for the remainder of the intraoperative and postoperative course. Results The preoperative BVF area index in the six patients ranged from 0.82 to 1.52 cmz/m z (mean 1.10). None of the patients had a gradient detected across the BVF; in all patients the ductus arteriosus was widely patent. The mean thickness of the left ventricular posterior wall during diastole was 120% + 7% of normal. The mean left ventricular myocardial mass was 115% _+ 5% of normal and the mean left ventricular myocardial mass/volume ratio was 0.65 _+ 0.14. The three patients with unobstructed aorta underwent a modified pulmonary artery-aorta anastomosis. The two patients with aortic arch hypoplasia and th e patient with interrupted aortic arch underwent,

9 12 van Son et al. The Journal of Thoracic and October 1995 Fig. 5. Heart with {S,L,L} segmental anatomy, DILV, restrictive BVF, and hypoplasia of aorta proximal to ductus arteriosus. respectively, modified Norwood procedures and a modified Norwood procedure with aortic arch reconstruction. There was no early or late mortality and there were no complications related to the operations. At a mean follow-up of 16 months, all patients are free of symptoms. In all patients, there was complete relief of all levels of aortic outflow obstruction, as evidenced by echocardiographic absence of a significant ventricular-aortic systolic gradient (mean 4.5 _+ 4 mm Hg) and absence of a gradient across the distal aortic arch; in addition, there was no blood pressure gradient between arms and legs. There was no evidence of aortic or pulmonary valve regurgitation. Postoperative angiography at 4 months in one patient with a pulmonary arteryaorta anastomosis with autogenous aortic flap demonstrated a widely patent anastomosis (Fig. 8). Five patients have undergone and one is scheduled to undergo a bidirectional cavopulmonary shunt as an interim step to creation of a Fontan circulation. Discussion Subaortic stenosis is a risk at some stage in patients in whom the aorta arises from a rudimentary ventricle that communicates with a functionally single ventricle through a BVF. The development of BVF obstruction is associated with pressure over- Fig. 6. Main pulmonary artery is transected just proximal to pulmonary artery confluence. Ascending aorta is transected at same level. After ligation and transection of ductus arteriosus, hypoplastic aorta is incised along its inner curvature, from approximately 1 cm distal to transected ductus arteriosus to proximally transected ascending aorta. load, hypertrophy, and fibrosis of the functionally single ventricle. 11 The probability of its appearance is increased by smallness of the BVF and probably by the association of distal aortic arch obstruction. The mechanism of late obstruction in most cases is failure of the BVF to grow in proportion to somatic growth. 1 Subaortic stenosis can also be caused by obstruction within the outflow chamber 12 or encroachment of straddling atrioventricular valve tissue or other fibrous tissue on the BVF. 13 Other important factors associated with aortic outflow tract obstruction are the sudden ventricular unloading of the Fontan operation 14 and the effect of pulmonary artery banding. 15-17 Patients with an initial BVF area index of less than 2 cm2/m 2 as measured by biplane two-dimensional echocardiography are at high risk for the development of BVF obstructionj Several operations for the management of BVF obstruction have evolved through the years. First, a side-to-side aortopulmonary communication with distal main pulmonary artery banding resulted in the development of ventricular hypertrophy and dilation with ineffective control of the pulmonary circulation, which are unfavorable conditions for subsequent Fontan operation. 12 Second, enlargement of the BVF is a tech-

The Journal of Thoracic and Volume 110, Number 4, Part 1 van Son et al. 9 13 Fig. 7. Anastomosis of proximal main pulmonary artery with proximal ascending aorta is augmented with triangular pulmonary homograft patch. Pulmonary artery confluence is closed with pulmonary homograft patch. PTFE tube graft is constructed from right subclavian artery to pulmonary artery confluence. nically cumbersome procedure, especially in newborn infants, and entails a substantial risk of injury to the right cusp of the aortic valve and potentials for recurrent obstruction and myocardial dysfunction (when done through the rudimentary right ventricle); in addition, it does not relieve the obstruction caused by hypoplasia of the aortic anulus or beyond. 11'18-2 Most important, however, in hearts with {S,L,L} segmental anatomy this procedure carries a high risk of complete atrioventricular block because the nonbranching atrioventricular bundle courses at the superior-anterior margin of the BVF. 2l' 22 In contrast, resection of the infundibular septum through a right atrial approach is feasible in hearts with BVF and {I,D,D} segmental anatomy 23 and in exceptional hearts with {S,L,L} anatomy and posterior location of the atrioventricular node and bundle, 24 as is the case in selected patients with ventricular septal defect, subaortic stenosis as a result of posterior displacement of the infundibular septum, and aortic arch obstruction. 25 A third option, the arterial switch operation, converts aortic outflow tract obstruction into pulmonary outflow tract obstruction with generally an unpredictable outcome with regard to the amount of Fig. 8. Right anterior oblique view of angiogram 4 months after performance of anastomosis of pulmonary artery (PA) to aorta (Ao) augmented posteriorly with autogenous aortic flap and anteriorly with pulmonary homograft patch. pulmonary blood flow; consequently, an aortopulmonary shunt is often needed. 26' 27 Awareness of the serious side effects of BVF obstruction on the outcome of the Fontan operation has prompted the adoption of a policy of early palliation that is directed at relieving the obstruction in the newborn period even before the appearance of hemodynamically or anatomically significant stenosis, at protecting the pulmonary circulation, and at preventing the deleterious effects of chronic pressure or volume overload on the ventricle. As evidenced by the results of this study, at neonatal age, in the presence of a patent ductus arteriosus, the effects of an obstructive BVF on ventricular wall thickness are only minimal or absent. We believe, with others, 5' 28-30 that BVF obstruction in patients with DILV or tricuspid atresia with transposed great arteries is optimally managed by an aortopulmonary anastomosis with or without aortic arch reconstruction (depending on the presence or absence, respectively, of obstruction or interruption of the aortic arch) and construction of a modified Blalock-Taussig shunt. This approach bypasses all levels of obstruction to systemic blood flow, whether caused by BVF or hypoplasia of the aortic anulus and beyond. In addition, it provides limited, but adequate, blood flow to the pulmonary artery and therefore allows adequate systemic oxygenation, yet minimizes the

914 van Son et al. The Journal of Thoracic and October 1995 chance of development of pulmonary vascular disease. The presence of pulmonary valve regurgitation generally is a contraindication to performance of an aortopulmonary anastomosis; in this case, enlargement of the BVF may be the best alternative option. The technical modifications as applied in this small series of patients with levo-transposition of the aorta, rudimentary right ventricle, and restrictive BVF resulted in a wide unobstructed connection between the functionally single ventricle and aorta. The contribution of autogenous aortic tissue to the pulmonary artery-aorta anastomosis in cases with unobstructed aortic arch allows for growth of the anastomosis and prevents tension on the suture line or distortion of the semilunar valves and coronary ostia. Another advantage of this modification is that it avoids an extensive anastomosis on the posterior surface of the ascending aorta with its inherent risk of bleeding. This technique is applicable regardless of the position of the ascending aorta relative to the main pulmonary artery. When the ascending aorta is levo-transposed and severely hypoplastic, which is almost always accompanied by hypoplasia or interruption of the aortic arch, complete transection of the ascending aorta and augmentation of the hypoplastic aortic segment with a pulmonary homograft patch (and reconstruction of interrupted aortic arch if present), as reported here, avoids a spiraling incision of the aorta (from the inner curvature of the aortic arch to the posteromedial aspect of the ascending aorta). This modification reduces the risk of torsion of the aortic root with its inherent risks of obstruction of the coronary circulation and aortic or pulmonary valve regurgitation. REFERENCES 1. Matitiau A, Geva T, Colan SD, et al. 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