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Ann Thorac Surg 1999;68:962-967
© 1999 The Society of Thoracic Surgeons
a Division of Cardiothoracic Surgery, University of California, Los Angeles Medical Center, Los Angeles, California, USA
b Division of Pediatric Cardiology, University of California, Los Angeles Medical Center, Los Angeles, California, USA
Address reprint requests to Dr Laks, Division of Cardiothoracic Surgery, UCLA Medical Center, 10833 Le Conte Ave, Los Angeles, CA 90095
Presented at the Thirty-fifth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 25–27, 1999.
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Abstract |
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Methods. In 15 neonates (12 boys and 3 girls) with complex forms of single-ventricle pathology and aortic coarctation or interruption, an initial strategy of banding the pulmonary artery and repair of the obstruction from a left thoracotomy was undertaken.
Results. The median age at operation was 6 days (range 2 to 33 days) and the median weight was 3.3 kg (range 2 to 4.6 kg). There were no early deaths and one late death after the initial surgical palliation. Of the 14 survivors, 8 have undergone a bidirectional cavopulmonary anastomosis. The median age for bidirectional Glenn was 9.75 months (range 3.5 to 26 months). Seven infants have required Damus-Kaye-Stansel reconstruction for subaortic obstruction (one early death). The median age of the Damus-Kaye-Stansel procedure was 4 months (range 3 weeks to 9 months). Thirteen of 15 patients (87%) are alive and 6 have proceeded to a Fontan operation (median follow-up 68 months). A single failing Fontan required takedown to bidirectional Glenn and central shunt.
Conclusions. Our experience suggests that this high-risk subgroup of neonates with aortic obstruction and single-ventricle pathophysiology is safely managed by initial pulmonary artery banding palliation and repair of aortic obstruction. This strategy, careful surveillance, and early relief of subaortic stenosis can maintain acceptable anatomy and hemodynamics for later bidirectional Glenn and Fontan procedures.
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Introduction |
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The neonate with a single ventricle and aortic arch obstruction other than hypoplastic left heart syndrome poses a uniquely difficult challenge because of the stimulus for myocardial hypertrophy and failure from impedance to systemic outflow and pulmonary vascular disease from pulmonary overcirculation. In tricuspid atresia and double-inlet left ventricle with ventriculo-arterial discordance, the muscular bulboventricular foramen (BVF) presents yet another potential site of obstruction (subaortic) between the functional single ventricular pump and the systemic circulation. The regulation of pulmonary blood flow and pressure by banding the pulmonary artery in this setting narrows the BVF acutely, by volume unloading, and chronically, by muscular hypertrophy induced by the band. The ventricular hypertrophy caused by persistent obstruction of the systemic pathway alters diastolic function that may adversely affect long-term outcome.
A number of approaches have emerged to avoid subaortic stenosis, ventricular dysfunction, and the morbidity associated historically with pulmonary artery banding (PAB). These strategies include an initial modified Norwood procedure with circulatory arrest or an aorto-pulmonary connection (Damus-Kaye-Stansel) (DKS) on cardiopulmonary bypass. Pulmonary blood flow is then provided by a systemic-to-pulmonary artery shunt or a bidirectional cavopulmonary connection as appropriate.
This report reviews the early and mid-term outcome in a subset of neonates with univentricular physiology and aortic obstruction who, in addition, possess the substrate at highest risk for developing subaortic obstruction. These patients were initially managed by off-pump repair of the aortic obstruction plus short-term pulmonary artery banding en route to the ultimate goal of a Fontan procedure.
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Patients and methods |
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Subclavian flap angioplasty was used for aortic coarctation repair in all cases except 1, who underwent a coarctectomy with end-to-end anastomosis. Similarly, subclavian flap angioplasty was used for the neonates with type A interruption of the aortic arch. Concomitant left common carotid angioplasty and reverse left subclavian artery angioplasty techniques were used for associated arch hypoplasia. Two patients underwent left common carotid artery flap augmentation for accompanying arch hypoplasia. Two neonates with interrupted aortic arch were reconstructed with synthetic Gore-Tex grafts. This was in the early experience and both neonates were clinically unstable at time of repair.
The pulmonary artery bands were tightened to achieve a distal pulmonary artery pressure 30% to 50% of the systemic blood pressure while maintaining systemic oxygen saturations of 85% to 90% on a fraction of inspired oxygen concentration of 0.50.
The DKS operation was chosen to bypass the subaortic region when the BVF became restrictive. This procedure was performed using single aortic and bicaval cannulation with moderate hypothermia and low-flow cardiopulmonary bypass. Myocardial protection was achieved using antegrade and retrograde intermittent cold blood cardioplegia. Topical cooling was also used. After arch reconstruction, the myocardium were reperfused using substrate-enriched warm blood cardioplegia. The main pulmonary artery trunk is transected and anastomosed to a triangular-shaped aortotomy augmented with an autologous glutaraldehyde-treated pericardial patch reinforced with Dacron mesh [1]. Six infants in whom DKS was performed early after PAB had a Gore-Tex shunt placed between the innominate-subclavian artery junction to a branch pulmonary artery to supply the pulmonary circulation. Two children well outside the neonatal period during DKS performance had a bidirectional Glenn shunt or Fontan procedure at the same operation.
Six children have attained the ultimate surgical goal: a Fontan circulation. A modified lateral tunnel Fontan with snare adjustable atrial septal defect (ASD) was performed. Details of the operative techniques are presented elsewhere [2].
Data
Patient clinical charts, operative and diagnostic reports of cardiac catheterization, and echocardiograms were reviewed retrospectively. Follow-up was conducted by direct contact with referring physicians or patients and their families.
A restrictive BVF is defined by a measurable Doppler gradient from the dominant ventricle to aorta or a ventricular septal defect (VSD) that appeared less than half the size of the aortic annulus.
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Results |
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Mortality
Two out of 15 (13.3%) children (2 per 1,000 person-months of follow-up; approximate 95% confidence intervals, 0 to 4.8) have died.
An infant with a single ventricle of right ventricular (RV) morphology and a rudimentary left ventricle (LV) giving rise to the aorta via a VSD, mitral atresia, and coarctation died after DKS for subaortic stenosis. The immediate postnatal period was notable for lethargy, cyanosis, and jaundice. The patient had important hepatic and renal dysfunction and was transferred to our institution for management. At 6 days of age, after cardiac catheterization and balloon atrial septostomy, this neonate underwent an initial repair of the coarctation, pulmonary artery banding, and ligation of a patent ductus arteriosus (PDA). Four months later, he presented with systemic outflow obstruction (40 mm Hg peak systolic gradient), elevated systemic ventricular end-diastolic pressure (15 mm Hg), and a tight PAB (90-mm Hg peak systolic band gradient), and underwent urgent DKS and a systemic-to-pulmonary artery (PA) shunt. The patient suffered a cardiac arrest in the postoperative period secondary to pulmonary overcirculation, from which he was unable to recover despite narrowing the shunt. Postmortem examination was notable for a dilated systemic RV. There was medial hyperplasia of the pulmonary arterioles indicating pulmonary vascular disease and pulmonary congestion. This patient was the first in the series and was not aggressively followed up for early signs of a restrictive BVF.
Another child with an unbalanced complete arterio-venous (AV) canal (LV hypoplasia), moderate AV valve regurgitation, aortopulmonary (AP) window, aortic coarctation, and subaortic stenosis underwent repair of coarctation of the aorta and bilateral branch pulmonary artery banding at 10 days of life. The child continued to have some respiratory difficulties despite extubation and feeding, and 2 weeks later, underwent cardiac catheterization to assess AV valve regurgitation. An AP window was not confirmed on that study. The intraatrial and intraventricular communications were unrestrictive. Bilateral branch pulmonary artery bands were tight. There was severe tricuspid regurgitation. The patient returned to the operating room for removal of the branch pulmonary artery bands and placement of a proximal single band about the main pulmonary arterial trunk. The patient was discharged home after a brief episode of sepsis. She expired at 2.5 months of age after a brief illness at home.
Follow-up
These children have been followed up for a median of 69.1 months (range 0.2 to 164.4 months).
Three infants (3 per 1,000 person-months of follow-up; approximate 95% confidence intervals, 0 to 6.4) have developed semilunar (pulmonary) valve insufficiency The severity of pulmonary regurgitation was graded mild after PAB and DKS in all 3 children. Two of the children have undergone a Fontan operation and 1 underwent a BDG.
An additional 3 children have mild systemic AV valve regurgitation (3 per 1,000 person-months of follow-up; approximate 95% confidence intervals, 0 to 6.4).
Three infants developed recurrent aortic arch gradients after initial repair for aortic interruption (3 per 1,000 person-months of follow-up; approximate 95% confidence intervals, 0 to 6.4). Two infants had successful relief of their gradient after balloon angioplasty. One patient was lost to follow-up with an arch gradient of 15 mm Hg.
One patient (1 per 1,000 person-months of follow-up; approximate 95% confidence intervals, 0 to 2.9) developed a 35-mm Hg gradient across the DKS anastomosis that was successfully eliminated after balloon angioplasty.
A single patient contracted hepatits B during the course of a lateral tunnel Fontan procedure, and 1 year later, has developed a cardiomyopathy with arrhythmias and is being evaluated for possible heart transplantation. One patient developed third degree heart block 6 years after lateral tunnel Fontan and required dual chamber (DDD) pacemaker implantation. The remaining patients are awaiting evaluation for Fontan.
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Comment |
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Neonates born with a univentricular heart and aortic obstruction pose a particular surgical challenge, as the natural history without intervention is dismal and the surgical strategies that have evolved have been associated with high morbidity and mortality historically [5]. Because these patients with aortic obstruction and single-ventricle physiology usually have a large pulmonary artery and luxuriant flow, early surgical efforts addressed the preservation of the pulmonary vascular bed by constricting the main pulmonary arterial trunk with a band and repairing the aortic obstruction. Several investigators subsequently reported the development of subaortic stenosis that ultimately jeopardized Fontan candidacy [6–8]. This phenomenon was particularly unique to transposition complexes (double inlet left ventricle [DILV] and tricuspid atresia [TA]) with a systemic outflow from the dominant ventricle conducted via a VSD (restrictive bulboventricular foramen) and muscular infundibular chamber to the aorta. Other mechanisms of subaortic obstruction due to a restrictive subaortic conus (double outlet right ventricle [DORV]) or AV valve tissue (unbalanced AV canal) are observed in single-ventricle arrangements. The PAB was implicated in the accelerated development of subaortic obstruction secondary to muscular hypertrophy and restriction of the VSD and subaortic area [6–8]. Ventricular hypertrophy, large muscle mass, and reduced compliance have been identified as risk factors for successful Fontan hemodynamics. The work from Norwood and his group has elegantly demonstrated that volume-unloading procedures including pulmonary artery banding acutely precipitate geometric changes in the ventricle heralded by smaller cavity and increased wall thickness, compromising the systemic pathway [9]. Thus, it is probable that at least these two underlying mechanisms in the univentricular heart (myocardial hypertrophy and volume unloading) are responsible for the emergence of subaortic obstruction after PAB. Other complications associated with a poorly positioned band or migration were reported, including branch pulmonary stenoses, semilunar valve insufficiency, and erosion with aneurysm formation. These observations, noted after longstanding PAB, have threatened this palliative procedure with obscurity. But, recent reports in the current surgical era employing PAB for short-term purposes have demonstrated a substantial reduction in morbidity and mortality.
Jensen and colleagues [10] reported their results of initial PAB (with or without aortic arch reconstruction) in 26 infants with DILV or TA and transposed great arteries. A third of the group had associated obstructive arch abnormalities. There were no deaths after PAB with or without arch repair. An important subaortic gradient (defined as a resting gradient between the ascending aorta and left ventricle equal to or greater than 10 mm Hg) developed in more than half (16/26) of the patients. Nineteen infants, including an additional 3 without subaortic stenosis, underwent DKS (12 infants) or VSD enlargement (8 infants), alone or with a Glenn (14 infants) or Fontan procedure (15 infants). There were no deaths after 14 Glenn shunts, 6 (43%) of whom had simultaneous relief of subaortic obstruction. There were five hospital deaths during the study period (mortality rate of 19%).
Webber and associates, following a similar strategy of short-term PAB and early relief of subaortic stenosis, in 18 consecutive patients with DILV/TGA and an obstructive anomaly of the aortic arch (4 had subaortic stenosis), observed one death after PAB and arch repair [11]. A single patient with subaortic stenosis died after initial early aortopulmonary bypass. All but one of the 16 survivors developed subaortic stenosis and underwent a proximal aortopulmonary connection, with two early and one late death. Twelve of the 13 remaining survivors have attained a Fontan or Glenn repair.
Amin and associates have recently demonstrated the initial PAB for short-term palliation in this subset of patients does not cause important semilunar valvular insufficiency precluding later DKS in patients requiring management of subaortic stenosis [12]. In their retrospective review of 15 patients with single-ventricle physiology and systemic outflow obstruction, there was no operative mortality associated with primary PAB or later DKS. There were minimal PAB-related complications. Half of their patients attained a Fontan circulation during the study period. These recent reports are consistent with our findings that initial short-term PAB in this population is associated with very low mortality. Aggressive surveillance for detection of subaortic stenosis prompts earlier relief of systemic outflow obstruction and the stimulus for ventricular hypertrophy outside the vulnerable neonatal period, allowing many of these patients to proceed to successful Fontan.
The deleterious effects of irreversible myocardial hypertrophy on Fontan eligibility or attrition, though, has prompted surgical strategies seeking early initial relief of aortic obstruction and the avoidance of PAB. Karl and associates [13] and Lacour-Gayet and associates [14] have advocated a palliative arterial switch operation in newborns with univentricular morphology and subaortic stenosis trading subaortic for neo-subpulmonary stenosis. This approach has yielded unpredictable pulmonary blood flow requiring a later systemic source (shunt) or banding in the event of too much pulmonary blood flow. The reported numbers of patients undergoing this palliative one-stage arterial switch is low, the follow-up is short, and the ultimate suitability for Fontan operation is undetermined.
A direct attack by muscular resection and enlargement of the bulboventricular foramen or VSD to relieve subaortic obstruction has led to instances of postoperative heart block, ventricular dysfunction, and late aneurysm formation—all adverse conditions for optimal Fontan performance [15]. LV apical to aortic conduits, designed to bypass the subaortic area, lack long-term durability due to valvular degeneration and distortion with somatic growth of the child [16].
Damus [17], Kaye [18], and Stansel [19] independently described a procedure designed for surgical correction of transposition of the great vessels without coronary transfer that has been applied by many investigators to bypass actual or imminent subaortic obstruction. This extracardiac aortopulmonary bypass procedure requires provision of a reliable source of pulmonary blood flow via systemic to PA shunt, bidirectional cavopulmonary anastomosis, or total cavopulmonary connection (Fontan) as dictated by the clinical circumstances. Other workers have accomplished this goal with a modified Norwood procedure requiring a period of circulatory arrest.
Brawn and associates [20] reported nine early deaths in a series of 24 infants with complex forms of single-ventricle physiology and systemic outflow obstruction managed with initial modified Damus plus a 3.5-mm aortopulmonary shunt (early mortality rate of 38%). Ten of the 15 survivors underwent Glenn shunt, with one death during the study period (overall mortality rate of 42%).
McElhinney and associates have recently reported the outcome of DKS in 21 patients with univentricular physiology and subaortic obstruction, 15 of whom had concomitant arch obstruction [21]. All 17 patients in whom the DKS procedure was performed as a primary palliation had a 3- or 3.5-mm systemic-to-PA shunt. Three additional patients beyond the neonatal period underwent concurrent bidirectional Glenn shunt. The early mortality rate was 19%. There were no late deaths during the study period (median follow-up 33 months). Nine of the 17 survivors have undergone bidirectional Glenn shunt, including 3 attaining a Fontan. An additional patient received a cardiac allograft secondary to cardiomyopathy.
The results for the modified Norwood procedure in this subpopulation of infants without hypoplastic left heart syndrome have improved over time, particularly in centers with high volume and experience [22, 23]. Mosca and associates reported a remarkable early mortality of 8% in a group of 38 patients with tricuspid atresia or double-inlet LV and VA discordance undergoing a modified Norwood operation [24]. The majority (92%) of these infants had aortic arch anomalies. There were five late deaths (13.1%). Thirty percent and 60% of the surviving patients had undergone a hemi-Fontan and Fontan procedure, respectively.
The initial palliative approach described in this paper highlights the low mortality and morbidity of short-term pulmonary artery banding and aortic arch repair without cardiopulmonary bypass in a difficult constellation of neonates born with single-ventricle pathophysiology and obstruction of systemic outflow. It appears that the majority of neonates in this subclassification can undergo PAB regardless of the actual measurement of bulboventricular area index. On the basis of Matitiau’s findings in patients with univentricular physiology and aortic arch obstruction, one would predict an earlier tendency towards subaortic obstruction in our cohort of neonates [25].
Thus, the imminent development of subaortic obstruction is aggressively sought out after PAB and corrected with DKS and a controlled source of pulmonary blood flow. This avoids the potentially irreversible effects of chronic pulmonary artery banding on myocardial muscle mass and ventricular compliance. This strategy preserves Fontan eligibility. The spectrum of morphology in infants with functional single ventricle and variable degrees of aortic arch obstruction precludes the recommendation of one surgical strategy over another. Case-by-case application of alternative approaches seems most appropriate based on clinical outcome and institutional experience. The long-term neurodevelopmental effects of circulatory arrest employed in the staged Norwood approach or the low-flow cardiopulmonary bypass technique in the DKS strategy in neonates remain unanswered. On the other hand, the low incidence of semilunar valve insufficiency, branch pulmonary stenosis, and mortality indicate that short-term banding of the pulmonary artery is at the very least comparable with the more radical surgical approaches for the univentricular heart designed to avoid the issue of subaortic obstruction. The long-term effects on Fontan eligibility or suitability are not answered by this study but compare with the other strategies in the short-term.
Limitations
This report has focused on results of a single treatment strategy at a single center. In the subpopulation of neonates studied with univentricular hearts, the sample size is small because we reviewed our experience in those children born with aortic arch obstruction and thus, additionally, a high likelihood of having imminent subaortic obstruction. Limitations include wide variability in pathologic diagnosis, lack of prospective randomization, and an inability to discern what characteristics might favor one surgical strategy over another.
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