Asian Cardiovasc Thorac Ann 2002;10:235-239
© 2002 Asia Publishing EXchange Pte Ltd
Two-Stage Arterial Switch Operation: is Late Ever Too Late?
Howaida O Al Qethamy, MD,
Khawar Aizaz, FRCSI,
Saber AR Aboelnazar, MD,
Samina Hijab, MBBS,
Yahya Al Faraidi, MD
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Department of Cardiac Surgery Prince Sultan Cardiac Centre Riyadh Military Hospital Riyadh, Saudi Arabia
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For reprint information contact: Khawar Aizaz, FRCSI Tel: 966 1 467 9353 Fax: 966 1 467 1581 email: kzazs{at}yahoo.com Department of Cardiac Surgery (F-277), Prince Sultan Cardiac Centre, Riyadh Military Hospital, P.O. Box 7897, Riyadh 11159, Saudi Arabia.
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ABSTRACT
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Results of the two-stage arterial switch operation in 49 patients with transposition of the great arteries, performed between January 1995 and September 2000, were reviewed retrospectively. Twenty-one patients had a ventricular septal defect. Anatomical correction was carried out 21.89 ± 9.86 months after pulmonary artery banding, with or without a modified Blalock-Taussig shunt. Hospital mortality was 8% (4 patients). During follow-up of 30.12 ± 14.38 months, there was 1 late death and 1 patient required reoperation for pseudoaneurysm of the ascending aorta. Actuarial survival and freedom from reoperation at 5 years were 90% and 97%, respectively. Late anatomic correction (> 6 months) after the preliminary procedure can be performed with an acceptable mortality and morbidity, but undue delay may lead to left ventricular dysfunction, arrhythmias, and new aortic valve regurgitation or subaortic stenosis.
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INTRODUCTION
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An arterial switch operation (ASO) should preferably be undertaken within the first 2 weeks of life in cases of transposition of the great arteries with an intact ventricular septum or a restrictive ventricular septal defect.1 Beyond this period, there is increasing likelihood that the left ventricle will be unable to accommodate the acute increase in workload due to systemic pressure. Patients with transposition of the great arteries and a ventricular septal defect can undergo an elective ASO within the first 2 months of life. Severe illness secondary to necrotizing enterocolitis, renal or hepatic failure, birth weight less than 2 kg, or delayed presentation can result in post-ponement of surgery beyond the accepted safe period.2 An ASO after a preliminary procedure such as pulmonary artery (PA) banding, with or without a Blalock-Taussig shunt, to prepare the left ventricle is an option for these children. An interval of 7 days to 8 months between the preliminary procedure and the ASO has been reported.3–5 This study reviews our experience and midterm results with the two-stage ASO.
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PATIENTS AND METHODS
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Between January 1995 and September 2000, 49 patients underwent a two-stage ASO. A balloon atrial septostomy was performed at the initial catheterization in patients with a patent foramen ovale or restrictive atrial septal defect at the time of presentation. The mean left ventricular (LV) to right ventricular (RV) pressure ratio before the first-stage procedure was 0.52 ± 0.8, and LV posterior wall thickness was 3.52 ± 0.28 mm. Clinical data are summarized in Table 1
. M-mode and 2-dimensional echocardiography was carried out before the first stage in all patients. Preliminary preparatory procedures were performed via a left thoracotomy. A modified Blalock-Taussig shunt was usually constructed using a 4-mm polytetrafluoroethylene tube prior to PA banding with a nylon tape around the main PA (according to Trussler’s formula) to achieve LV pressure of 75% of the systemic pressure (as measured by a pressure catheter inserted through a pursestring suture in the distal PA).6 The pericardium was then closed leaving a pericardial window.
The ASO was performed at 21.89 ± 9.86 months after preliminary PA banding. The mean age was 36 ± 21.31 months at the time of the definitive repair (Table 1
). In general, the procedures were performed via a median sternotomy. Adhesions rarely presented a serious problem. Cardiopulmonary bypass was initiated via aortic and bicaval venous cannulation. The Blalock-Taussig shunt was clipped prior to going on cardiopulmonary bypass. An aortic crossclamp was applied, followed by a single dose of 25 mLákg–1 of cold blood cardioplegia, and cooling to 25°C. Circulatory arrest was not used in any of these patients. The coronary ostia were excised along with a large segment of surrounding aortic wall, extending the incision well into the base of the sinus of Valsalva. The proximal coronary arteries were mobilized sufficiently to avoid tension or kinking. The PA was divided, the band was removed, and the Lecompte maneuver was carried out. A similar U-shaped segment of arterial wall was removed from both the left and right anterior aspects of the native proximal PA, to allow coronary implantation. The aortic anastomosis was carried out, and intracardiac defects (ventricular or atrial septal defects) were repaired via the right atrium. After closing the right atrium, the heart was deaired and the aortic crossclamp was removed. Coronary explantation sites in the new PA were filled using a single long inverted bifurcated patch of autologous pericardium. This new proximal PA was anastomosed to the distal PAs. The patient was weaned from cardiopulmonary bypass, and the operation was completed in the usual fashion. The coronary anatomy in these patients is outlined in Figure 1.
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Figure 1. Coronary anatomy in 49 patients requiring an arterial switch operation. LAD = left anterior descending artery, LCA = left coronary artery, LCx = left circumflex artery, RCA = right coronary artery.
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The criteria used to judge the readiness of the left ventricle to support systemic circulation included LV/RV peak pressure ratio of 70% or more and LV posterior wall thickness equal to or more than the predicted normal value for age. The LV wall thickness was estimated from the M-mode echocardiogram according to the recom-mendation of the American Society of Echocardiography.7
Nonparametric non-risk-adjusted estimates of freedom from events were obtained by the method of Kaplan and Meier.8 Data were compared and tested for statistical validity by paired Student’s t test; p values < 0.05 were considered significant. Unless otherwise specified, all values are expressed as mean ± standard deviation.
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RESULTS
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The hospital mortality was 8% (4 patients). Mortality in 3 cases could be related to the coronary anastomosis. One patient had an intramural left coronary artery and was unable to come off bypass, 2 died on the first postoperative day secondary to intractable arrhythmias, and the other developed renal failure followed by septicemia from which he did not recover. The operative results and complications are detailed in Table 2. Two-dimensional echocardiography was performed in all patients before discharge. Normal LV regional and global function was found in all patients, trivial aortic regurgitation was detected in 3, there was mild pulmonary regurgitation in 2, and none had a significant gradient across the aortic and pulmonary anastomosis.
For all 45 hospital survivors, follow-up data was available from the records of clinical examination and echo-cardiography documented at the time of the last visit to the outpatient clinic. There was one late death which occurred 42 months after the ASO; the details of this death were not recorded. The remaining 44 patients were followed up for a mean period of 30.12 ± 14.38 months. One patient required reoperation for pseudoaneurysm of the ascending aorta 49 months after the ASO. Intraoperative findings were supracoronary dehiscence of the aortotomy suture line. Repair was carried out with an interposition graft, and the patient made an uneventful recovery. The actuarial survival and freedom from reoperation at 5 years were 90% and 97%, respectively (Figures 2 and 3). Two patients had a moderate degree of aortic regurgitation and were in New York Heart Association functional class II or III; the others were in New York Heart Association functional class I with no significant aortic or pulmonary valve pathology.
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Figure 2. Kaplan-Meier survival curve (solid line) with 95% confidence limit (dashed line) for 45 patients followed up after a two-stage arterial switch operation.
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Figure 3. Kaplan-Meier freedom from reoperation curve (solid line) with 95% confidence limit (dashed line) for 45 patients followed up after a two-stage arterial switch operation.
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DISCUSSION
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Primary anatomical correction is the optimal treatment for transposition of the great arteries in the neonatal period.9 However, a two-stage ASO is the best option for patients who, for reasons of size or sickness in the neonatal period cannot be offered primary correction; after the first weeks of life, approximately half of the infants with transposition of the great arteries and an intact ventricular septum have a left ventricle incapable of sustaining systemic arterial pressure.10 The ideal interval between the preliminary preparatory procedure and anatomical correction has been a matter of debate because the definition of a well-prepared left ventricle has been unclear. Nakazawa and colleagues11 defined a prepared left ventricle as: LV/RV pressure ratio > 0.85, LV end-diastolic volume > 90% of normal, LV ejection fraction > 40%, posterior wall thickness > 4 mm, and predicted wall stress < 120 x 103 dyneácm-2; they performed a two-stage ASO in 35 patients fulfilling these criteria, with a mean interoperative period of 8 ± 6.8 months, and hospital mortality of 8%.
Cardiac hypertrophy secondary to PA banding is accompanied by transient depletion of adenosine triphosphate and a decrease in deoxyribonucleic acid relative to cell volume, thereby leading to transient depression of LV function, which has been of concern to us and other authors.4,5,12 Intervals of 5 to 8 months between the two operative stages have been described.5,13 In addition, there is a tendency for the band pressure gradient to decrease after 2 to 3 months because of remodeling of the fold of the PA wall, due to the band.13 This can result in an inadequate pressure load on the left ventricle. Therefore, we aimed to undertake anatomical repair approximately 6 months after the initial preparation. Excessive delay beyond this period was due to parental noncompliance and administrative problems beyond our control. Experimental studies in rats have shown that banding the ascending aorta produces an increase in heart weight and ribonucleic acid within 48 hours.14 In view of this, Jonas and colleagues3 adopted intervals of 7 to 10 days in 11 patients, with no operative mortality but one late death, suggesting that the left ventricle became prepared within a short period. These results were encouraging, but fell short of defining the criteria for timing the second operative stage.
Although long-term survival after an atrial switch operation is acceptable, there is a 10% incidence of RV dysfunction and a 50% incidence of atrial dysrhythmia within 10 years of the operation.15 Moreover, in the majority of patients, RV function shows an abnormal response to afterload as early as one year postoperatively.16 Because of its anatomical and physiological advantages, PA banding with or without a Blalock-Taussig shunt, followed by an ASO, may afford better results in patients who present beyond the neonatal period. In this series, the LV/RV pressure ratio and LV wall thickness were used to assess readiness of the left ventricle to support the systemic circulation. Clinical studies have shown poor LV performance after ASO in patients with subnormal muscle thickness despite high LV pressure.17 Although these results show that an ASO can be performed late (> 6 months), even years after initial palliation, with an acceptable mortality and morbidity, we would like to stress that undue delay can result in extensive LV hypertrophy leading to LV dysfunction, arrhythmias, and new aortic valve regurgitation and subaortic stenosis.18–20
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ABSTRACT
INTRODUCTION
