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Ann Thorac Surg 1998;66:2082-2084
© 1998 The Society of Thoracic Surgeons
a University Hospital Groningen, Hanzeplein, 1, Postbus 30.001, 9700RB Groningen, The Netherlands
Invited commentary
The paucity of articles on clinical results describing the repair of the combination of atrioventricular septal defects and tetralogy of Fallot is not in keeping with the reported incidence of this anomaly, said to be present in 5% to 10% of all patients with atrioventricular septal defect. The first article reporting successful corrective operation for this anomaly to my knowledge was by d’Allaines and colleagues [1] from Paris in 1969, who reported on 2 patients, who were 16 and 18 years old, who had a Blalock-Taussig shunt at 4 years and 4 months, respectively. The first survived the corrective procedure, the second died after pulmonary valvotomy [1]. Rastelli and associates [2] reported on 2 patients who were operated on for atrioventricular septal defect and were severely cyanotic because of associated valvular and infundibular stenosis; both died. The article by O’Blenes and associates in this issue of The Annals of Thoracic Surgery, in which they report excellent results in 11 patients, is a significant addition to our scientific knowledge of this anomaly; the mortality of just 1 patient is outstanding (9.1%). The largest published series includes 35 patients who were operated on from 1980 to 1995; 29 of these patients underwent a definitive operation with an operative mortality of 10.3% [3]. A further series of 21 such patients was hidden in a Toronto report on 363 children with atrioventricular septal defects [4]. The lack of more articles on larger numbers of patients can be explained either by publication bias or by selection of patients. Publication bias plays a role when results are worse than what is perceived to be acceptable, so that clinicians feel disinclined to publish. It is notable that case reports on failures are singularly absent, whereas they can be found on successes. Selection of patients could play a role when operation is deemed unsuitable because of natural palliation, with the pulmonary stenosis counterbalancing the potential shunt, in the setting of fairly well functioning atrioventricular valves. Down’s syndrome is present in approximately 75% of these patients, which to some clinicians is a further argument against repair. In fact, these patients can be only mildly symptomatic. However, when operative results are as good as reported by O’Blenes and coauthors there is little reason to withhold corrective operations from Down’s syndrome children, because their exercise capacity and, thus, quality of living can only improve. Improvement then shall be at the cost of a reasonable mortality, which is decreasing during the years with growing experience.
Previously, the generally accepted policy was to palliate with an aortopulmonary shunt in case of cyanosis, and repair only after the age of 4 years, because the repair was easier in a larger patient and thus mortality was reduced [5]. In the past decade, however, the general tendency has been to perform complete repair of atrioventricular septal defect in infancy, and the same trend of a lowering age threshold is now emerging in the setting of atrioventricular septal defect associated with tetralogy of Fallot. O’Blenes and associates palliated 9 of 11 patients with a shunt and performed an additional pulmonary valvotomy in one. Although 2 patients underwent corrective operations without palliation, at 7 and 12 months of age, these patients were not at the end of the series. Median age at repair was 33 months, without noticeable descent of age during the years. The surgeons of Great Ormond Street reported operating on 14 patients without prior palliation, the selection for this strategy being made on the basis of miscellaneous anatomic factors and personal preference. It has to be borne in mind that mortality in the palliated group was 3 of 21 patients, making for a mortality of 14.3%, which has to be included in the mortality of the total treatment. Because the study by O’Blenes and coworkers only deals with patients having undergone corrective operation, it is unknown to us what the mortality was in the palliated group before attempts at corrective procedures.
Whether catheterization is currently indicated in all patients is doubtful, unless exclusion of a coronary artery running in front of the right ventricular outflow tract is the object. Even then, operation is not contraindicated; the surgeon will just have to resort to measures other than a transannular outflow patch to alleviate obstruction at that level. An extracardiac conduit is then an obvious solution. Otherwise I see no indication for catheterization, Doppler echocardiography being perfectly capable of delineating cardiac morphology and physiology in the hands of an experienced echocardiographist.
Recent anatomic studies indicate that the aorta is dextraposed in all patients with atrioventricular septal defect; however, when tetralogy of Fallot is associated, the aorta, overriding the superior portion of the ventricular septal defect, is dextraposed to an even greater degree, so that the majority overrode the septum for more than 50%, making it a double outlet right ventricle [6]. The aorta is not wedged between the mitral and tricuspid valves as in normal hearts, but instead is "unwedged" and located anterior to the common atrioventricular valvular apparatus, a feature that is pathognomonic for atrioventricular septal defect. This unwedged aorta produces the long and narrow left ventricular outflow tract in many patients with atrioventricular septal defect, unless the superior bridging leaflet is "free floating," meaning unattached to the ventricular septal crest, as in the so-called Rastelli C configuration of the superior leaflet, which is usually the case in Down’s syndrome and always the case in the combination with tetralogy of Fallot—always, that is, with the exception of Delius and associates [3], whose report of 4 cases with a Rastelli A and 1 with a B configuration is the only one, which is hard to understand in this anomaly. In the Rastelli C configuration, when in systole the superior leaflet of the atrioventricular valve is pushed toward the atrium, the outflow tract is opened widely before correction. The ventricular patch, inserted during corrective operation, however, can then create a narrow outflow tract when the patch is too small anteriorly, because it constitutes the right-hand wall of this very outflow tract. Care must be taken to make this patch wide enough and to suture it far enough to the right to avoid creating outflow tract stenosis. When a good overview of the anatomy is difficult, which is not unusual, a Hegar sizer can well be inserted through the aortic valve into the left ventricle, after opening the ascending aorta, so as to sculpt the superior part of the patch around the sizer. This is a certain way to avoid iatrogenic outflow tract stenosis, which can be a serious problem, specifically in the immediate postoperative period.
In keeping with the trend toward earlier corrective repair for both tetralogy of Fallot and atrioventricular septal defect, it is to be expected that the same development will take place in the combination of the two. Surgical skills are still improving, and most pediatric surgeons are now used to performing delicate operations such as the neonatal arterial switch operations for transposition of the great arteries. Within the coming years, reports are to be expected on infant and neonatal repair of the anomaly under discussion. O’Blenes and coauthors have given us an excellent addition in that trend. [7]
References
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