Conclusions
In this retrospective study we compared the early, late and overall occurrence of arrhythmias in adult and pediatric patients who underwent surgical repair of PAPVC + sinus venosus ASD over a thirty-years period. Nearly all patients were treated by means of single-patch and double-patch surgical technique (42.6% and 56.5% respectively). The incidence of transient and permanent arrhythmias in relation to the age at repair and to the type of surgical procedure is the main endpoint of our analysis. When comparing the surgical techniques, we did not find a significant difference between the 2 groups in regard to overall incidence rate of arrhythmias at any point of follow-up. In particular, the presence of EAR, intended as a direct consequence of an iatrogenic injury to the SA node, was not different between double- and single-patch repair groups. This is consistent with the work of Said et al (12), who did not observe a significant difference in the incidence number of SND and supraventricular arrhythmias among 124 patients treated by single or double patch technique or Warden procedure. On the contrary, other institutions reported different results in terms of incidence of postoperative arrhythmias between surgical groups, with a significantly higher frequency of non-sinus rhythm in patients who underwent double-patch repair. Stewart et al (13) showed a 55% incidence of supraventricular arrhythmias in the double-patch group, compared to significant lower incidence in single-patch and Warden groups (24% and 0%, respectively). Similarly, a recent paper by Jaschinski et al (14) displayed analogous features, where patients treated with the double-patch technique had a significantly higher incidence of non-sinus rhythm.
The reason behind the higher risk of iatrogenic SA node injury using the double-patch repair technique lies intuitively in the need for a more extensive superior cavo-atrial incision, which is a peculiar feature of this operation (7). In this surgical scenario, the possibility of damaging the SA node is certainly increased than in other procedures where the surgeon remains far away from this area, such as in the Warden and in the double-decker operations (10;15).
The SA node is the natural pacemaker of the heart. It is a complex sub-epicardial structure located in the antero-lateral aspect of the superior cavo-atrial junction. Its yellowish appearance on the external surface should allow the surgeon to identify and avoid it when carrying out the cavo-atrial incision. Nevertheless, anatomic variations of its extension and blood supply are common, thus explaining the high rate of postoperative SA node dysfunction.
In our analysis, we found a significantly higher incidence of SA node impairment in the pediatric population, and we acknowledge this may be of great importance. Perioperative incidence (early-onset) of EAR had a non-statistically significant increased trend in children compared to the adults, but when considering the long-term follow-up this difference becomes statistically significant, as EAR occurred overall in 32% of pediatric cases vs 8% of adult cases (p=0.02). In our opinion, this is likely to be the result of a much more common iatrogenic injury of the SA node in smaller patients, no matter which surgical technique is utilized. In young children indeed, the presence of small anatomical structures forces the surgeon to perform the cavo-atrial incision very close to the conduction system, increasing the risk of damaging the SA node. In adults instead, restoration of sinus rhythm over time occurred more frequently, perhaps because the larger dimension of the superior cavo-atrial junction and its distance from the SA node, makes the incision of cavo-atrial junction less likely to affect the conduction system. Conversely though, arrhythmias causing hemodynamic consequences were a significantly more common complication in adult patients, both in the early post-operative period and long-term. This is probably due, at least in part, to the long-standing volume overload and to the consequent distention of the right atrial fibres.
To our knowledge, this is the first study to analyze the different timing and pattern of post-operative arrhythmias in pediatric and adult patients undergoing PAPVC + sinus venosus ASD repair. We strongly believe that the significantly higher incidence of permanent SND with junctional or atrial ectopic escape among the pediatric patients could be related to the limited space between SA node area and cavo-atrial incision. In single-patch and especially in double-patch technique, a surgical incision of variable extension is performed across the cavo-atrial junction very close to the SA node (Figure 3). When the distance between the PV connection plan and the SA node is relatively wide, as in adult patients, the chance to interfere with the SA node activity is fairly minimal. On the other hand, when this distance is shorter, such as in pediatric patients, the probability of SA node dysfunction is increased. Therefore, the choice of surgical technique may play a crucial role to avoid the occurrence of iatrogenic SA node injuries causing certain arrhythmias, especially in the pediatric population. As initially mentioned, the Warden procedure is the most reproducible option to avoid surgical damage to the SA node, and there is nowadays increasing evidence of its superiority in terms of postoperative freedom from SND and EAR, compared to single- and double-patch procedures (9;10).
If results are confirmed by further larger studies, surgical procedures that completely avoid invasiveness and trauma at the level of superior cavo-atrial junction should probably be preferred in pediatric patients. Among the available techniques, although not free from other complications, the Warden procedure could be considered the safest and most reproducible (15). In our study population only one patient underwent the Warden procedure, and this was due exclusively to the surgeon’s preference. In view of our results and new insights, we believe that multicenter randomized prospective studies are needed to compare the arrhythmogenic effects of the Warden and double-patch techniques in children. In adult patients, in whom Warden procedure may present technical challenges in view of a lower mobility of the SVC, the double-patch technique will remain our preferred approach. Further studies are needed to specifically investigate the impact of EAR during growth in the pediatric population and to validate the protocol that will currently advocate at our institution.
The retrospective nature and the relatively small sample size are the main limitations of the present study. The bias may potentially be less if we take into account the consistency of a single center and the homogeneous surgical strategy, nevertheless larger and prospective studies are certainly warranted.
We also acknowledge that the follow-up was not complete for all patients, as 45 of them were lost at follow-up and were therefore excluded from the analysis. Nonetheless, their demographic and surgical characteristics were not dissimilar to those of patients who completed the follow-up.
The surgical management of PAPVC with sinus venosus ASD, requiring superior cavo-atrial incision, is associated with high incidence of postoperative SND (16). In our experience, this finding has been significantly higher among pediatric patients, probably due to the smaller cavo-atrial junction size and the subsequent close proximity of the SA node to the PV connection site and surgical incision, hence increasing the risk of iatrogenic damage. Surgical techniques which avoid manipulation of the superior cavo-atrial junction should therefore be preferred in pediatric patients.