Discussion

The objective of this study was to determine the association between timing of repair of complete atrioventricular septal defect and both resource utilisation and clinical outcomes in the first year of life. In contrast to our hypothesis, we found that earlier repair was not associated with differences in the most important measures of resource consumption. As we anticipated, age at surgery was not associated with meaningful differences in clinical outcomes.

Our findings need to be interpreted in the context of prior studies on timing of surgery in this patient population. Atz et al. previously evaluated factors associated with suboptimal outcomes in 120 patients who underwent complete atrioventricular septal defect repair at multiple medical centres. These investigators found that age at surgery less than 2.7 months was associated with increased resource utilisation and adverse outcomes. ^{Reference Atz, Hawkins and Lu11} Similarly, several studies have found that age less than 2.5 – 3.0 months and weight less than 4 kg at the time of surgery are risk factors for increased mortality in this population, which was thought in part to be due to the presence of more fragile left atrioventricular valve tissue in these young infants. ^{Reference St Louis, Jodhka and Jacobs2,Reference Schleiger, Miera and Peters10,Reference Burstein, Gray and Griffis12} In contrast, other single-centre studies have found that operation at less than 3 months of age was not associated with increased mortality. ^{Reference Reddy, McElhinney, Brook, Parry and Hanley3,Reference Kogon, Butler, McConnell, Leong, Kirshbom and Kanter7,Reference Parikh, Shah, Myers, Kunselman and Clark8,Reference Stellin, Vida and Milanesi13} It is possible that we did not find significant differences in resource utilisation among age groups in our study because we only included uncomplicated cases, and the overall outcomes at our centre were quite good (i.e., no mortality and rare cardiac reinterventions in the first year of life for the patients in this study). It should be noted that our study only included one patient who underwent complete atrioventricular septal defect repair at less than 2.7 months of age, and thus, our findings cannot be used to inform decision making for complete atrioventricular septal defect repair in the first 3 months of life. Atz et al. also noted increased length of hospital stay associated with patients with non-cardiac anomalies, which were excluded from our study. ^{Reference Atz, Hawkins and Lu11}

The precise reasons for timing of surgery in the study patients are not easily gleaned from the medical record. Nuances such as judgement of the cardiologist, parental sense of urgency to have the heart “fixed,” and surgical scheduling issues are unknown. Another potential confounder is the relationship between birth weight and perceived optimal weight at the time of surgery. Other things being equal, many cardiac surgeons prefer that patients undergoing elective complete atrioventricular septal defect repair weigh approximately 5 kg at the time of the operation. In our study subjects, there was an inverse relationship between birth weight and age at surgery. It is possible that clinicians were delaying surgery for patients who ultimately ended up in the older age tertiles to allow for more weight gain.

We speculated that patients undergoing surgery at an older age would have more pre-operative problems with failure to thrive. However, the weight-for-age z-scores at surgery and at one year of age did not differ significantly among the three groups. We also anticipated that the patients that underwent surgery at a later age would have a higher resource utilisation due to more pre-operative testing, hospitalisations for intercurrent illnesses, and failure to thrive. However, pre-operative variables such as unplanned hospitalisations, medication use, and nasogastric or gastrostomy tube feeding pre-operatively were all found not to be significantly different across the age groups.

With regard to early post-operative outcomes, fewer ICU days were needed after surgery in the oldest age tertile when compared to the youngest tertile, but days of mechanical ventilation and hospitalisation were similar. Post-operative ICU days are known to be an imperfect outcome given that they can be influenced by a number of non-patient factors, such as availability of beds on the stepdown unit and nursing staffing. That being said, it is possible that critical care therapies aside from mechanical ventilation were weaned quicker in the older patients and/or clinicians felt more comfortable transferring them out of the ICU earlier. There were no significant differences in post-operative complications or feeding route at discharge. These findings are generally consistent with the previous studies that concluded that surgical intervention in this population can be done safely and effectively at a relatively early age, albeit with some increased length of ICU and hospital stay. ^{Reference Levenbrown, Bhat, Hossain, Derby and Pizarro6,Reference Kogon, Butler, McConnell, Leong, Kirshbom and Kanter7,Reference Atz, Hawkins and Lu11,Reference Azzab, Samy and Singab14–Reference Janai, Bellinghausen and Turton16} The lack of important differences in clinical outcomes and resource utilisation outcomes noted in this study was likely influenced by judgement utilised by clinicians practising in the Children’s Heart Program of South Carolina. For both pre-operative and post-operative variables, we speculate that patients who were not doing well with medical management were likely referred for surgery sooner, ultimately leading to equivalent outcomes among the age groups.

This study has several limitations. As with all retrospective studies, unmeasured confounding may have influenced outcomes. A more rigorous study design, such as a randomised trial in which eligible patients are assigned an age window for surgery shortly after birth, would certainly provide stronger evidence but is likely not feasible. As all study patients underwent surgery at one centre and were followed in a well-established statewide paediatric cardiology network, the findings may not be generalisable to other paediatric cardiac surgical programmes. The relatively small sample size may have limited our ability to detect differences in certain outcomes. A formal cost analysis was not performed but given the lack of differences in clinical measures of resource utilisation, would likely not add value to the study. Although emergency room visits or hospital days that occurred outside of the three study centres were not captured, given the lack of other tertiary paediatric hospitals in the state of South Carolina, any significant illnesses would have almost certainly resulted in transfer to one of the children’s hospitals for which we had access to medical records. Several potential variables of interest, such as discharge and follow-up echocardiogram findings, were not able to be assessed due to the fact that many of the subjects received perioperative care during the paper medical record era, and those charts are difficult to access.

We conclude that for uncomplicated balanced complete atrioventricular septal defect repair during infancy, age at surgery was not associated with important differences in clinical outcomes or resource utilisation in the first year of life. These findings may have been influenced by the judgement of clinicians who determined the timing of surgery for individual patients. The data suggest that in general, infants with uncomplicated balanced complete atrioventricular septal defects may safely undergo surgical repair at 3 to 4 months of age with a neutral effect on most important measures of resource consumption in the first year of life.