Discussion

The optimal age for surgical correction of CAVC defect has been addressed in several studies, most of which showed that successful repair at an early age was associated with competent AV valves at the time of diagnosis, even in the presence of a cleft in the LAVV component. ^{Reference Yasui, Nakamura and Kado18,Reference Mavroudis, Weinstein, Turley and Ebert19} Patients repaired at older ages were found to be more likely presenting with an incompetent AV valve. ^{Reference Mavroudis, Weinstein, Turley and Ebert19,Reference Günther, Mazzitelli, Haehnel, Holper, Sebening and Meisner20} This may be due to chronically elevated QP/QS playing an important role in the onset of annular dilatation and secondary LAVV incompetence. ^{Reference Michielon, Stellin, Rizzoli and Casarotto9,Reference Mavroudis, Weinstein, Turley and Ebert19} Early correction has been proposed to reduce the incidence of LAVV regurgitation in the post-operative follow-up period. ^{Reference Suzuki, Bove and Devaney21,Reference Atz, Hawkins and Lu22} This appears to be the most important factor affecting post-operative morbidity and mortality. ^{Reference Stellin10} Avoiding irreversible pulmonary hypertension, which may develop before the age of 6 months particularly in the presence of Trisomy 21, is another reason to justify earlier repair. ^{Reference Stellin10,Reference Suzuki, Bove and Devaney21} Some studies advocate that the optimal timing for surgical intervention in patients with CAVC defect is when symptoms of congestive heart failure cannot be managed by medical therapy. ^{Reference Reddy, McElhinney and Brook23} Others believe that repair at the age of 4–6 months, before developing severe pulmonary hypertension, gives better results with no additional morbidities or mortality. ^{Reference Suzuki, Bove and Devaney21,Reference Atz, Hawkins and Lu22,Reference Singh, Warren, Reece, Ellman, Peeler and Kron24}

In our study, we found no statistical significant difference between early surgical repair of CAVC defect in the first 6 months versus later repair, both in regards to mortality and post-operative LAVVR. The only significant finding was in the ICU duration, which was longer in the younger age group. Stellin et al ^{Reference Stellin10} performed a study assessing surgical treatment of CAVC defects in children before 3 months of age, with findings demonstrating that repair of CAVC under 3 months of age is the ideal approach to this malformation with a lower mortality rate at operation compared to older patients. ^{Reference Stellin10,Reference Singh, Warren, Reece, Ellman, Peeler and Kron24} Logistic analysis showed that an operative age after 3 months is compared to an age before or equal to 3 months, an incremental risk factor for hospital mortality with an odds ratio of 4.8 (95% confidence limit 1–23.5) (p-value = 0.05). ^{Reference Stellin10} In the long term, freedom from reoperation for LAVV incompetence is higher when compared to children repaired at an older age. ^{Reference Stellin10}

Parikh et al ^{Reference Parikh, Shah, Myers, Kunselman and Clark25} found no differences between the early (<90 days) and late repair (>90 days) age groups at surgery for the outcomes of post-operative length of stay, heart block requiring pacemaker placement, rate of moderate or greater LAVVR, reoperation for LAVVR, and mortality. ^{Reference Parikh, Shah, Myers, Kunselman and Clark25}

Both modified single-patch and double-patch techniques can be used for the repair of CAVCD, with the former being superior in having shorter bypass time and cross-clamp time, making it more popular, ^{Reference Nicholson, Nunn and Sholler11,Reference Fong, Winlaw and Orr26} although some surgeons believe that it may have associations with a higher incidence of LVOT obstruction.

In our study, when compared to the double-patch techniques, patients with a modified single patch had significantly shorter cross-clamp time, bypass time, and duration of ICU stay. Surgeons’ preference in deciding which technique to use in the surgical repair is one important factor, some surgeons tend to use double-patch technique with large VSD component, others favour the use of modified single-patch technique in complete AVSD with large VSD (larger than 0.8 mm and up to 1.5 mm), both, however, were found to have comparable results and outcomes . ^{Reference Nicholson, Nunn and Sholler11,Reference Fong, Winlaw and Orr26}

Addition of posterior annuloplasty to the common AV valve repair was suggested to prevent late reappearance of LAVVR. ^{Reference Fong, Winlaw and Orr26} In this study, it showed a protective effect against moderate-to-severe LAVVR and short-term mortality 6 months post-operatively, when compared to the closure of cleft only. We believe that posterior annuloplasty maintains the valve competency and also restricts progressive dilatation of the LAVV, hence decreasing the need for reoperation. In a study performed by Myers et al, 219 patients were included to evaluate the impact of annuloplasty at CAVC repair on post-operative LAVV function. ^{Reference Myers, del Nido and Marx27} The cleft was closed completely in 192 patients (88%). Sixty-five patients had annuloplasty (39 commissural, 32 posterior). There were five early deaths (2.3%). At discharge, four patients (1.9%) had more than mild regurgitation and no patients had significant inflow gradients. During a follow-up of 2.7 ± 2.1 years, there were 6 late deaths (2.8%), and 16 patients (7.3%) required LAVV reoperation. Two of 65 patients (3.1%) with annuloplasty required reoperation, compared to 14 of 148 without annuloplasty (9.5%, p = 0.16). In propensity matched analysis, annuloplasty was significantly protective of ≥ moderate LAVVR (OR 0.19, p = 0.008) and non-significantly of reoperation (OR 0.28, p = 0.099). ^{Reference Myers, del Nido and Marx27}

There was a significant difference between Trisomy 21 patients and Non-Trisomy 21 patients regarding post-operative, early, and 6 months follow-up LAVVR. Additionally, there was a significantly higher incidence of common AVV dysplasia and malformation in Non-Trisomy 21 patients when compared to Trisomy 21 patients. Similar findings were presented in Al-Hay et al, where 32% Non-Trisomy 21 compared to 11% with Trisomy 21 were reoperated (p = 0.005). Of the patients reoperated, survival probability was significantly higher in patients with Trisomy 21 versus Non-Trisomy 21 patients. ^{Reference Al-Hay, MacNeill, Yacoub, Shore and Shinebourne28} The significant difference between post-operative LAVVR between the two groups may be due to the difference in AV valve dysplasia and malformations, which makes surgical repair of LAVV and maintenance of valve competency much more difficult, regardless of surgical technique used. In Al-Hay et al, a cardiac aberration identified as a major risk factor was the presence of a double-orifice AVV; patients with this cardiac abnormality had significantly lower survival rates. ^{Reference Al-Hay, MacNeill, Yacoub, Shore and Shinebourne28} Meanwhile, in a case report by Mahadevaiah, discussion followed a neonate with Trisomy 21 in conjunction with AVSD as well as hypertrophic cardiomyopathy and pulmonary vein stenosis. Whilst pulmonary vein stenosis is a rare subject of medical literature, it resulted in fatal levels of hypoxia following catheterisation. ^{Reference Mahadevaiah, Gupta and Ashwath29}

Formigari et al found there were no significant differences in survival between Trisomy 21 and Non-Trisomy 21 patients with overall mortality being 7.7%. ^{Reference Formigari, di Donato and Gargiulo30} Survival was 94% amongst patients with Trisomy 21 versus 86% of Non-Trisomy 21patients (p = 0.12). When comparing the incidence of reoperation due to post-operative LAVVR or LVOT obstruction, a higher prevalence of reoperation in CAVC was found in Non-Trisomy 21 patients (81.4 versus 94.6%, p = 0.04), due to the higher prevalence of anomalies of the mitral valve (4.9 versus 1.8%, p 0.03), as well as higher LVOT prevalence (7.3 versus 0%, p 0.01). ^{Reference Formigari, di Donato and Gargiulo30}

Kaza et al found some preoperative and intraoperative differences between the two groups but of no significance, and outcomes were found to be similar. ^{Reference Formigari, di Donato and Gargiulo30} Hospital courses were also similar with the exception of a number of in-hospital complications (higher in the Non-Trisomy 21 group). Mortality at 6 months was identical at 4%, but there was a trend towards more reoperations in the first 6 months in the Non-Trisomy 21 group (13 versus. 2%, p = 0.06). ^{Reference Kaza, Colan and Jaggers31} Moderate or severe LAVVR was more likely in the Non-Trisomy 21 group prior to AVSD surgery, however, the prevalence of LAVVR did not differ at 1 month and 6 months post-surgery. ^{Reference Kaza, Colan and Jaggers31}

We can conclude that Trisomy 21 is no longer a risk factor for adverse outcomes regarding post-operative LAVVR and mortality, so early intervention in the first 6 months in patients with Trisomy 21 is advocated to provide better results when compared to Non-Trisomy 21 patients, and gives comparable results compared to delaying surgery after 6 months.