Discussion

Mortality following repair of partial or intermediate atrioventricular canal defect has been reported to be between 1% and 5%. ^{Reference Sojak, Kooij and Yazdanbakhsh2,Reference Mery, Zea-Vera and Chacon-Portillo5–Reference Buratto, McCrossan and Galati11} In this study, the in-hospital mortality rate was 5.2%, and the late mortality rate was 1.1%. For these patients, the literature conflicts regarding the correlation between age at the time of operation and mortality and reoperation. Buratto et al. found higher age at partial atrioventricular canal defect repair as a predictor of better long-term survival in their study of 249 partial atrioventricular canal defect patients with a median age of 2.9 (interquartile range: 1.4–5.1) years. ^{Reference Buratto, McCrossan and Galati11} Mery et al. supported these findings in their extensive series of 265 partial and intermediate atrioventricular canal defect patients and showed that infants were at a higher risk of reoperation. ^{Reference Mery, Zea-Vera and Chacon-Portillo5} On the other hand, Sfyridis et al. observed improved survival in intermediate atrioventricular canal defect patients with an operative age lower than 3 months and partial atrioventricular canal defect patients with an operative age under 2 years. ^{Reference Sfyridis, Sojak and Hazekamp12} In the current study, mortality was higher in partial or intermediate atrioventricular canal defect patients younger than 2.6 years.

Perioperative reoperation was an independent risk factor for in-hospital mortality. Both patients who were reoperated on in the perioperative period were reoperated on for left atrioventricular valve regurgitation. According to univariable analyses, although post-operative left atrioventricular valve insufficiency affects mortality, this was not demonstrated in multivariable analyses. Therefore, we attribute perioperative reoperation as being associated with the poor condition of the patients before reoperation and to the effects of cardiopulmonary bypass performed immediately after the index procedure. Interestingly, a need for right atrioventricular valve cleft closure or valvuloplasty was found to affect the in-hospital mortality rate. Since post-operative right atrioventricular valve insufficiency is not an in-hospital mortality risk factor, we cannot comment on this finding further.

After partial or intermediate atrioventricular canal defect primary repair in large series, the reoperation rate varies between 11.4% and 21%. ^{Reference Pontailler, Kalfa and Garcia4–Reference Welke, Morris and King6,Reference Buratto, McCrossan and Galati11} In these series, the follow-up period ranged from 60 months to 25 years. In this series, the reoperation rate was 10.3%. The fact that this rate is lower in this study may be due to the shorter follow-up period of 32 months compared to other clinical series. Previous studies have shown that left atrioventricular valve regurgitation is the most common cause of overall reoperations. ^{Reference Sojak, Kooij and Yazdanbakhsh2,Reference Mery, Zea-Vera and Chacon-Portillo5,Reference Sfyridis, Sojak and Hazekamp12} In our study group, left atrioventricular valve regurgitation was the most frequent indication for reoperation (seven of 10 [70%] patients). It is known that post-operative grade II or higher left atrioventricular valve regurgitation is associated with an increased reoperation rate for left atrioventricular valve regurgitation. ^{Reference Buratto, McCrossan and Galati11} The results of this study support this finding. Post-operative grade II or higher left atrioventricular valve regurgitation was also found to be a risk factor for overall reoperations. The rate of preoperative, post-operative, and follow-up grade II or higher left atrioventricular valve regurgitation was 31.9%, 16.3%, and 19.3%, respectively. Cleft or leaflet dehiscence is the primary mechanism for regurgitation, but annulus enlargement and chordae elongation are the other causes of insufficiency. ^{Reference Murashita, Kubota and Oba13} In this study, among eight out of nine reoperation patients, it was observed that cleft sutures were opened or the leaflet was separated from the annulus. The thin leaflet tissue was frequently torn at the sewing line of the cleft or the thinner point of the leaflet due to excessive tension. For decreasing the tension on the suture line, a cleft repair can be performed using pericardium-supported sutures, or a leaflet can be expanded by placing an autologous pericardium patch between the cleft edges. Although its effect on the reoperation rates was not statistically significant, adding an annuloplasty to the left atrioventricular valve cleft repair can reduce the tension on the cleft sutures by preventing dilation of the annulus and tearing of the sutures. In this study, seven (8.6%) of 81 patients who did not receive left atrioventricular valve annuloplasty underwent reoperation for left atrioventricular valve regurgitation. Among 16 patients who had left atrioventricular valve annuloplasty, one (6.2%) patient underwent perioperative reoperation. None of the 15 left atrioventricular valve annuloplasty patients required reoperation for left atrioventricular valve regurgitation.

The second most common reason for reoperation after atrioventricular canal defect surgery is left ventricular outflow tract obstruction. ^{Reference Chowdhury, Airan and Malhotra7,Reference VanArsdell, Williams and Boutin14} Mery et al., in their series of 265 partial and intermediate atrioventricular canal defect patients, reported a 7% left ventricular outflow tract reoperation rate at 10 years of follow-up. ^{Reference Mery, Zea-Vera and Chacon-Portillo5} Similarly, Buratto et al. reported a 6% reoperation rate due to left ventricular outflow tract stenosis at 15.1 ± 9.8 years of follow-up. ^{Reference Buratto, McCrossan and Galati11} In our study, only one patient had subaortic stenosis at the latest follow-up echocardiography. In this study, we attribute lower left ventricular outflow tract reoperation rates to shorter follow-up times than in the series mentioned above, and we think that left ventricular outflow tract-related intervention will be required in the subsequent follow-up period. The incidence of residual atrial septal defect or ventricular septal defect has been reported as 0% to 11%. ^{Reference Pontailler, Kalfa and Garcia4,Reference Chowdhury, Airan and Malhotra7,Reference Minich, Atz and Colan8,Reference Buratto, McCrossan and Galati11,Reference Stulak, Burkhart and Dearani15} In this study, six patients had residual atrial septal defect of different sizes, while four patients had restrictive ventricular septal defect. Residual atrial septal defect can be seen due to the separation of the patch due to superficial bites in order not to cause a block in the conduction system. Residual ventricular septal defect is caused by tiny leaks passing through the stitches placed in thickened tissues formed due to longstanding turbulence secondary to restrictive flow. Small residual ventricular septal defects can be followed up due to the possibility of spontaneous closure. ^{Reference Dodge-Khatami, Knirsch and Tomaske16} In our study, one patient had reoperation due to the need for cleft repair and residual atrial septal defect closure, while the remaining patients with residual intracardiac shunts were followed up. In this study, a residual atrial septal defect or ventricular septal defect, another risk factor for overall reoperations, might show its effect as increased volume or pressure load further increasing atrioventricular valve regurgitation and worsening the clinical picture. If there is no accompanying valve failure, an insignificant atrial septal defect or ventricular septal defect might not directly affect the reoperation rate. The fact that none of the patients in this series were reoperated on for isolated atrial septal defect or ventricular septal defect supports this idea. There are different findings on the effect of timing of surgery on reoperation rates. Delvin et al. classified and examined 86 patients in their series as quartiles, that is, 0–0.75 years of age, 0.75–1.5 years of age, 1.5–3.75 years of age, and over 3.75 years of age. In their series, patients underwent partial atrioventricular canal defect repair at a median age of 1.5 years. The authors recommended surgery before two years of age, as there was no significant difference between age groups in terms of reoperation, late atrioventricular valve regurgitation, or stenosis. ^{Reference Devlin, Backer and Eltayeb17} In the series from Minich et al., significant left atrioventricular valve regurgitation occurred 6 months after the surgery in eight of nine children repaired between ages 4 and 7 years compared with 11 of 50 repaired at less than 4 years or later than 7 years of age. ^{Reference Minich, Atz and Colan8} Regarding the extensive series from Texas Children’s Hospital and Mayo Clinic, a repair later in life might be reasonable if the patient is stable on medical therapy. ^{Reference Mery, Zea-Vera and Chacon-Portillo5,Reference El-Najdawi, Driscoll and Puga18} Although age was not found to be a risk factor for reoperation in our study, our clinical practice is to perform the surgery later in life to benefit from leaflet tissue that is more resistant to tension so long the patient uses low-dose medication. The retrospective and single institutional nature were the main limitations of the study. Since echocardiographic images of many patients were not available, evaluations were made based on reports. Valve pathologies could not be examined in detail since some surgery notes did not specify the valve structures.