Transitional atrioventricular septal defect: diagnostic variability and its clinical significance

Discrepancies between preoperative echocardiographic diagnosis and intraoperative surgical findings for incomplete atrioventricular septal defects are frequently encountered. We assess the frequency of diagnostic discordance and its impact, focusing on subtype-specific predictors of the postoperative course.

We reviewed 172 patients post repair of incomplete atrioventricular septal defects at a single institution between November 2000-February 2025, including transitional atrioventricular septal defects (n = 74), partial atrioventricular septal defects (n = 71), and primum atrial septal defect with isolated left atrioventricular valve cleft (n = 27). Preoperative echocardiographic diagnoses were compared with intraoperative surgical diagnoses to determine diagnostic discordance and assess impact.

Baseline characteristics were similar across subtypes. Transitional atrioventricular septal defects were associated with a higher prevalence of syndromic diagnoses (52.7% versus 33.8% versus 22.2%, p = 0.008) and greater preoperative ventricular dilation (LVIDd Z-score -0.88 versus -1.70 versus -1.70, p = 0.031). Diagnostic discordance occurred most frequently in partial atrioventricular septal defects (74.6%), followed by primum atrial septal defect with isolated left atrioventricular valve cleft (37.0%) and transitional atrioventricular septal defects (13.5%) (p < 0.001). Transitional atrioventricular septal defect repairs were associated with longer cardiopulmonary bypass and cross-clamp times, prolonged ventilation, and longer hospital stays (all p < 0.05). Residual shunt was more frequent in transitional atrioventricular septal defects early postoperatively and at the last follow-up (p < 0.001). One death was observed in the partial atrioventricular septal defects group, reintervention rates were similar across subtypes (p = 0.643), and follow-up duration differed modestly between groups (p = 0.047).

The high rate of diagnostic discordance reflects inherent challenges in preoperative classification and suggests that a simplified, clinically oriented nomenclature may improve communication, surgical planning, and outcome prediction.