Morphometric Analysis of Unbalanced Common Atrioventricular Canal Using Two-dimensional Echocardiography

Objectives: This study was designed to define morphometric echocardiographic variables of unbalanced common atrioventricular canal (CAVC) that could aid in appropriate referral for surgical repair.

Background: Unbalanced CAVC has a high surgical mortality rate. This may be secondary to inappropriate referral of some patients for two-ventricle repair (closure of septal defects) instead of single-ventricle repair (Norwood palliation and Fontan operation).

Methods: The echocardiograms of 103 patients with CAVC were retrospectively reviewed. In the subcostal left anterior oblique view, the area of the atrioventricular (AV) valve aportioned over each ventricle was measured, and an AV valve index (AVVI) was calculated as left/right valve area. The ventricular cavity ratio between the two ventricles was estimated as left ventricular length times width divided by right ventricular length times width. These variables were correlated with surgical referral and outcome.

Results: Patients previously categorized as having balanced CAVC all had AVVI > 0.67 (n = 77). Of the patients with unbalanced CAVC (n = 26), 11 had ductal-dependent circulation and underwent Norwood palliation (AVVI 0.21 +/- 0.13, mean +/- SD), and 15 had two-ventricle repair (AVVI 0.51 +/- 0.12, p < 0.0001). Of these 15 patients, 9 have survived, with no difference in mean AVVI between survivors and nonsurvivors (0.52 +/- 0.11 versus 0.49 +/- 0.13, p = 0.72). For all 103 patients, AVVI correlated with ventricular cavity ratio. However, of the unbalanced CAVC group who underwent two-ventricle repair, three nonsurvivors had a discrepancy between AVVI and ventricular cavity ratio (low AVVI but normal ventricular size). A large ventricular septal defect was present in all six nonsurvivors but in only four of nine survivors (p < 0.05).

Conclusions: Echocardiographic morphometry is useful in defining unbalance in CAVC. If AVVI is < 0.67 in the presence of a large ventricular septal defect, a single-ventricle approach to repair should be considered.