Echocardiographic Evaluation of Common Atrioventricular Canal Defects: A Study of 206 Consecutive Patients

An accurate echocardiographic evaluation of common atrioventricular canal (CAVC) requires in-depth knowledge of the wide spectrum of morphological and physiological variations in this group of anomalies. In order to evaluate the incidence and morphological distribution of AV canal defects in a large series of patients and to define a systematic approach to the echocardiographic examination, we reviewed the echocardiograms of 206 consecutive patients with CAVC studied at Texas Children's Hospital over a 32-month period. The complete form of CAVC was most common (68.4%) and presented at an earlier age (mean +/- SD: 1.6 +/- 2.4 months). A partial AV canal (ostium primum atrial septal defect [ASD]) was found in 42 patients (20.4%) and their age at presentation was higher (9.2 +/- 10 months). Twenty-three patients (11.2%) had a transitional AV canal. Down syndrome was diagnosed in 34% of patients, the majority of whom (79%) had a complete CAVC. Associated malformations were found in 46% of patients: anomalies of the conotruncus were most frequent (18%), followed by secundum ASD (14.1%), anomalous pulmonary venous connection (11.2%), and heterotaxy syndrome (11.2%). Subaortic obstruction and mitral stenosis were less common. The AV canal was unbalanced in 14.1% of patients, with the right ventricular dominant form being more common than the left ventricular dominant form (10.7% and 3.4%, respectively). Based on our experience, we developed a systematic, segment-by-segment approach to the echocardiographic examination in infants with CAVC. Together with detailed anatomical information, Doppler evaluation provides crucial hemodynamic information that allows planning of surgical repair. (ECHOCARDIOGRAPHY, Volume 13, July 1996)