Electrocardiographic and Angiographic Features of Common Atrium

¹ Mayo Clinic and Mayo Foundation, Rochester, Minn

Electrocardiograms and large film biplane angiocardiograms were reviewed in 14 cases of anatomically proved common atrium. All were associated with persistent atrioventricular canal. Electrocardiograms (available in 12 cases) revealed frontal plane QRS loops consistent with persistent atrioventricular canal. Horizontally or superiorly oriented abnormal P vectors were observed in 7 of 12 (58 percent) cases, only one of which was associated with persistent left superior vena cava. None of the cases with a persistent left superior vena cava had a coronary sinus. Abnormal atrioventricular conduction was encountered in two thirds of the cases. In all eight cases in which left ventriculograms were reviewed, typical goose-neck deformity diagnostic of persistent atrioventricular canal was observed. In the five cases in which atrial structure was studied either after the injection of contrast material into the right ventricle or directly into the atrium, a single large globular atrial structure was demonstrated. Although clinical examination and hemodynamic study often cannot distinguish common atrium from the more frequently encountered secundum and primum types of atrial septal defects with large intra-atrial communication, diagnosis of common atrium can be made if the following findings are present: an abnormal frontal plane P axis in conjunction with a frontal QRS loop consistent with persistent atrioventricular canal in the electrocardiograms, and the demonstration of a single atrial structure by large film biplane angiocardiograms after rapid injection of contrast material into the right ventricle, into the main pulmonary artery, or directly into the atrium.