Electrical instability in patients undergoing surgery for atrioventricular septal defect.

Postoperative 24-hour Holter monitoring was performed in 106 patients with atrioventricular septal defect in order to identify the incidence of atrial and ventricular arrhythmias. Of the patients, 72 had separate atrioventricular orifices, including 13 with a small ventricular component to the defect, and 34 patients had a common atrioventricular orifice. Two groups of abnormal patients were found. First, patients with good electrical stability characterized by isolated atrial (9 patients) and ventricular (25 patients) extrasystoles falling in classes I and II of Lown. Second, patients with marked electrical instability characterized in one patient by repetitive atrial extrasystoles, in another by atrial flutter, in 2 by polymorphic ventricular extrasystole and in 8 by couplets or triplets. Electrical instability in individual patients was then compared, by means of logistic regression analysis, with operative, surgical and postoperative variables. There was no incidence of sudden death in our series. After surgical repair, ventricular arrhythmias were more frequent than atrial arrhythmias (33% vs. 10%) and were unrelated to the type of atrioventricular septal defect. Cardiac electrical instability after operation was significantly related to larger operative body size, higher postoperative end diastolic diameter of the right ventricle, larger size of the ventricular septal defect, coexistence of postoperative right bundle branch block and left anterior hemiblock. Conversely, the risk of arrhythmias was reduced by more recent operative data and by greater shortening fraction of the left ventricle.