[Arrhythmias following closure of atrial septal defects. Apropos of 300 cases].

In a series of 300 cases whose atrial septal defects were closed (268 with ostium secundum, 27 with ostium primum, and 5 cases with both), arrhythmias were found in 60%. These were usually slow supraventricular arrhythmias caused by substitution (51%), and less commonly rapid supraventricular arrhythmias (27%), extra-systoles (16%), disorders of atrio-ventricular conduction of second and third degree and disorders of the auricle (6%). Conduction disorders were significantly more common (p less than 0.001) after closure of ostium primum (37%) than after closure of an ostium secundum (4.5%). Arrhythmias are most common during the first week (56%), and are usually of the slow type, and during the three succeeding weeks are markedly less frequent (31%) with a higher proportion (p less than 0.001) of the rapid type. No one anatomical type of ASD was complicated with arrhythmia more than the others. The slow type of arrhythmias occurred in the high ASDs, and the fast type especially amongst elderly patients. Longterm follow-up showed arrhythmias in 28% of patients with an ostium secundum defect. The factors influencing arrhythmias were age, cardiac enlargement, and the mean pulmonary arterial pressure. Arrhythmias were just as common in cases with a small shunt.