To determine the prevalence of pacemaker and conduction disturbances in patients with atrial septal defects.

All patients with an atrial septal defect born before 1994 were identified in the Danish National Patient Registry, and 297 patients were analysed for atrioventricular block, bradycardia, right bundle branch block, left anterior fascicular block, left posterior fascicular block, pacemaker, and mortality. Our results were compared with pre-existing data from a healthy background population. Further, outcomes were compared between patients with open atrial septal defects and atrial septal defects closed by surgery or transcatheter.

Most frequent findings were incomplete right bundle branch block (40.1%), left anterior fascicular block (3.7%), atrioventricular block (3.7%), and pacemaker (3.7%). Average age at pacemaker implantation was 32 years. Patients with defects closed surgically or by transcatheter had an increased prevalence of atrioventricular block (p < 0.01), incomplete right bundle branch block (p < 0.01), and left anterior fascicular block (p = 0.02) when compared to patients with unclosed atrial septal defects. At age above 25 years, there was a considerably higher prevalence of atrioventricular block (9.4% versus 0.1%) and complete right bundle branch block (1.9% versus 0.4%) when compared to the background cohorts.

Patients with atrial septal defects have a considerably higher prevalence of conduction abnormalities when compared to the background population. Patients with surgically or transcatheter closed atrial septal defects demonstrated a higher demand for pacemaker and a higher prevalence of atrioventricular block, incomplete right bundle branch block, and left anterior fascicular block when compared to patients with unclosed atrial septal defects.