Arrhythmias and conduction disorders associated with atrial septal defects.

Atrial septal defects (ASDs) are the most common form of congenital heart disease. There are 4 embryologic types of ASDs, and rhythm considerations vary based on type. ASDs have left-to-right shunt and primarily right-sided volume overload. This leads to electrical remodeling that may predispose patients to atrial tachyarrhythmias and conduction disorders. Risk for arrhythmias is increased with late age of ASD repair, shunt size, other factors such as pulmonary hypertension and comorbid conditions. Arrhythmia incidence is decreased after ASD closure, but remains elevated compared to general population. Medical and procedural therapy for arrhythmias should consider type and timing of ASD repair. Conduction disorders are rare. Sinus node dysfunction may be seen with late age of repair and large shunt size. Sinus venosus ASD exhibits a higher rate of sinus node dysfunction, especially with older surgical techniques. Ostium primum ASD has higher risk of spontaneous or post-operative AV block, though this is rare with current surgical techniques. Risk of AV block with surgical repair or device closure of secundum ASD is rare. Familial ASDs and other forms of congenital heart disease may be seen with mutations in associated myocardial transcription factors NKX2.5, GATA4, TBX6, along with conduction disorders such as AV block.