Pathophysiology, clinical course, and management of congenital complete atrioventricular block

The incidence of congenital atrioventricular (AV) block is between 1 in 15,000 and 1 in 20,000 births. It may occur in isolation or as a consequence of anomalous development of the conduction tissue in the context of a cardiac malformation. In this review, we use the term congenital AV bock to describe complete heart block when it is diagnosed in utero or at birth. The pathophysiological process is believed to be due to immune-mediated injury of the conduction system, which occurs as a result of transplacental passage of maternal anti-SSA/Ro-SSB/La antibodies. Many mothers are asymptomatic carriers, and less than one-third have a preexisting diagnosis of a rheumatological disorder. The AV block that develops months or years after birth probably occurs as a result of a different disease process that is poorly understood. The diagnosis of congenital AV block is usually confirmed by fetal echocardiography before birth and by electrocardiography after birth. The implantation of a pacemaker is recommended for symptomatic patients and for asymptomatic patients presenting with profound bradycardia, left ventricular dysfunction, a wide QRS interval, or a prolonged QT interval. It is now recognized that a subset of paced patients develop dilated cardiomyopathy and heart failure, and therefore regular follow-up is important. They are also at high risk of developing complications related to the presence of intracardiac material as a result of prolonged exposure to pacing materials. Future areas of research to minimize these risks include assessing the impact of alternative stimulation sites and the development of new cardiac stimulation techniques.