The development of atrial reentry depends on the presence of a circuit with unidirectional block and a zone of slow conduction. Structural heart disease can be detected in about 50 percent of patients with intra-atrial reentry. This tachycardia is particularly common in patients who have undergone surgery for congenital heart disease.
Reentry occurs around obvious structural barriers, such as suture lines.
In patients without obvious cardiac disease, more subtle changes, such as scarring and fibrosis, provide substrates for reentry. Automatic Atrial Tachycardia Automatic atrial tachycardia arises from focal sources having abnormal automaticity and does not require the presence of a reentrant circuit. Young patients with automatic atrial tachycardia may have structurally normal hearts. In older patients, structural and metabolic derangements may contribute to the development of automatic atrial tachycardias. Differentiation between automatic atrial tachycardia and intra-atrial reentry tachycardia may be difficult.