Iterative atrial tachycardia originating from the coronary sinus musculature

Coronary Sinus Atrial Tachycardia. A case of iterative atrial tachycardia l eading to dilated cardiomyopathy is reported. During electrophysiologic stu dy, the tachycardia showed a markedly irregular cycle length associated wit h changes in atrial activation breakthrough as demonstrated by coronary sin us (CS) recordings and frequently degenerated into self-terminating atrial fibrillation. Left atrial transseptal mapping demonstrated the earliest end ocardial atrial activation close to the posterolateral mitral annulus, but this was invariably later than that recorded within the CS, where low-energ y radiofrequency applications eliminated the tachycardia. No acute vessel d amage was observed at post-ablation CS angiography. In accordance with prev iously published experimental data, we hypothesized that the muscular sleev es surrounding the CS might be involved in the genesis of this tachycardia. During 6-month follow-up, the patient remained asymptomatic without tachyc ardia recurrences and with complete recovery of left ventricular function, confirming the reversible nature of the tachycardia-induced cardiomyopathy.