Abstract
A 23-year-old woman presented with 200,409 heart beats/day due to an atrial tachycardia (AT) lasting one year and tachycardia-induced cardiomyopathy. None of the antiarrhythmic or rate control drugs terminated the AT or sufficiently reduced the heart rate during the AT. Thus, she underwent radiofrequency catheter ablation of the AT. Ultra-high-resolution mapping suggested that the AT originated from the epicardial left atrial appendage (LAA), and endocardial radiofrequency ablation failed to eliminate the AT, although acceleration and transient termination of the AT during ongoing ablation in the endocardial LAA were observed. After the ablation, ivabradine monotherapy achieved both an optimal heart rate control during the AT and termination of the AT. Some ATs refractory to conventional antiarrhythmic drug therapy can be treated by ivabradine and are called ivabradine sensitive-ATs (ISATs). Left atrial ISATs often originate from the vicinity of the LAA and have been reported to be treated by endocardial radiofrequency ablation. This case report describes that a subset of ISATs originating from the LAA may be associated with epicardial abnormal automaticity and refractory to conventional endocardial radiofrequency ablation. LEARNING OBJECTIVE: Some focal atrial tachycardias (ATs) refractory to conventional antiarrhythmic drug therapy are successfully treated by ivabradine and are called ivabradine sensitive-ATs (ISATs). ISATs originating from the left atrial appendage (LAA) have been reported to be eliminated by endocardial radiofrequency ablation, but a subset of LAA-ISATs may be associated with epicardial abnormal automaticity and may be refractory to endocardial radiofrequency ablation.