Mapping and Ablation of an Atrial Tachycardia Determined to be Originating from the Interatrial Septal Region

Rishi Anand, MD, Jason Petusevsky, and Bhavya Suri, Holy Cross Hospital, Fort Lauderdale, Florida
Rishi Anand, MD, Jason Petusevsky, and Bhavya Suri, Holy Cross Hospital, Fort Lauderdale, Florida

Case Description

A 79-year-old woman presented with onset of severe narrow complex tachycardia with a heart rate of 180 beats per minute. She is known to have preserved left ventricular function with no prior myocardial infarction. She failed medical therapy with atrioventricular nodal blockers and therefore presented to the EP lab for catheter ablation. 

During the EP study, the patient had inducible supraventricular tachycardia (SVT) with atrial burst pacing (cycle length of 330 msec) with 1:1 atrioventricular conduction. Entrainment of the tachycardia via ventricular pacing confirmed a V-A-A-V response substantiating an atrial tachycardia (Figure 1). Activation mapping in the right atrium during tachycardia demonstrated the earliest site of activation to be originating from the interatrial septum close to the AV node-His bundle region. The ablation catheter was then positioned at the point of the earliest atrial activation within the right atrium and ablation was attempted without termination of the SVT. The decision was made to continue mapping of contiguous structures such as the aortic root/noncoronary cusp and if necessary, the left side of the interatrial septum. Aortic root arteriogram was performed in a left anterior oblique view to ascertain the fluoroscopic relation of the coronary arteries in relation to the arrhythmia focus.

After further activation mapping of the noncoronary cusp, the earliest atrial activation was determined to be 83 msec before the onset of the surface P-wave. (Figure 2) Minor repetitive fractionation could be seen on the ablation distal catheter consistently 83 msec before the onset of the surface P-wave, suggesting this was an ideal location to attempt ablation. No His bundle signals were seen on the ablation catheter. Ablation was performed at 15 Watts with a ThermoCool catheter (Biosense Webster, Inc., a Johnson & Johnson company), resulting in termination of the tachycardia in 8 seconds. (Figures 3 and 4)


Atrial tachycardia ablation has a reported success rate from 69–100%, with a low incidence of complications.1 Recurrence rates vary from 0–33%. Ablation of the interatrial septal region carries more risk because of its proximity to the electrical conduction system.2 When mapping atrial tachycardias determined to be arising from the interatrial septal region, especially those in close proximity to the AV node-His bundle, it is appropriate to bear in mind the close proximity of the aortic coronary cusps to the interatrial septum. If cautious ablation from within the right atrium is unsuccessful, one needs to consider mapping of the aortic root coronary cusps and/or the left side of the interatrial septum and right-sided pulmonary veins to further locate the origin of the atrial tachycardia emanating from close to the interatrial septum. 

Disclosures: The authors have no conflicts of interest to report regarding the content herein. 


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