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(Circulation. 1997;96:3477-3483.)
© 1997 American Heart Association, Inc.

Articles

Progressive Anterior Ablation in the Coronary Sinus Region

Evidence to Support the Presence of a `Slow Pathway' Input in Normal Patients?

Andrew D. Krahn, MD; George J. Klein, MD; Raymond Yee, MD; Magdy N. Basta, MD; ; John K. Lee, MD

From the Division of Cardiology, University of Western Ontario, London, Ontario, Canada.

Correspondence to Andrew Krahn, London Health Sciences Center, University Campus, 339 Windermere Rd, London, Ontario, Canada N6A 5A5. E-mail akrahn{at}julian.uwo.ca

Background AV node modification is an emerging approach to rate control in patients with medically refractory atrial fibrillation. The mechanism of benefit of this procedure is not completely understood.

Methods and Results Twenty-two patients (age, 65±11 years; 16 women) with medically refractory paroxysmal atrial fibrillation referred for complete AV node ablation underwent serial ablations beginning at the level of the coronary sinus os progressing in a superior and anterior direction toward the His bundle. Serial atrial extrastimulus testing was performed to determine the effect of the progressive posteroseptal ablation in the region of the coronary sinus on the AV node antegrade refractory curve. Two of 22 patients had antegrade dual AV node pathways before ablation. Three patterns of response to serial ablation were noted. In 10 patients (45%), loss of the terminal portion of the AV node antegrade refractory curve occurred without evidence of fast pathway injury. In 7 patients (32%) the curve was shifted upward and to the left, consistent with nonspecific AV node damage. In 5 patients (23%), no effect could be attained before induction of complete AV block at superior and anterior ablation sites. Clinical variables and site of ablation did not predict response to serial ablations.

Conclusions These data suggest that the mechanism of benefit of AV node modification in this population may be through elimination of "slow pathway" tissue in half of patients and nonspecific injury in the remainder. Modification without complete AV block may not be possible in a minority of patients, as the response to progressive ablation appears to be "all or none" conduction.

Key Words: atrioventricular node • ablation • pathways • conduction

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