BORDEAUX, FRANCE. As more complex forms of atrial fibrillation (AF) are tackled with catheter ablation the incidence of post-procedure atrial tachycardia (AT) is increasing. The incidence of AT following AF ablation is now estimated to be between 5 and 50% depending on the duration of episodes and the type of mapping and lesion sets employed during the initial AF ablation. The AT is often more symptomatic than the afib it replaced, but in 1/3 to 1/2 of cases resolve on their own within a few weeks following the ablation. Unfortunately, AT tends to be resistant to normal antiarrhythmic therapy in which case a follow-up ablation specifically targeting the AT may be required.

Professor Michel Haissaguerre and colleagues at Hopital Cardiologique du Haut-Leveque have just published a two-part report on the mapping and ablation of AT following AF ablations. They now consider this AT a natural progression on the road from afib to normal sinus rhythm and make the following somewhat surprising statement:

Conversion of AF to one or more intermediate ATs is an important step in the maintenance of lasting sinus rhythm. Recurrence of AF is rarely seen after this conversion occurs, while it is the most common recurrent atrial arrhythmia when it does not.

In other words, experiencing atrial tachycardia after an AF ablation is a good rather than a bad sign.

AT can be macroentrant or focal in origin and is often associated with gaps in the lesions made during the AF ablation. The origin of the AT is established by careful electrophysiological mapping. The first step involves checking that the isolation of the pulmonary veins is complete and, if it is not, filling in the gaps with fresh lesion lines. The second step involves the assessment of cycle length variability to see if the AT is of focal origin, while the third step involves checking for macroentrant circuits, particularly around the mitral valve and in the roof of the left atrium.

A recent study carried out by the Bordeaux group found that 46% of AT was macroentrant, while the remaining 54% was focal in origin (including localized reentry at the pulmonary vein junctions). The average mapping time to determine the origin of the AT was 10 minutes and 97% of all ATs were successfully mapped.

Veenhuyzen, GD, et al. Atrial tachycardias encountered during and after catheter ablation for atrial fibrillation: Part I: Classification, incidence, management. PACE, Vol. 32, March 2009, pp. 393-98
Knecht, S, et al. Atrial tachycardia encountered in the context of catheter ablation for atrial fibrillation: Part II: Mapping and ablation. PACE, April 2009, pp. 528-38

Editor's comment: The two articles by the Bordeaux group are most interesting, but highly technical and one has to once again marvel at the knowledge, skill and expertise that goes into bringing an afibber into consistent normal sinus rhythm through catheter ablation. One important take-home message is that "fixing" an atrial tachycardia occurring after a catheter ablation for afib requires careful and highly sophisticated electrophysiological mapping. Thus, selecting an EP using the electrophysiological approach (Haissaguerre and Natale protocols) rather than the electroanatomical approach (Pappone protocol) would probably be preferred.