Left atrial scarring predicts ablation failure
CLEVELAND, OHIO. Both electrophysiological and anatomical mapping has shown that a significant proportion of afibbers have significant scarring in the left atrium. Researchers at the Cleveland Clinic now report that such scarring is a strong predictor of failure of the pulmonary vein antrum isolation (PVAI) procedure for the elimination of AF. Their study involved 700 patients who underwent a PVAI during the period January 2002 to August 2003. The average age of the patients was 53 years and a little over half had lone AF (no structural heart disease). All underwent a standard PVAI guided by intracardiac echocardiography (ICE). Prior to creating the ablation lesions, the electrical potentials of the left atrium wall were carefully mapped using a multipolar Lasso catheter (later checked by the use of a NaviStar (CARTO) catheter).

Areas with no electrical activity were classified as scarred tissue and patients exhibiting 3 or more such areas were classified as having left atrial scarring (LAS). On average, scar tissue covered about 21% of the total left atrium surface area. The 42 patients (6%) with LAS had, on average, a larger left atrium diameter, a lower left ventricular ejection fraction, and a much higher level of C-reactive protein (CRP) – 5.93 mg/L vs 0.31 mg/L in the non-LAS group. NOTE: A CRP level of 0.31 mg/L is at the lower end of the normal range thus indicating that the majority of afibbers in the non-LAS group (94% of total) did not have an elevated CRP level. There was also a trend for LAS patients to be less likely to have paroxysmal afib (26% vs 40% in the non-LAS group), but this trend was not statistically significant. Mean age, AF duration, and the incidence of structural heart disease were no different in the two groups.

All patients were prescribed an antiarrhythmic (dofetilide, flecainide, propafenone or sotalol) for a 2-month period (blanking period) after the completion of the PVAI and were then followed for an average of 16 months. The complete success rate (no afib, no antiarrhythmics) was 81% in the non-LAS group, but only 43% in the LAS group. Of the patients with afib recurrence, 17 of 24 in the LAS group and 117 of 128 in the non-LAS group underwent a second procedure. Complete success rate after the repeat procedure was 52% in LAS patients and 90% in non-LAS patients.

The researchers conclude that the presence of LAS is a strong predictor of PVAI failure with patients experiencing LAS having a 3.4 times greater risk of failure than non-LAS patients. They suggest that for those with LAS combining ablation with long-term drug therapy may be the most effective approach. It is also possible that more extensive ablation of the left atrial wall itself may prove helpful.

Verma, A, et al. Pre-existent left atrial scarring in patients undergoing pulmonary vein antrum isolation: an independent predictor of procedural failure. Journal of the American College of Cardiology, Vol. 45, No. 2, January 18, 2005, pp. 285-92

Editor's comment: Left atrial scarring, unfortunately, can only be determined by an electrophysiologic study, so it is not possible to say whether a patient is a good candidate for pulmonary vein ablation before the procedure is actually underway. None of the study participants had undergone a previous catheter ablation, so from this study it is not possible to conclude whether scar tissue originating from previous ablation(s) may also reduce the chance of success.