Predicting recurrence after cardioversion
SEOUL, KOREA. Approximately 50% of afibbers undergoing electric cardioversion (CV) experience recurrence within the first month following the procedure. The extent of electrical and structural remodeling of the left atrium (LA) is known to affect the risk of recurrence. Now a team of Korean researchers report that several other factors influence whether a CV results in long-term normal sinus rhythm (NSR).

Their study involved 81 patients with an average age of 59 years (78% male) who had been taking an antiarrhythmic drug (AAD) for at least one month prior to the CV and who were on an optimal anticoagulation protocol. Sixteen percent of the study participants had heart failure and 26% had hypertension so, although not stated, the majority of the participants were lone afibbers (no underlying heart disease). The mean left ejection fraction (LEF) was 49%, the mean LA diameter was 45.5 mm, and 58% of the participants showed spontaneous echo contrasts (SECs) in the left atrium – despite supposedly optimal anticoagulation.

All patients underwent CV with an initial biphasic R-wave synchronized shock at 70 J increasing to 100, 150 or 200 J if the first shock failed to achieve NSR. If afib returned within 15 minutes, amiodarone was administered intravenously and the CV repeated. Patients still in afib after this were classified as having failed CV. Seven patients (8.6%) failed CV leaving 74 patients for follow-up at 1, 2, 4 and 8 weeks and then every 3 months. After an average 13-month follow-up, 65% were back in afib, while 35% remained in NSR. The median time to recurrence was 21 days. The following statistically significant differences were found between the group that experienced recurrence and the one that remained in NSR.
(1) stromal cell-derived factor
(2) pro-atrial natriuretic peptide
(3) ACE inhibitors or angiotensin II receptor blockers

CV failure was less common in patients on amiodarone (29% vs 65%) and high levels of transforming growth factor (TGF-beta) were associated with immediate CV failure. Recurrence of afib following a successful CV (after adjusting for confounding variables) was more common in patients older than 60 years, those with SEC, and those with low levels of SDF-1 alpha. Under-utilization of ACE inhibitors, ARBs, and spironolactone was associated with a greater risk of recurrence. Left atrial diameter and level of C-reactive protein were not associated with recurrence.

Kim, SK, et al. Clinical and serological predictors for the recurrence of atrial fibrillation after electrical cardioversion. Europace, Vol. 11, December 2009, pp. 1632-38

Editor's comment: This study clearly shows that remaining in sinus rhythm after a seemingly successful CV is the exception rather than the rule. It is unfortunate that the researchers did not measure potassium and magnesium levels prior to the procedure. It is likely that they would have been found to be low in light of the seemingly beneficial effect of potassium- and magnesium-sparing drugs (ACE inhibitors, ARBS, and spironolactone). In any case, it is important to ensure adequate potassium and magnesium stores prior to a CV and it may well be that taking one of the above-mentioned drugs prior to and after a CV may extend the time to recurrence.