Predicting cardioversion success
TURIN, ITALY. Electrical cardioversion (ECV) is considered first-line treatment for persistent atrial fibrillation (AF) defined as paroxysmal (intermittent) AF which does not self-terminate, or is sustained beyond 7 days. Although the acute (immediate) success rate of cardioversion is acceptable, only about 50% or less of patients undergoing ECV remain in normal sinus rhythm (NSR) a year following their cardioversion.

A group of researchers from the University of Turin recently released the results of a study aimed at determining the main factors influencing cardioversion outcome. Between January 2005 and December 2009 a total of 521 persistent afibbers were enrolled in the study. About half the participants had structural heart disease, 67% had hypertension, and 11% had suffered a previous stroke or TIA. Only 5% were classified as having idiopathic (lone) AF.

The study participants were divided into 4 groups according to the length of time they had spent in AF prior to undergoing ECV. Group A consisted of 141 patients who had been in AF for 2 months or less, group B comprised 176 patients who had been in AF for more than 2 months but no more than 4 months, group C comprised 89 patients who had been in AF for more than 4 months but no more than 6 months, while group D consisted of 115 patients who had been in AF for more than 6 months. Eighty-five percent of participants were on antiarrhythmic drugs (53% on amiodarone and 28% on flecainide or propafenone) prior to ECV and continued on these drugs after their cardioversion. They were also anticoagulated for 4 weeks before and 12 weeks after ECV.

All participants underwent direct-current biphasic shock with an initial energy of 200 Joule. Acute and long-term success rates for the 4 groups are shown below.

The researchers conclude that waiting more than 6 months for cardioversion is associated with a significantly reduced chance of remaining in sinus rhythm over the long term. They also observed that having an enlarged left atrium, as well as having had a prevision cardioversion, markedly reduced the chance of a successful long-term outcome. Thus, the combination of AF duration more than 6 months, an enlarged left atrium, and a previous ECV reduced 5-year success rate to 13%.

During the first 30 days after the ECV, one 79-year-old woman (CHA2DS2-VASc score of 8) suffered a stroke and one 78-year-old man (CHA2DS2-VASc score of 7) suffered a TIA (transient ischemic attack). Both were on warfarin within therapeutic range (INR of 2.41 and 2.63 respectively) at the time of their event. A total of 13 symptomatic ischemic events (mainly strokes and TIAs) occurred during the entire follow-up – all in patients having a CHA2DS2-VASc score greater than 2.

The researchers conclude that properly conducted ECV is associated with a high acute success rate and low complication rates. However, long-term success declines dramatically in patients having been in persistent AF for more than 6 months prior to their cardioversion.
Toso, E, et al. Electrical cardioversion of persistent atrial fibrillation: acute and long-term results stratified according to arrhythmia duration. PACE, Vol. 35, September 2012, pp. 1126-34