Predicting Electrical Cardioversion Failure
May 1, 2017 4 minutes read
By Michael H. Crawford, MD
Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco
Dr. Crawford reports no financial relationships relevant to this field of study.
SYNOPSIS: A study of the 30-day success rate of electrical cardioversion of acute atrial fibrillation revealed five clinical predictors of recurrence. These were combined into a risk score that could be useful to avoid unnecessary cardioversions in the acute setting.
SOURCE: Jaakkola S, Lip GY, Biancari F, et al. Predicting unsuccessful electrical cardioversion for acute atrial fibrillation (from the AF-CVS score). Am J Cardiol 2017;119:749-752.
Electrical cardioversion (ECV) of atrial fibrillation (AF) is not always successful and exposes patients to thromboembolism when anticoagulation is inadequate. Thus, investigators from the FinCV study sought to derive and validate a clinical scoring system to predict ECV failure and early AF recurrence in acute AF patients (< 48 hours). This was a retrospective study of first EVCs in 2,868 patients with acute AF presenting to one of three Finnish hospitals and followed for 30 days after ECV. The population was divided into two cohorts: derivation (Western Finland) and validation (Eastern Finland). Failure was defined as unsuccessful ECV or recurrence in 30 days. A multivariate analysis of clinical variables believed to be associated with persistence of AF was performed on the derivation set and resulted in five independent variables: age group (< 45 years, 45-65 years, and > 65 years), not their first AF episode, congestive heart failure, vascular disease (coronary, peripheral, or aortic), and more than one month since prior episode. Points were assigned to each variable to derive an AF-CVS (acronym for the five factors, see Table 1) score. The overall AF event rate was about 40% in both cohorts. Those with < 3 points exhibited low failure rates (1.3-13%) and with > 5 points high rates (34-67%). The lowest rate was seen in young men (< 45 years) experiencing their first AF event (0-6% in both cohorts). The C-statistic for the AF-CVS score was 0.67. The accuracy of the AF-CVS score was independent of the use of antiarrhythmic drugs. The authors concluded that five simple clinical factors can predict the early failure of ECV in acute AF patients.
COMMENTARY
Rapid cardioversion of new AF patients in the ED is becoming more popular as hospitals try to limit admissions to higher reimbursed patients. Also, ED doctors appreciate the extra procedural income. However, repeated ECV can result in prolonged atrial stunning and increase the risk of thromboembolism. Thus, it would be useful to create a method of identifying patients less likely to experience recurrent AF after ECV. This study is the first attempt to develop a risk tool for recurrent AF after acute ECV.
The major determinants of early recurrence are a short interval from a prior episode of AF and experiencing a prior episode in general. The other three factors are components of the CHA2DS2-VASc score. Interestingly, sex, which is important in the CHA2DS2-VASc score, did not quite make significance in this study (female sex, P = 0.065). The AF-CVS has a C-statistic of 0.67, which is similar to that of the CHA2DS2–VASc score.
Recurrence of AF in 30 days was about 40%, which may be an underestimation since patients were not monitored for asymptomatic events. This score only is applicable to patients with acute AF of < 48 hours duration. Recurrences after longer time intervals may have different predictors, such as left atrial size. Previous studies have shown that the use of antiarrhythmic drugs and beta-blockers reduces recurrences. Although antiarrhythmic drug use was evaluated in this study, it did not affect the accuracy of the AF-CVS score. Older literature has identified the ECG characteristics of AF as a predictor of recurrence. Those with coarse AF waves on the ECG were less likely to recur than those with very fine waves. This may have something to do with the health of the atria. ECG characteristics were not evaluated in this study. Despite these limitations, I believe this score will be useful for identifying the appropriate candidates for acute ECV in the ED.
Table 1. Calculating the AF-CVS Score |
||
|
Factors |
Points |
Hazard Ratio |
|
Age 45-65 years |
1 |
1.31 |
|
> 65 years |
2 |
1.31 |
|
not First AF episode |
2 |
1.55 |
|
Congestive heart failure |
2 |
1.52 |
|
Vascular disease |
1 |
1.38 |
|
Short interval from prior AF |
3 |
2.31 |
A study of the 30-day success rate of electrical cardioversion of acute atrial fibrillation revealed five clinical predictors of recurrence.
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