Atrial Fibrillation After Electrical Cardioversion
ABSTRACT & COMMENTARY
Synopsis: The influence of intracellular calcium- lowering agents on electrical remodeling of the atrium during atrial fibrillation has a favorable influence on maintenance of sinus rhythm after cardioversion.
Source: Tieleman, RG. J Am Coll Cardiol 1998;31: 167-173.
Tieleman and colleagues studied the pattern of recurrence of atrial fibrillation after electrical cardioversion. The authors performed transthoracic electrical cardioversion in 61 patients with atrial fibrillation. The median duration of atrial fibrillation was seven months. More than two-thirds of the patients had some form of structural heart disease, with the remaining one-third having "lone atrial fibrillation." Sixteen of the patients were receiving antiarrhythmic drugs before the cardioversion, and 32 received antiarrhythmic medications after cardioversion. The remaining patients were just treated with anticoagulation and AV nodal blocking agents including digitalis, calcium channel blockers, or beta adrenergic blockers alone or in combination. After cardioversion, the patients were followed with daily transtelephonic ECG transmissions to document recurrence of atrial fibrillation. AV nodal blocking agents for rate control were continued after cardioversion. Antiarrhytmic therapy was at the discretion of the primary physicians. Tieleman et al then identified 35 of the 61 patients (57%) who had a relapse into atrial fibrillation. They then examined clinical, pharmacologic, echocardiographic, and electrophysiologic predictors of atrial fibrillation recurrence.Most standard clinical variables did not predict recurrence. There was no statistically significant difference in recurrence rate predicted by the presence or type of heart disease, New York Heart Association functional class, or echocardiographic variables. Duration of arrhythmia also was not a predictor in this cohort of patients with relatively recent onset arrhythmia. Multivariate analysis revealed that the use of intracellular calcium-lowering drugs during atrial fibrillation before cardioversion was the only significant variable related to the maintenance of sinus rhythm during the period of study. In this article, both calcium channel blocking drugs and beta blocking drugs were considered to be intracellular calcium-lowering drugs. Tieleman et al also note a relationship between the timing of atrial premature beats and the timing of recurrence. Most recurrences of atrial fibrillation occurred in the first five days after conversion. A total of 22 of the 35 (63%) recurrences occurred within this time window. Patients who had early coupled APBs noted immediately after cardioversion were likely to recur early, while patients who had late coupled APBs fell in the group who reverted later. However, the occurrence of atrial premature beats was not predictive of whether the patients would recur.
Tieleman et al suggest that the influence of intracellular calcium-lowering agents on electrical remodeling of the atrium during atrial fibrillation has a favorable influence on maintenance of sinus rhythm after cardioversion. Although this was a nonrandomized, noncontrolled study, they argue that the observations in this study should generate further clinical trials on the value of these agents.
COMMENT BY JOHN P. DiMARCO, MD, PhD
Electrical cardioversion is almost always successful in restoration of atrial fibrillation to acute sinus rhythm. The major problem has been long-term maintenance of sinus rhythm. Recently, the phenomena of electrical remodeling of the atrium during atrial fibrillation have been described. During atrial fibrillation, there is a change in the electrophysiologic properties of atrial myocardium, including changes in atrial refractory period and other parameters that predispose toward recurrence and persistence of atrial fibrillation. Human and animal data have suggested that this electrical remodeling can be at least partially blocked by administration of calcium channel blocking agents while the patient is in atrial fibrillation. This is the first clinical study that gives further support to this observation.These observations require confirmation in a carefully designed clinical trial. However, even now, I believe that the data presented here are powerful enough to support use of either a calcium channel blocking drug or a beta blocking drug in preference to digitalis monotherapy in patients for rate control before a planned cardioversion. These agents may show better control of heart rates during exercise and, as shown in this study, may have additional benefits after cardioversion for subsequent maintenance of sinus rhythm.
It will be interesting in the future to see if there is a true difference between calcium channel blockers and beta blockers. It would also be interesting to see if the lower recurrence is merely a phenomenon of better rate control before cardioversion or if a lower recurrence rate really is the result of a beneficial effect on electric remodeling.
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