Beta-receptor blockade in maintenance of sinus rhythm obtained by electroconversion

Early recurrences of atrial fibrillation after electrical cardioversion: a result of fibrillation-induced electrical remodeling of the atria?

OBJECTIVES

We sought to investigate whether, in humans, the timing and incidence of a relapse of atrial fibrillation (AF) during the first month after cardioversion indicates the presence of electrical remodeling and whether this could be influenced by prevention of intracellular calcium overload during AF.

BACKGROUND

Animal experiments have shown that AF induces shortening of the atrial refractory period, resulting in an increased vulnerability for reinduction of AF. This electrical remodeling was completely reversible within 1 week after cardioversion of AF and was presumably related to intracellular calcium overload.

METHODS

Using transtelephonic monitoring in 61 patients cardioverted for chronic AF, we evaluated the daily incidence of recurrence of AF and determined, by Cox regression analysis, the influence of patient characteristics and medication on relapse of AF.

RESULTS

During 1 month of follow-up, 35 patients (57%) had a relapse of AF, with a peak incidence during the first 5 days after cardioversion. Furthermore, in patients with a recurrence of AF, there was a positive correlation between the duration of the shortest coupling interval of the premature atrial beats after cardioversion and the timing of the recurrence of AF (p = 0.0013). Multivariate analysis revealed that the use of intracellular calcium-lowering drugs during AF was the only significant variable related to maintenance of sinus rhythm after cardioversion (p = 0.03).

CONCLUSIONS

The daily distribution of recurrences of AF suggests a temporary vulnerable electrophysiologic state of the atria. Use of intracellular calcium-lowering medications during AF appeared to reduce recurrences, possibly due to a reduction of electrical remodeling during AF.

Prophylactic treatment after electroconversion of atrial fibrillation

Atrial fibrillation is a common arrhythmia. Sinus rhythm can often be restored by electroconversion, but the relapse rate is high. Various antiarrhythmic drugs have been used to maintain sinus rhythm after electroconversion. This article reviews the experience with these drugs and suggests a treatment strategy.

Maintenance of sinus rhythm after atrial defibrillation

The long-term results of 356 episodes of atrial defibrillation by DC shock carried out in 250 patients are reviewed. In 78 per cent of the cases, atrial fibrillation recurred by the end of 12 months in spite of the administration of quinidine or procainamide or propranolol, singly or combined. However, when no antidysrhythmic drugs were used the recurrence rate was higher at all periods of observation and 100 per cent at the end of 12 months. The difference in the overall results between the untreated group and the treated groups with the exception of the propranolol group is significant (p less than 0.05). In addition, the propranolol group showed an obviously reduced recurrence rate at 1 month, but afterwards the results tended to approximate those in the untreated group. The period during which sinus rhythm could be maintained in patients who underwent valve operations was on the whole the same as in patients who did not have heart surgery. However, in a small number of patients sinus rhythm was maintained for longer periods after mitral valve replacement than before it. Sinus rhythm was maintained for significantly longer periods when atrial fibrillation lasted less than 1 year than when it had been present for more than 1 year (p less than 0.001). It is concluded that there is justification for a judicious antidysrhythmic prophylaxis after atrial defibrillation.