To the Editor:
We thank Drs. Luis Tercedor and Miguel Álvarez for the interest they showed in our article «Effectiveness of Scheduled Cardioversion in Atrial Fibrillation. Comparison of Two Schemes of Treatment: Electrical Cardioversion versus Pharmacological Cardioversion,» recently published in Revista Española de Cardiología.1 However, we would like to clarify certain points and address some of the considerations in their commentaries.
In the first place, it should be noted that, as mentioned in the article, the study was a comparative study of two consecutive series of patients who underwent cardioversion, pharmacological cardioversion at one hospital and electrical cardioversion at another. Therefore, it is a registry of cardioversions carried out at two hospitals in our community, with the limitations that this involves.
On the one hand, although the high success rate in the quinidine group, superior to that described in earlier studies,2 may seem surprising, other series have reported similar success rates, in some case over 85%.3,4 These results are from uncontrolled studies, but similar results have been found for amiodarone5 and flecainide6 in comparative studies. It should be emphasized that in our study the hospital where quinidine cardioversion was performed has extensive experience in the management of this drug. This type of cardioversion has been performed for 10 years with scant complications, as described in the article. This long experience may have been responsible for the good results. On the other hand, the complication rate found in the pharmacological group (1.16%), although low, is similar to the rate reported in some published series. It should be remembered that the meta-analysis of Southworth et al7 encountered a mortality rate similar to that of other antiarrhythmic drugs considered «safer.» In our study, the patients treated with quinidine remained hospitalized throughout treatment. At this time (the first 72 hours) is when the highest incidence of arrhythmias is reported.8 Only one case of symptomatic torsade de pointes was recorded, which was resolved without consequences for the patient. It is possible that the real frequency of arrhythmic complications is underestimated when patients are not being controlled electrocardiographically; however, it is logical to think that all the symptomatic complications were detected. It is possible that some patient had an asymptomatic and, therefore, undetected arrhythmic episode, but its clinical meaning is dubious at best. It has been reported that the proarrhythmic effects of quinidine, although idiosyncratic, are associated with depressed systolic function. The series that we presented consisted of patients with conserved systolic function. In any case, the fundamental problem of proarrhythmia is the long-term treatment, rather than acute treatment to achieve cardioversion, since the patient is hospitalized.
The effectiveness of electrical cardioversion was similar to what would be expected from the literature.9 In most series, 15%-25% of cardioversions are ineffective, so interventions and methods have been tried in an attempt to obtain better results. As Tercedor and Álvarez point out, the use of an alternative paddle position or greater discharge energy could have increased its effectiveness. Nevertheless, at the time when the patients´ data were being collected, the protocol followed in our hospital was the one described (anteroapical electrode position). Our group has considered this problem and in recent years we have made several studies to try to increase this percentage. In a prospective series of 89 patients with persistent atrial fibrillation studied in our hospital (unpublished data), two different electrode positions were compared randomly (anteroapical versus anteroposterior), but no significant differences were found in the success rate (81% versus 85%, respectively). No differences were found in the total or maximum energy required, number of shocks, and impedance values between the different electrode positions. Likewise, no significant correlations were found among the values of impedance and weight, body mass index, or body surface. In both groups the programmed energy was 200, 300, 360, and 360 J (higher than that used in our study), but the success rate, although slightly higher, was not significantly greater. We have not found that the administration of intravenous flecainide immediately before electrical cardioversion improves its effectiveness in a series of 53 patients with persistent atrial fibrillation10 (73% success in the flecainide group versus 85% in the control group).
To conclude, our objective was not to recommend the systematic use of quinidine which we know has a series of limitations that are discussed in our article (like a longer mean stay) but to remind readers that other alternatives to electrical cardioversion exist, which are often as effective as electrical cardioversion and whose use is conditioned by experience with the drug used.