Can biphasic rectilinear external cardioversion of atrial fibrillation be compared to biphasic intracardiac cardioversion ?

Purpose of Study: According to some papers, the effectiveness of intracardiac electrical cardioversion approaches 100 % and is generally

considered to be a „gold standard“ in the effectiveness of electrical cardioversion of atrial fibrillation to sinus rhythm. Findings

from experimental papers and experience from the practice suggest that the effectiveness of intracardiac biphasic cardioversion is

closely approached by that of some external biphasic defibrillators. Our aim was to try to determine whether in our cohort of patients

with persistent atrial fibrillation presenting for external biphasic rectilinear electrical cardioversion, performing intracardiac electrical

cardioversion would be beneficial in those with ineffective external biphasic rectilinear electrical cardioversion.

Methods: In a cohort of 419 patients, in whom a total of 622 external electrical cardioversions were performed using a rectilinear biphasic

defibrillator, data on the procedures performed between July 2001 and December 2007 were collected both retrospectively and

prospectively and further statistically processed. Both individual and cumulative effectiveness of the shocks delivered in version to sinus

rhythm (SR), the relation between the energy, current and success rate of version to SR, and the actual energy and current levels delivered

by the defibrillator were observed. In a group of 40 patients with ineffective cardioversion and persistent atrial fibrillation, intracardiac

electrical cardioversion was indicated. Only seven patients gave their consent to the procedure. The effectiveness of cardioversion, the

energy levels of individual shocks, and cumulative energy were evaluated.

Results: The cumulative effectiveness of external electrical cardioversion with biphasic rectilinear shock in restoring sinus rhythm

reached 93.6 % in our observation. The effectiveness increased with the number and predetermined energy of the shocks (the energy actually delivered is shown in the parentheses) from 46.2 % at the first shock of an average energy of 66.3 (85.4) J to 82.5 %

at the second shock of an average energy of 115.7 (147.3) J to 93.6 % at the third shock of an average energy of 175 (218) J. Thus, on

average, 357 (450.7) J of energy were used cumulatively. Shocks leading to restoring a normal SR had significantly lower impedance

levels (p < 0.0001), significantly higher current levels (p < 0.0001), and significantly higher levels of the energy predetermined and

delivered (p < 0.0001). A significant decrease in impedance was demonstrated at the second shock compared to the impedance at the

first shock (p < 0.0001). Out of the seven patients who underwent intracardiac electrical cardioversion, SR was achieved in only three

(42.9 %, p = 0.001); two developed recurrent AF within a week after the procedure, and one did within an hour after the procedure.

All the patients required three escalating shocks according to the protocol (5–10–15 J) with a cumulative energy of 30 J. The group

of patients with intracardiac cardioversion had a significantly higher chest impedance compared to that in the group with external

cardioversion (p = 0.017).

Conclusions: Our experience with more than 600 external electrical biphasic cardioversions shows that, given the high effectiveness

of a biphasic external shock approaching 94 %, further indication for intracardiac biphasic cardioversion is questionable due to its relatively

low efficacy (3 out of 7 patients).

Keywords: atrial fibrillation, biphasic cardioversion, external cardioversion, internal cardioversion.