OBJECTIVES The aim of the study was to evaluate the effects of intravenous
(IV) flecainide on defibrillation energy requirements in patients treated w
ith low-energy internal atrial cardioversion.
BACKGROUND Internal cardioversion of atrial fibrillation is becoming a more
widely accepted therapy for acute episode termination and for implantable
atrial defibrillators.
METHODS Twenty-four patients with atrial fibrillation (19 persistent, 5 par
oxysmal) underwent elective transvenous cardioversion according to a step-u
p protocol. After successful conversion in a drug-free stale, atrial fibril
lation was induced by atrial pacing; IV flecainide (2 mg/kg) was administer
ed and a second threshold was determined. In patients in whom cardioversion
in a drug-free state failed notwithstanding a 400- to 550-V shock, a thres
hold determination was attempted after flecainide.
RESULTS Chronic persistent atrial fibrillation was converted in 13/19 (68%)
patients at baseline and in 16/19 (84%) patients after flecainide. Paroxys
mal atrial fibrillation was successfully cardioverted in all the patients.
A favorable effect of flecainide was observed either in chronic persistent
atrial fibrillation (13 patients) or in paroxysmal atrial fibrillation (5 p
atients) with significant reductions in energy requirements for effective d
efibrillation (persistent atrial fibrillation: 4.42 +/- 1.37 to 3.50 +/- 1.
51 J, p < 0.005; paroxysmal atrial fibrillation: 1.68 +/- 0.29 to 0.84 +/-
0.26 J, p < 0.01). In 14 patients not requiring sedation, the favorable eff
ects of flecainide on defibrillation threshold resulted in a significant re
duction in the scores of shock-induced discomfort (3.71 +/- 0.83 vs. 4.29 /- 0.61, p < 0.005). No ventricular proarrhythmia was observed for any shoc
k.
CONCLUSIONS Intravenous flecainide reduces atrial defibrillation threshold
in patients treated with low-energy internal atrial cardioversion. This red
uction in threshold results in lower shock-induced discomfort. Additionally
, flecainide may increase the procedure success rate in patients with chron
ic persistent atrial-fibrillation. (C) 1999 by the American College of Card
iology.