Clinical studies have shown that transthoracic
cardioversion of
atrial fibrillation is dependent on achieving adequate current flow to the heart, which is dependent on transthoracic impedance. When multiple standard
cardioversion fails to restore sinus rhythm in patients with
atrial fibrillation the double sequential transthoracic
shock may be an alternative.
METHODS AND RESULTS: Twenty one consecutive patients with paroxysmal or
persistent atrial fibrillation refractory to at least two initial high energy 360 J or 200-300 and 360 J monophasic shocks underwent double sequential shocks with 720 J by means two
defibrillators. Mean age was 64 +/- 11 years and mean weight 97 +/- 19 kg (range, 49 to 112). Duration of
atrial fibrillation was present < or = 3 months in 76%. Arterial
hypertension was present in 38% and lone
atrial fibrillation in 33%. Mean left atrial size was 4.5 +/- 0.7 cm (range, 3.5 to 6.0). Sinus rhythm was achieved in 19 (90.4%). Two refractory to biphasic shocks with a median 1,050 J (range, 660 to 1,440 J) without major complications. Multivariate analysis identified duration of
atrial fibrillation, > 90 days (RR 0.96, CI 0.95-0.98 p = 0.02) and
body weight, 101 +/- 11 kg (RR 0.64, CI 0.46-0.90 p = 0.01) variables independently associated with
cardioversion unsuccessful. Patient weight, p = 0.002 was the univariate predictor of unsuccessful
cardioversion. High energy
cardioversion does not cause cardiac damage evidenced from cardiac
troponin T estimation.
CONCLUSION: