Initial energy for biphasic external electrical cardioversion of atrial fibrillation.

Background: No international guidelines indicate the initial energy in biphasic external electrical cardioversion of atrial fibrillation (AF) actually. The aim of this study was to determine this value in order to find a reasonable compromise between the necessity of limiting tissue damage and of quickly restoring sinus rhythm as well.

Methods: Fifty-six consecutive patients with AF candidate to external electrical cardioversion were treated using adhesive anterior-posterior paddles and biphasic wave defibrillator Lifepack 12, with steps of 50 J. After 6 hours troponin I levels were measured.

Results: Thirty-four patients were cardioverted by 50 J (group A), 18 by 100 J (group B) and 3 by 150 J (group C). One patient was not cardioverted (success rate 98%). No significant differences were noted between groups A and B with regard to age, sex, weight, height, thoracic circumference, body mass index, body surface area, impedance, NYHA class, left ventricular ejection fraction, left atrial diameter, causes of heart disease, antiarrhythmic medications, and duration of current AF episode. No increase of troponin I levels occurred.

Conclusions: An initial shock of 100 J in the biphasic external elective cardioversion of AF is a valid and highly effective option. An initial shock of 50 J was effective in 61% of our population, and it is probably appropriated in patients with a lower weight and body mass index.