Background: Synchronized direct current cardioversion (DC) is widely used for atrial fibrillation (AF) conversion to sinus rhythm. With the purpose to identificate the optimal procedure for the effective DC of AF, we compared the results obtained following traditional free-multiple shock sequence to simple two-shock sequence in two groups of adults with underlying heart disease submitted to elective DC for AF in our Dept. of Cardiology.
Methods: The first group, retrospectively considered, included 84 episodes of AF occurred in 79 patients. DC started on an energy level of 100 joules (J) and, when unsuccessful, repeated on increasing levels, from 150J to 360J, depending on physician preference. An additional shock of 360J was always delivered when the last shock-dose proved to be ineffective. The second group, prospectively considered, included 61 episodes of AF occurred in 61 patients. The protocol provided for an initial shock of 200J followed, when necessary, by a second one of 360J and no additional shocks.
Results: Conversion rate (86.9% vs. 85.2%) showed no statistical difference (p = NS) between groups. Following the two-shock protocol, a significant reduction of the mean amount of energy used for effective conversion (258.5J vs. 345.0J; p < 0.001), of the mean amount of total energy delivered to patients (302.9J vs. 439.6J; p < 0.001), particularly to non responders (560.0J vs. 1067.2J; p < 0.0001) was found. Using the first procedure only 13.1% of patients were cardioverted delivering 100J and 35.8% of them needed additional 200J. In the second group, the initial shock of 200J cardioverted 54.1% of patients. In both studies no patients had adverse effects either during or early after DC or during the four-week follow-up, where haemorrhagic and thromboembolic complications has been also considered.
Conclusions: Two-shock protocol seems to provide better success/total energy delivered ratio, to reduce the total amount of energy delivered to each patient and to shorten the DC procedure when compared to free-multiple shock sequence usually performed, reducing the total time of anesthesia.