Our trust recently replaced our defibrillators with the Zoll R Series Plus. This has a rectilinear biphasic waveform. Compared with traditional energies used with monophasic waveforms, the Zoll literature recommends lower energies for synchronised DC cardioversion of arrhythmias, starting at 75J (75J, 120J, 150J, 200J), based upon the results of clinical trials; the recommendations are to use 120J if the BMI is significantly elevated. When we switched across to the new defibrillators using the recommended protocol, we noticed a lack of first shock efficacy, and sought to compare the efficacy of the recommended protocol with a simpler protocol of up to 3 200J synchronised shocks using the same device by undertaking a service evaluation.
18 consecutive patients who underwent DCCV of atrial fibrillation using the Zoll Protocol (75J or 120J initial shock) were compared with 18 consecutive patients using the New Protocol (200J initial shock).
The demographics were as per Table 1. Patients undergoing the New Protocol were significantly more likely to have had more than one previous cardioversion, but otherwise the groups were well matched. 16 patients started at 75J in the Zoll Protocol group and 2 at 120J. Overall, 17/18 had a successful cardioversion using the Zoll Protocol and 18/18 had a successful cardioversion using the New Protocol (p=ns). There were on average 2.0 shocks per patient in the Zoll Protocol group (36 in total) vs 1.2 shocks per patient in the New Protocol group (21 in total). The first shock efficacy was significantly lower in the Zoll Protocol group (8/18 vs 16/18, p=0.005, Table 1). There were no safety issues
In conclusion, using a higher initial starting energy rather than the recommended settings reduces the number of shocks delivered to patients to achieve cardioversion, and made running a cardioversion list more efficient. No safety issues were encountered.