TESTING DIFFERENT BIPHASIC WAVE-FORMS AND CAPACITANCES - EFFECT ON ATRIAL DEFIBRILLATION THRESHOLD AND PAIN PERCEPTION

Objectives. The goal of this study was to compare the effect of differ ent tilts and capacitances for biphasic shocks on atrial defibrillatio n efficacy and pain threshold. Background. Although biphasic shocks ha ve been shown to be superior to monophasic shocks, the effect of tilt and capacitance on atrial defibrillation success and pain perception h as not been studied in patients. Methods. Atrial defibrillation thresh old (DFT) testing was performed using a right atrial appendage/coronar y sinus lead configuration in 38 patients with a history of paroxysmal atrial fibrillation undergoing an invasive electrophysiologic study. Biphasic waveforms with 40%, 50%, 65%, 80%, 30%/50% and 40%/50% were t ested randomly in 22 patients (Group 1). In 16 patients (Group 2), a 6 5% tilt waveform with 50- and 120-mu F capacitance was tested. Before sedation, pain sensation was graded by 15 patients in Group 1 after de livery of a 0.5-J shock and by 10 patients in Group 2 after two 1.5-J shocks with 50 and 120-mu F capacitance were delivered. Results. The D FT energy for the 50% tilt waveform was significantly lower than the 6 5%, 80% and 30%/50% tilt waveforms. The 40%/50% tilt waveform provided slightly lower energy requirements than the 50% tilt waveform. Nine p atients (60%) described the 0.5-J shock as very painful, and four (26. 6%) complained of slight pain. The 50-mu F capacitor lowered energy re quirements compared with the 120-mu F capacitor. Six patients (60%) pe rceived the 1.5-J 50-mu F capacitor shock as more painful, whereas thr ee (30%) perceived both shocks as equally painful. Conclusions. Biphas ic waveforms with 50% tilt in both phases and a smaller tilt in the po sitive phase than that in the negative phase (40%/50%) provided a decr ease in energy requirements at atrial DPT. In addition, stored energy was reduced by biphasic shocks with 50-mu F capacitance compared with 120-mu F capacitance. Despite the reduction in energy requirements, sh ocks <1 J continued to be perceived as painful in the majority of pati ents.