Some factors affecting bubble formation with catheter-mediated defibrillator pulses.

Factors affecting bubble formation during delivery of defibrillator pulses to arrhythmogenic cardiac tissue via a catheter are unknown. We investigated the role of energy, electrode surface area, interelectrode distance, and electrode polarity on bubble formation and on current and voltage waveforms during delivery of damped sinusoidal discharges from a standard defibrillator to anticoagulated bovine blood. Gas composition was studied with mass spectrometry. Defibrillator energy settings were varied between 5 and 360 J. The principal catheter used for study was a Medtronic 6992A lead. Additional electrodes tested included 2, 5, and 10 mm long No. 6F, 7F, and 8F copper electrodes. Interelectrode distances used to assess the effect of anode-cathode spacing were 1, 5, 10, and 20 cm. Bubble volume increased linearly from 0.043 to 0.134 ml per cathodal pulse and from 0.030 to 3.50 ml per anodal pulse as energy settings were increased from 5 to 360 J (r = .99). Typical smooth waveforms for both current and volt...