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Encircling overlapping multipulse shock waveforms for transthoracic defibrillation

^a Department of Internal Medicine, University of Iowa Hospital, Iowa City, Iowa, USA

View larger version (26K): [in a new window]   Figure 1 Study 1. Electrode positions on the thorax (1–6), and electrical current vectors (a–k) for the encircling overlapping waveform. The thorax is represented as a circle with the heart in the middle. Vectors a, c, e, g, i and k result from an electrical pulse generated by a single-capacitor discharge and flowing between a single pair of electrodes (e.g., electrodes 1–4, pathway 1). Electrical pulses 4, 5 and 6 flow between the same electrode as pulses 1, 2 and 3 but are reversed in polarity. Vectors b, d, f, h and j result from the overlapping discharge of two capacitors yielding pulses flowing between two pairs of electrodes simultaneously (e.g., 1–4 and 2–5), with the mean electrical vector lying between the two pathways defined by the two electrode pairs. Each electrical vector is of equal duration. The damped sinusoidal and biphasic shocks were always given utilizing pathway 2 (pads 2–5).

View larger version (21K): [in a new window]   Figure 2 Study 2. Electrode positions on the thorax (1–6), electrical current vectors (a–g) and timing of the multiple overlapping electrical pulses. EO6 = encircling overlapping six-electrode shocks. EO3 = encircling overlapping three-electrode shocks. Note that this EO6 waveform has only seven vectors as opposed to the 11 vectors of the EO6 waveform in Study 1.

View larger version (14K): [in a new window]   Figure 3 Study 1. Graph showing percent shock success of encircling overlapping 6-electrode (EO6) shocks, biphasic (Bi) shocks and damped sinusoidal (DS) shocks. The EO6 waveform shocks achieved higher success rates than both Bi and DS waveforms at energies of 18–99 J, and higher than DS at energies up to 149 J.

View larger version (16K): [in a new window]   Figure 4 Study 2. Percent shock success of encircling overlapping six-electrode (EO6) and three-electrode (EO3) shocks, as well as biphasic (Bi) and damped sinusoidal (DS) shocks. EO6 and EO3 shock success rates were equal at all energy levels. *p < 0.05 vs. DS + p < 0.05 vs. Bi n = 11 swine.