Bipolar ablation’s unique paradigm: Duration and power as respectively distinct primary determinants of transmurality and steam pop formation

Figures

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  Figure 1. A: The ex vivo bipolar ablation model setup, including a custom sample holder to ensure repeatable catheter alignment and placement, irrigated ablation catheters (TactiCath; Abbott, St. Paul, MN), an intracardiac echocardiography (ICE) catheter (Abbott), and a saline heater and circulator, all housed in a saline bath. B: Generator connection for bipolar ablation.

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  Figure 2. Catheter orientations for both the perp-configuration, in which the active catheter was perpendicular to the tissue (and the indifferent catheter was parallel), and the para-configuration, in which the active catheter was parallel to the tissue (and the indifferent catheter was perpendicular).

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  Figure 3. Images of representative samples with low transmurality (A) and high transmurality (B). The forceps indicate the first ablation in each set of 3. The measurements labeled 1, 2, and 3 in panel A denote how lesion width, lesion depth, and tissue length were measured in ImageJ (National Institutes of Health, Bethesda, MD), respectively. In general, with all other variables held constant, longer ablation times led to greater transmurality.

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  Figure 4. Analysis of the transmurality (left axis) and the frequency of steam pops (right axis) among different ablation settings and parameters. The analysis was carried out on 72 different ablations for the perp-configuration and on 24 ablations for the para-configuration. For each combination of settings, the total number of steam pops over 3 samples is represented in the secondary y-axis (black dots). Overall, steam pops were more frequent with higher power settings.

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  Figure 5. A: Intracardiac echocardiography images of steam pop formation over the course of a 40-W, 20g, 60-second ablation. The blue arrow indicates the area of steam pop formation. Supplementary Video 1 further shows this formation. B: Myocardial damage resulting from the steam pop, indicated by the forceps in the image.