Proactive esophageal cooling protects against thermal insults during high-power short-duration radiofrequency cardiac ablation

Abstract

Background: Proactive cooling with a novel cooling device has been shown to reduce endoscopically identified thermal injury during radiofrequency (RF) ablation for the treatment of atrial fibrillation using medium power settings. We aimed to evaluate the effects of proactive cooling during high-power short-duration (HPSD) ablation.

Methods: A computer model accounting for the left atrium (1.5 mm thickness) and esophagus including the active cooling device was created. We used the Arrhenius equation to estimate the esophageal thermal damage during 50 W/ 10 s and 90 W/ 4 s RF ablations.

Results: With proactive esophageal cooling in place, temperatures in the esophageal tissue were significantly reduced from control conditions without cooling, and the resulting percentage of damage to the esophageal wall was reduced around 50%, restricting damage to the epi-esophageal region and consequently sparing the remainder of the esophageal tissue, including the mucosal surface. Lesions in the atrial wall remained transmural despite cooling, and maximum width barely changed (<0.8 mm).

Conclusions: Proactive esophageal cooling significantly reduces temperatures and the resulting fraction of damage in the esophagus during HPSD ablation. These findings offer a mechanistic rationale explaining the high degree of safety encountered to date using proactive esophageal cooling, and further underscore the fact that temperature monitoring is inadequate to avoid thermal damage to the esophagus.

Keywords: Atrial fibrillation; atrioesophageal fistula; esophageal cooling; mathematical modeling; radiofrequency ablation.

Figure 1

a) Physical situation to be modeled with an active cooling device located in the esophageal lumen. b) Model geometry including RF catheter, tissues near the ablation site and an active cooling device located in the esophageal lumen. The evaluation line (black line) for post-processing is shown across the ablated tissues, from tip of RF catheter to edge of active cooling device (with tissues including myocardium, fat and esophagus).

Figure 2

General view (a) and zoom-in (b) of the meshing around the electrode with 162,322 total elements and 102,250 around the catheter electrode. The color legend represents skewness element quality. Histograms of element quality around the electrode showing the skewness (c), volume versus length (d), and growth rate (e).

Figure 3

Progress of electrical variables (power, impedance, current and voltage) during RF pulse using 50W/10s (top) and 90W/4s (bottom). Note that power is almost constant during the RF pulse, with variations less than 2 W.

Figure 4

Temperature distributions during HPSD ablation using 50W/10s and 90W/4s, with (protection) and without (control) proactive esophageal cooling (scale in °C).

Figure 5

Temperature progress computed at different locations below the electrode during and after RF pulse for 50W/10s and 90W/4s, with (protection) and without (control) proactive esophageal cooling. Device wall and cooling water correspond to esophageal tissue in the control case in which no esophageal thermal cooling is used.

Figure 6

Lesion shapes (computed with fraction of damage θ_d = 63% after 90 s with the Arrhenius model) for 50W/10s and 90W/4s, with (protection) and without (control) proactive esophageal cooling.

Figure 7

Esophageal lesion transmurality (A) and maximum lesion width in the myocardial wall (B) computed with two fractions of damage θ_d (63% and 99%) just after the RF pulse and after 90 s, for 50W/10s and 90W/4s, and with (Protection) and without (Control) proactive esophageal cooling.