Abstract 13330: Steam Pop Prediction and Detection During Radiofrequency Ablation

Introduction: Steam pops can occur during RF ablation when tissue temperatures exceed 100 C. While tactile and audible cues are used for their detection, background lab noise and catheter movement may confound identification. The EnSite™ Contact System measures, as an Electrical Coupling Index (ECI), both resistive and reactive impedance between the ablation catheter and tissue. ECI is displayed as a continuous waveform during ablation. The objective of this study was to determine if ECI could aid in steam pop detection and prediction. Methods: Power control RF ablation lesions (30 - 50 W, 60 s, n = 160) were created in the RA, LA, and RV of 13 swine using a 4 mm open irrigated RF ablation catheter. A Millar catheter placed in the RA or aorta and a digital stethoscope placed on the chest wall served as gold standards for steam pop detection: simultaneous spikes on traces from both devices defined a steam pop. Conventional steam pop detection was compared to the gold standard in 6 swine. The prediction capability of a previously derived steam pop prediction algorithm using ECI components plus conventional parameters was also tested. Data collected included the time of steam pop, power, duration, temperature, and impedance from the RF generator and ECI. Results: Steam pops occurred in 25 lesions causing cardiac tamponade in 2 swine. Mean time to pop was 28 ± 16 s. Tactile and audible cues identified only 67% of steam pops. For these, even when pops were barely audible, ECI deviations were always clear and confirmatory. All the non-perceived pops occurred in the atria. The steam pop prediction algorithm accurately predicted 92% of all steam pops at least 3 s before they occurred, including all of the non-perceived pops. The negative predictive value of the steam pop prediction algorithm was 98%. Conclusions: The incidence of steam pops in the atria is higher than typically appreciated using conventional means. ECI may be a useful tool for both steam pop detection and prediction.