title: Occurrence of steam pops during irrigated RF ablation: novel insights from microwave radiometry.
abstract: BACKGROUND
  The disparity between catheter and tissue temperatures during irrigated RF ablation frustrates one's ability to predict steam pops. Microwave radiometry allows for "volumetric" temperature assessment-i.e., within a circumscribed volume around the catheter tip-permitting, direct assessment of temperature during ablation. The aim of this study was to examine (i) the ability of microwave radiometry to predict steam pops, and (ii) compare this to traditional parameters such as power, catheter temperature, and impedance.
  
  
  RESULTS
  Irrigated RF ablation was performed in 8 sheep using the Tempasure ablation catheter in all chambers. Power, impedance, catheter tip, and volumetric temperature were continually monitored. Ablation was terminated after a pop or at 60 seconds. A pop was defined as an audible or visualized pop (intracardiac echocardiography). Predictors of pops were determined by univariate and multivariate GEE logistic regression modeling. A total of 48 pops occurred during 143 lesions applied at 20-50 W. There was no association between the chamber of the heart and the occurrence of pops. The rate of rise of volumetric temperature (greater than 1.5 °C/s) was the single best predictor of pops (OR: 88.8 [95% CI: 12-604], P < 0.0007). Pops only occurred above a maximum volumetric temperature threshold of 89 °C.
  
  
  CONCLUSIONS
  During irrigated RF ablation, steam pop occurrence can be predicted by both, the rate of rise and the maximum volumetric temperature measured by microwave radiometry.
authors.affiliation: Helmsley Electrophysiology Center, Mount Sinai School of Medicine, New York City, New York, USA.
authors.forename: Jacob S
authors.initials: JS
authors.lastname: Koruth
authors.forename: Srinivas
authors.initials: S
authors.lastname: Dukkipati
authors.forename: Sandeep
authors.initials: S
authors.lastname: Gangireddy
authors.forename: John
authors.initials: J
authors.lastname: McCarthy
authors.forename: Darren
authors.initials: D
authors.lastname: Spencer
authors.forename: Alan D
authors.initials: AD
authors.lastname: Weinberg
authors.forename: Marc A
authors.initials: MA
authors.lastname: Miller
authors.forename: Andre
authors.initials: A
authors.lastname: D'Avila
authors.forename: Vivek Y
authors.initials: VY
authors.lastname: Reddy
mesh_terms: D000818:Animals; D062906:Cardiac Catheters; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D017097:Electric Impedance; D004867:Equipment Design; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000601:surgery*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000601:surgery*; D016015:Logistic Models; D008872:Microwaves; D023421:Models, Animal; D015999:Multivariate Analysis; D016017:Odds Ratio; D011874:Radiometry; D012756:Sheep; D013227:Steam; D013686:Telemetry; D013696:Temperature; D007507:Therapeutic Irrigation / Q000295:instrumentation / Q000379:methods*; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D013227:Steam
keywords: catheter ablation; impedance; microwave radiometry; steam pop; temperature