title: The relationship between surface temperature, tissue temperature, microbubble formation, and steam pops.
abstract: BACKGROUND
  It has been proposed that microbubble (MB) monitoring can be used to safely titrate radiofrequency (RF) power. However, MB formation has been found to be an insensitive indicator of tissue temperature during RF delivery. We hypothesized that MB formation corresponds to surface-not tissue--temperature, and therefore would be an insensitive predictor of steam pops.
  
  
  METHODS
  An in vitro bovine heart model was used to measure surface and tissue temperatures during RF delivery under conditions designed to cause steam pops. Sensitivity of type II MB (MBII) formation as a predictor of steam pops and for surface temperatures more than 80 degrees C was calculated.
  
  
  RESULTS
  Of 105 lesions delivered, 99 steam pops occurred. Twenty-one steam pops were preceded by MBII. MBII were seen in 26 lesions, five of which were not associated with steam pop. Surface temperature at onset of MBII was 87 +/- 9 degrees C versus a tissue temperature of 78 +/- 23 degrees C (P = 0.044). Surface temperature at the time of steam pops was 71 +/- 17 degrees C versus a tissue temperature of 102 +/- 17 degrees C (P < 0.0001). The sensitivity of MBII for steam pops was 21%, and 58% for detecting surface temperature in excess of 80 degrees C.
  
  
  CONCLUSIONS
  MBII correlated better with surface temperature than with tissue temperature; steam pops, on the other hand, correlated better with tissue temperature. MBII was an insensitive marker of steam pops and surface temperature in excess of 80 degrees C. Therefore, MBII should not be used to titrate RF power.
authors: Fletcher Allen Health Care/University of Vermont-Cardiology, Mc-Clure 1, Cardiology 111 Colchester Ave, Burlington, VT 05401, USA.
authors: Nathaniel
authors: N
authors: Thompson
authors: Daniel
authors: D
authors: Lustgarten
authors: Bryan
authors: B
authors: Mason
authors: Enkhtuyaa
authors: E
authors: Mueller
authors: James
authors: J
authors: Calame
authors: Stephen
authors: S
authors: Bell
authors: Peter
authors: P
authors: Spector
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology; D002417:Cattle; D005740:Gases / Q000032:analysis*; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000601:surgery*; D007090:Image Interpretation, Computer-Assisted; D045423:Microbubbles; D013227:Steam; D013817:Thermography / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D005740:Gases; D013227:Steam