title: Counter intuitive relations between in vivo RF lesion size, power, and tip temperature.
abstract: BACKGROUND
  Radiofrequency (RF) lesion size in vitro is positively correlated with applied power and catheter tip temperature. However, the relation between RF lesion size, power, and tip temperature in vivo remains unclear. We hypothesized that due to flow, anatomy and tip contact effects in vivo, increased tip temperature would be inversely related to applied power and RF lesion size.
  
  
  METHODS
  RF lesions were created on the endocardium of 16 pigs using 5, 6, and 7 Fr catheters. The ablation generator was set to achieve a temperature of 70 degrees C. RF lesions were created in different regions of the heart so as to encompass a wide range of blood flow and catheter movement conditions. RF lesions were measured acutely (DIMEN, mm) and correlated with average power applied (POWER, W), and average tip temperature (TEMP, degrees C). The POWER and TEMP relation was also examined.
  
  
  RESULTS
  For TEMPs below 55 degrees C, the power output from the generator was typically maximized at 50 W. At TEMPs above 55 degrees C, POWER decreased exponentially with increasing TEMP (POWER = 50 - exp(-((41-TEMP)/7)), r = 0.98, p < 0.05). Further, DIMEN tended to be inversely related to TEMP (Slope: -0.07 +/- 0.04, r = -0.15, p = 0.07); but, was positively related to POWER (Slope: 0.04 +/- 0.02, r = 0.23, p < 0.05). These relations varied by tip size and estimated local blood flow characteristics.
  
  
  CONCLUSIONS
  In vivo, variable tissue contact and flow yield DIMEN-POWER-TEMP relations opposite to those found in vitro. These counterintuitive results suggest that maximum in vivo RF lesion size is achieved when power is maximized at tip temperatures between 50 and 60 degrees C.
authors: Department of Pediatrics, Medical University of South Carolina, Charleston, SC 29425, USA. mukherr@musc.edu
authors: Rupak
authors: R
authors: Mukherjee
authors: Preecha
authors: P
authors: Laohakunakorn
authors: M Charles
authors: MC
authors: Welzig
authors: Kathryn S
authors: KS
authors: Cowart
authors: J Philip
authors: JP
authors: Saul
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D004699:Endocardium / Q000601:surgery; D013552:Swine; D013696:Temperature