Effect of saline irrigation flow rate on temperature profile during cooled radiofrequency ablation
Introduction: Cooled radiofrequency ablation has been developed clinically for the treatment of ventricular tachycardia. Although clinical studies employ a constant saline flow rate for cooling, we hypothesized that varying the flow rates might optimize the temperature profile at depth.Methods: In excised ovine left ventricle, we compared the temperature profile from a catheter tip electrode thermocouple to those placed at depths of 0.0 mm, 1.0 mm, and 2.0 mm. We compared the following settings: 20 Watts without flow, 20 Watts with 0.3 cc/sec flow, 20 Watts with 0.5 cc/sec flow, and 70 degrees C surface temperature without flow (temperature control).Results: The temperatures decreased from 77.5+/-10.5 degrees C, 91.7+/-6.3 degrees C, 65.5+/-11.8 degrees C, and 52. 5+/-11.8 degrees C at 20 W without saline irrigation at the tip, 0.0 mm, 1.0 mm, and 2.0 mm, respectively, to 33.0+/-1.4 degrees C*, 63. 4+/-7.0 degrees C*, 57.1+/-5.8 degrees C*, 49.9+/-5.8 degrees C+ at 20 W with 0.5 ml/sec flow (*P<0.01, +P=0.09). The lesion volumes were 79.6 mm(3) for 20 W without flow, 64.1 mm(3) for 20 W with 0.3 ml/sec flow, 47.5 mm(3) for 20 W with 0.5 ml/sec flow, and 28.6 mm(3) for temperature control.Conclusions: We conclude that 1) the temperature profile greatly depends upon the rate of saline flow for cooling; 2) at high flow rates, the 0.0 mm and 1.0 mm temperatures are similar; 3) even at high irrigation rates, lesion size is greater than for temperature control; 4) the tip temperature significantly underestimates the surface temperature and improved methods of measuring temperature are needed.
Wong
WS
Cardiac Arrhythmia Service, New England Medical Center, Boston, MA.
VanderBrink
BA
Riley
RE
Pomeranz
M
Link
MS
Homoud
MK
Estes
III
Wang
PJ