Efficacy of a cooled bipolar epicardial radiofrequency ablation probe for creating transmural myocardial lesions.
OBJECTIVE
Creation of transmural myocardial lesions with epicardial surgical devices to treat atrial fibrillation is difficult. A new cooled bipolar radiofrequency ablation probe was used to create transmural myocardial lesions under controlled conditions.


METHODS
The Coolrail (AtriCure, Inc, West Chester, Ohio) is a handheld probe with 2 parallel 30-mm long radiofrequency conductors. Conductors are cooled by water irrigation. Lesions were delivered to epicardial surface of isolated bovine myocardium sliced 3- to 8-mm thick, with blood flow beneath tissue at 0 or 0.4 m/s. Contact pressure between probe and tissue was either 450 g or 900 g. Tissue temperatures were measured. Tissue was sectioned every 5 mm along lesion long axis to determine lesion dimensions.


RESULTS
For 80 experiments with 450-g contact pressure, epicardial lesion length was 31.3 mm (interquartile range, 30.1-32.8 mm); endocardial lesion length was 14.1 mm (interquartile range, 0.0-22.6 mm). Average lesion depth was 4.2 +/- 0.74 mm. Temperature at probe interface was 81 degrees C +/- 21 degrees C; that at blood pool interface was 53 degrees C +/- 12 degrees C. Lesions were always transmural when tissue thickness was 4.0 mm or less. Endocardial blood flow did not influence lesion depth. With 900-g contact pressure, increased depth was always transmural at 4.8-mm tissue thickness or less.


CONCLUSIONS
This irrigated bipolar radiofrequency probe consistently produced transmural lesions in tissue 4 mm or thinner under controlled conditions in vitro. Lesion depth was increased by greater pressure on probe and not affected by blood flow. Endocardial lesions were smaller than epicardial dimensions.
Wood
Mark A
MA
Division of Cardiac Electrophysiology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0053, USA. mwoodmd@pol.net
Ellenbogen
Amy L
AL
Pathak
Vishesh
V
Ellenbogen
Kenneth A
KA
Kasarajan
Vigneshwar
V
D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation*; D002417:Cattle; D003080:Cold Temperature; D022062:Electrophysiologic Techniques, Cardiac / Q000295:instrumentation; D004867:Equipment Design; D066298:In Vitro Techniques; D023421:Models, Animal; D008955:Models, Cardiovascular; D009206:Myocardium / Q000473:pathology; D012756:Sheep