title: Electrode impedance: an indicator of electrode-tissue contact and lesion dimensions during linear ablation.
abstract: Pre-ablation impedance was evaluated for its ability to detect electrode-tissue contact and allow creation of long uniform linear lesions with a multi-electrode ablation catheter. The study consisted of 2 parts, both of which used the in vivopig thigh muscle model. In part 1, a 7 Fr. multi-electrode catheter was held in 3 electrode-tissue contact conditions: (1) non-contact; (2) light contact with a 30g downward force; and (3) tight contact with a 90g downward force. Impedances were measured in unipolar, modified unipolar and bipolar configurations using a source with frequencies from 100Hz to 500kHz. Compared with non-contact, the impedance increased 35 +/- 22 % with 30g contact pressure and 68 +/- 40% when the contact pressure was increased to 90g across the range of frequencies studied. In part 2, the same catheter was held against the tissue with different forces. Pre-ablation impedance was measured using a 10kHz current. Phased radiofrequency energy was applied to the 5 electrodes simultaneously using 10W power at each electrode for 120s. A total of 32 linear lesions were created. The lesion dimensions correlated with pre-ablation impedance. A unipolar impedance > or = 190 Omega indicates 95% possibility to create a uniform linear lesion of at least 3mm depth with our ablation system. We conclude that pre-ablation impedance may be a useful indicator for predicting electrode-tissue contact and the ability to create a continuous and transmural linear lesion with a multi-electrode catheter.
authors.affiliation: Cardiac Rhythm Management Laboratory, Division of Cardiovascular Diseases, Department of Medicine, University of Alabama at Birmingham, AL 35294, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zheng
authors.forename: G P
authors.initials: GP
authors.lastname: Walcott
authors.forename: J A
authors.initials: JA
authors.lastname: Hall
authors.forename: D L
authors.initials: DL
authors.lastname: Rollins
authors.forename: W M
authors.initials: WM
authors.lastname: Smith
authors.forename: G N
authors.initials: GN
authors.lastname: Kay
authors.forename: R E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D017097:Electric Impedance; D004566:Electrodes; D023421:Models, Animal; D018482:Muscle, Skeletal / Q000503:physiopathology; D011336:Probability; D012680:Sensitivity and Specificity; D013552:Swine