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Original Articles

Novel Contact Force Sensor Incorporated in Irrigated Radiofrequency Ablation Catheter Predicts Lesion Size and Incidence of Steam Pop and Thrombus

Katsuaki Yokoyama, MD, PhD; Hiroshi Nakagawa, MD, PhD; Dipen C. Shah, MD; Hendrik Lambert, PhD; Giovanni Leo, MS; Nicolas Aeby, MS; Atsushi Ikeda, MD, PhD; Jan V. Pitha, MD, PhD; Tushar Sharma, MD; Ralph Lazzara, MD and Warren M. Jackman, MD

From the Heart Rhythm Institute and Department of Medicine, University of Oklahoma Health Sciences Center (K.Y., H.N., A.I., T.S., R.L., W.M.J.), Department of Pathology, Veterans Administration Medical Center (J.V.P.), Oklahoma City, Oklahoma; Hospital Cantonal De Geneve (D.C.S.) and Endosense SA (H.L., G.L., N.A.), Geneva, Switzerland.

Correspondence to Hiroshi Nakagawa, MD, PhD, Heart Rhythm Institute, University of Oklahoma Health Sciences Center, 1200 Everett Drive (TUH-6E-103), Oklahoma City, Oklahoma 73104. E-mail hiroshi-nakagawa{at}ouhsc.edu

Received July 10, 2008; accepted October 6, 2008.

Background— An open-irrigated radiofrequency (RF) ablation catheter was developed to measure contact force (CF). Three optical fibers measure microdeformation of the catheter tip. The purpose of this study was to (1) validate the accuracy of CF sensor (CFS) (bench test); and (2) determine the relationship between CF and tissue temperatures, lesion size, steam pop, and thrombus during RF ablation using a canine thigh muscle preparation.

Methods and Results— CFS measurements (total 1409) from 2 catheters in 3 angles (perpendicular, parallel, and 45°) were compared with a certified balance (range, 0 to 50 g). CFS measurements correlated highly (R²0.988; mean error, 1.0 g). In 10 anesthetized dogs, a skin cradle over the thigh muscle was superfused with heparinized blood at 37°C. A 7F catheter with 3.5-mm saline-irrigated electrode and CFS (Endosense) was held perpendicular to the muscle at CF of 2, 10, 20, 30, and 40 g. RF was delivered (n=100) for 60 seconds at 30 or 50 W (irrigation 17 or 30 mL/min). Tissue temperature (3 and 7 mm depths), lesion size, thrombus, and steam pop increased significantly with increasing CF at each RF power. Lesion size was greater with applications of lower power (30 W) and greater CF (30 to 40 g) than at high power (50 W) with lower CF (2 to 10 g).

Conclusions— This novel ablation catheter, which accurately measures CF, confirmed CF is a major determinant of RF lesion size. Steam pop and thrombus incidence also increases with CF. CFS in an open-irrigated ablation catheter that may optimize the selection of RF power and application time to maximize lesion formation and reduce the risk of steam pop and thrombus.

Key Words: catheter ablation • fibrillation • tachyarrhythmias • radiofrequency • ventricular tachycardia

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CLINICAL PERSPECTIVE

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