Measurement of Electrical Coupling Between Cardiac Ablation Catheters and Tissue

Abstract

Managing cardiac arrhythmias with catheter ablation requires positioning electrodes in contact with myocardial tissue. Objective measures to assess contact and effective coupling of ablation energy are sought. An electrical coupling index (ECI) was devised using complex impedance at 20 kHz to perform in the presence of RF ablation and deliver information about electrical interactions between the tip electrode and its adjacent environment. ECI was derived and compared with clinical judgment, pacing threshold, electrogram amplitude, and ablation lesion depth and transmurality in a porcine model. ECI was also compared with force and displacement using ex vivo bovine myocardial muscle. Mean noncontact ECI was 97.2 ± 14.3 and increased to 145.2 ± 33.6 (p <; 0.001) in clinician assessed (CLIN) moderate contact. ECI significantly improved CLIN's prediction of the variance in pacing threshold from 48.7% to 56.8% ( ). ECI was indicative of contact force under conditions of smooth myocardium. Transmural lesions were associated with higher pre-RF (109 ± 17 versus 149 ± 25, ) and during-RF (82 ± 9 versus 101 ± 17, ) ECI levels. ECI is a tip specific, robust, correlate with contact and ablation efficacy, and can potentially add to clinical interpretation of electrical coupling during electrophysiology procedures.

Multicentre randomised trial comparing contact force with electrical coupling index in atrial flutter ablation (VERISMART trial)

“…As such, it is a direct measurement of CF but provides no information on tissue viability. The Ensite Verisense (St Jude Medical, St Paul MN, US), does not measure contact force, but provides data on the tissue catheter interaction using a proprietary algorithm based on the resistance and reactance of the underlying tissue [4,12]. The ECI therefore reflects a composite of contact (but not quantitatively as in the case of CF) and tissue viability.…”

Development of a clinically relevant ex vivo model of cardiac ablation for testing of ablation catheters

“…A variety of ex vivo cardiac ablation models have been reported, each having advantages and disadvantages 10–21 . Ex vivo cardiac ablation models can be subdivided into three categories: models using skeletal canine muscle, 10 models using cardiac tissue, 13–21 and models using nonviable tissues and tissue phantoms 11,12 .…”

Introducing a novel catheter–tissue contact feedback feature in robotic navigated catheter ablation: Utility, feasibility, and safety

“…Numerous studies have been conducted in search of the best indicator of catheter–tissue contact. 1 , 2 , 3 , 4 , 5 , 6 , 7 Impedance measurements have been proposed, but these measurements alone have always been regarded as surrogate measures. 7 The contact quest came to its highpoint with the development of CF sensing catheters for manual-guided RF CA procedures.…”

“… 1 , 2 A variety of measures can be used to estimate the degree of contact, such as tactile feedback, catheter positioning on fluoroscopic and ultrasound imaging, catheter manipulation history, baseline impedance, impedance change, electrocardiogram amplitude assessment, and electrode temperature. 1 , 3 , 4 In addition, complex electrical impedance and the associated electric coupling index have been used to assess contact 4 , 5 and lesion size. 6 However, all of these measures are still regarded as surrogate markers of effective lesion formation.…”