Measurement of electrical coupling between cardiac ablation catheters and tissue.

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.

Use of electrical coupling information in AF catheter ablation: a prospective randomized pilot study.

BACKGROUND: Catheter contact is important for radiofrequency (RF) ablation. Local electrical catheter-to-tissue coupling has been described as a tool to objectively measure contact. OBJECTIVE: We hypothesized that pulmonary vein isolation (PVI) ablation using electrical coupling information (ECI) would yield higher rates of PVI than an approach without ECI. METHODS: Forty patients with atrial fibrillation were prospectively included. In each patient, 1 pair of pulmonary veins (PVs) was randomly chosen to be encircled with ECI available while the other pair was encircled without use of ECI. RESULTS: The rate of PVI was significantly higher in PVs encircled with ECI available (58% vs 30%; P = .024). PV encircling with coupling resulted in slightly longer procedure (26.5 [interquartile range {IQR} 22-32.5] vs 23.5 [IQR 19-26.5] minutes; P = .019), fluoroscopy (9.0 [IQR 6-12] vs 6.9 [IQR 4-8.6] minutes; P = .011), and RF (20.0 [IQR 16.5-23.5] vs 17.3 [IQR 15.1-20.6] minutes; P = .015) times. For nonisolated PVs, the coupling group had significantly fewer gaps (3.0 [IQR 1.8-7] vs 6.0 [IQR 4-11]; P = 0.021) and gap mapping/closure needed shorter procedure (9.0 [IQR 4-16] vs 13.0 [IQR 11-21] minutes; P = .04), fluoroscopy (3.9 [IQR 2-7.1] vs 6.0 [IQR 4.6-7.9] minutes; P = .038), and RF (1.9 [IQR 0.9-5] vs 5.2 [IQR 3.3-8.6] minutes; P = .016) times. CONCLUSIONS: The use of ECI improved lesion deployment measured as higher rates of PVI after anatomical encircling. For nonisolated PVs, fewer gaps and faster gap closure were found using ECI.

First in human validation of impedance-based catheter tip-to-tissue contact assessment in the left atrium.

BACKGROUND: In this study, a new method of contact assessment based on the measurement of the local electrical properties at the catheter tip-to-tissue interface was validated in a blinded fashion in vivo in the human left atrium. METHODS: Using a 3-terminal circuit model, local resistance and reactance between catheter tip and tissue surface were measured and combined in an electrical coupling index (ECI). Twelve patients undergoing atrial fibrillation (AF) catheter ablation were included in this study. The catheter was placed in the left atrium at various levels of contact. Blinded to the physician, measurements of electrogram amplitudes, pacing thresholds, and impedances at the catheter tip-to-tissue interface were performed. RESULTS: As the catheter went from noncontact to contact, ECI increased from 118 +/- 15 to 145 +/- 24 (P < 0.0001), electrogram amplitudes increased from 0.14 +/- 0.16 to 2.0 +/- 1.9 mV (P < 0.0001), and pacing thresholds decreased from 13.9 +/- 3.1 to 3.1 +/- 2.0 mA (P < 0.0001). ECI was significantly higher in vascular tissue as compared with trabeculated and smooth myocardium. Patch orientation, operator, body mass index, or clinical type of AF had no influence on ECI values. On a patient-by-patient analysis, true contact/noncontact locations showed a mean ECI difference of 32.7 +/- 11.6 units (95% CI 25.8-39.6). A cut-off value of 5 ECI units was able to separate contact from noncontact with 97% sensitivity and 95% specificity. CONCLUSION: Measurement of local impedances between catheter tip and tissue is feasible to reproducibly describe electrical catheter contact within the left atrium in a clinical setting of AF catheter ablation.

Real-time monitoring of luminal esophageal temperature during left atrial radiofrequency catheter ablation for atrial fibrillation: observations about esophageal heating during ablation at the pulmonary vein ostia and posterior left atrium.

INTRODUCTION: Left atrial radiofrequency catheter ablation (RFA) is gaining acceptance as treatment for drug-refractory atrial fibrillation (AF). This therapy has been associated with esophageal injury and atrioesophageal fistula formation causing death. METHODS: We describe 3 patients undergoing catheter ablation for AF during real-time monitoring of luminal esophageal temperature. RESULTS: We observed heating of the esophagus during short duration low power RFA, at either the left or right pulmonary vein ostia. Cryoablation at the pulmonary vein ostium in one patient resulted in esophageal cooling. Furthermore, we observed that fluoroscopic localization of the ablation catheter at a site apparently distant from the esophagus is not adequate to assure avoidance of ablation-induced esophageal heating. CONCLUSIONS: Real-time monitoring of luminal esophageal position and temperature is feasible, enhances recognition of esophageal heating, and may add useful information beyond that provided by fluoroscopic assessment of esophageal position. There is a potential role for esophageal monitoring to help avoid thermal injury to the esophagus during catheter ablation for atrial fibrillation.