Contact sensing provides a highly accurate means to titrate radiofrequency ablation lesion depth.

BACKGROUND: Transmural lesions are essential for efficacious ablation. There are, however, no accurate means to estimate lesion depth. OBJECTIVE: Explore use of the electrical coupling index (ECI) from the EnSite Contact™ System as a potential variable for lesion depth estimation. METHODS: Radiofrequency (RF) ablation lesions were created in atria and the thighs of swine using an irrigated RF catheter. Power was 30 W for 20 or 30 seconds intracardiac and 30-50 W for 10-60 seconds for the thigh. Intracardiac, the percentage change in ECI during ablation was compared with transmurality and collateral damage occurrence. For the thigh model, an algorithm estimating lesion depth was derived. Factors included: power, duration, and change in the ECI subcomponents (ΔECI+) during ablation. The ΔECI+ algorithm was compared to one using power and duration (PD) alone. RESULTS: Intracardiac, lesions with ≥12% reduction in ECI were more likely to be transmural (92.3% vs. 59.4%, P < 0.001). Twenty-second lesions were less likely to cause collateral damage compared to 30 seconds (33% vs. 70%, P = 0.003), while transmurality was similar. With the thigh model, ΔECI+ had a better correlation than the PD algorithm (P < 0.01). Accuracy of the ΔECI+ algorithm was unimproved with inclusion of tip orientation, while PD improved (R(2) = 0.64). DISCUSSION: Change in ECI provides evidence of transmural versus nontransmural swine intracardiac atrial lesions. A lesion depth estimation algorithm using ECI subcomponents is unaffected by tip orientation and is more accurate than using PD alone. CONCLUSION: Use of ECI as a factor in a lesion depth algorithm may provide clinically valuable information regarding the efficacy of intracardiac RF ablation lesions.

Electroanatomic mapping of the left ventricle in a porcine model of chronic myocardial infarction with magnetic resonance-based catheter tracking.

BACKGROUND: X-ray fluoroscopy constitutes the fundamental imaging modality for catheter visualization during interventional electrophysiology procedures. The minimal tissue discriminative capability of fluoroscopy is mitigated in part by the use of electroanatomic mapping systems and enhanced by the integration of preacquired 3-dimensional imaging of the heart with computed tomographic or magnetic resonance (MR) imaging. A more ideal paradigm might be to use intraprocedural MR imaging to directly image and guide catheter mapping procedures. METHODS AND RESULTS: An MR imaging-based electroanatomic mapping system was designed to assess the feasibility of navigating catheters to the left ventricle in vivo using MR tracking of microcoils incorporated into the catheters, measuring intracardiac ventricular electrograms, and integrating this information with 3-dimensional MR angiography and myocardial delayed enhancement images to allow ventricular substrate mapping. In all animals (4 normal, and 10 chronically infarcted swine), after transseptal puncture under fluoroscopic guidance, catheters were successfully navigated to the left ventricle with MR tracking (13 to 15 frames per second) by both transseptal and retrograde aortic approaches. Electrogram artifacts related to the MR imaging gradient pulses were successfully removed with analog and digital signal processing. In all animals, it was possible to map the entire left ventricle and to project electrogram voltage amplitude maps to identify the scarred myocardium. CONCLUSIONS: It is possible to use MR tracking to navigate catheters to the left ventricle, to measure electrogram activity, and to render accurate 3-dimensional voltage maps in a porcine model of chronic myocardial infarction, completely in the MR imaging environment. Myocardial delayed enhancement guidance provided dense sampling of the proximity of the infarct and accurate localization of complex infarcts.