Predictive value of impedance changes for real-time contact force measurements during catheter ablation of atrial arrhythmias in humans

Target Indices for Clinical Ablation in Atrial Fibrillation

“…This has been described previously in animal studies (using nonirrigated ablation) 2 and recently during clinical ablation in paroxysmal AF and atrial flutter patients, 11 and in another study of almost exclusively paroxysmal AF patients, 12 with both clinical studies using temperature-controlled, power-limited irrigated ablation. The current study and previous work 2,11,12 have demonstrated that for a given ablation duration, the CF during ablation significantly affects the impedance drop. This is not unexpected as greater contact for the same ablation duration would result in more efficient energy delivery to the myocardium, an increase in the tissue temperature and therefore a greater impedance drop.…”

2012 HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Patient Selection, Procedural Techniques, Patient Management and Follow-up, Definitions, Endpoints, and Research Trial Design

“…The surrogate measures of contact used previously, including the fluoroscopic appearance of catheter motion, intracardiac electrogram amplitude, and impedance, have been found to be very poor predictors of CF. 668,670,671,672,674 …”

Deliberate Epicardial Catheter Ablation Lesions

“…In the study by Wong et al, 15 lesion depth increased by ≈1 mm, with each doubling of force in the absence of epicardial fat reaching 7 mm depth in the presence of 70 g of force. This result is difficult to compare directly with previous studies because of the differences in animal models, tissue type, (atrium or ventricle or nonheart tissue), as well as power and duration variations, [9][10][11][12][13][14] but the strength of the relationship is likely to be robust and applicable in humans. This study would have been strengthened…”

“…In endocardial studies, contact force has demonstrated greater correlation with lesion size than other frequently used clinical markers, such as tip temperature, electrogram amplitude, or impedance changes, and has influence on lesion size similar to that of delivered power. [9][10][11][12][13][14] The potential benefit of contact force sensing in the epicardial space has had relatively little attention. In this issue of Circulation: Arrhythmia and Electrophysiology, Wong et al 15 systematically studied the effect of this technology on epicardial tissue, including myocardium (directly on or through fat tissue) and coronary arteries (directly on or adjacent to), and directly on phrenic nerve in an in vivo animal model.…”