Target Indices for Clinical Ablation in Atrial Fibrillation

Abstract

Background-In animal studies of radiofrequency ablation, lesion sizes plateau as the maximum lesion size is reached for an ablation. Lesion parameters are not available in clinical ablations, but preclinical work suggests that these correlate with impedance drop and electrogram attenuation. Characterization of the relationships between catheter contact force, ablation duration, and these surrogate markers of lesion formation may allow us to define targets for effective ablation. Methods and Results-Fifteen patients undergoing first-time radiofrequency ablation for nonparoxysmal atrial fibrillation were studied. All were in atrial fibrillation at the time of the procedure. Ablations were performed with an irrigated-tip contact force-sensing catheter in temperature-controlled mode (temperature limited to 48°C, power to 30 W). Included were 285 left atrial static ablations, 247 with additional impedance data. The ablation force time integral (FTI) correlated with the attenuation of the electrogram with ablation (Spearman ρ, -0.14; P=0.02): the relationship plateauing from 500 g·s, a reduction in the electrogram amplitude of 20%. The FTI also correlated with the impedance drop during ablation (Spearman ρ, 0.79; P<0.0005): the relationship was logarithmic, the reduction in the impedance with an increasing FTI also plateauing from 500 g·s, an impedance drop of 7.5%. The ablation duration affected the impedance drop at an FTI if the duration was <10 s. Beyond this time point, the FTI achieved rather than the ablation duration or mean contact force applied determined the impedance drop. Conclusions-During nonparoxysmal atrial fibrillation ablation, an FTI of 500 g·s should be targeted with ablation duration of ≥10 s. Clinical Trials Registration-URL: http://clinicaltrials.gov/. Unique Identifier: NCT01587404.(Circ Arrhythm Electrophysiol. 2014;7:63-68.)

A Comparison of Remote Magnetic Irrigated Tip Ablation versus Manual Catheter Irrigated Tip Catheter Ablation With and Without Force Sensing Feedback

“…[4][5][6][7][8] When applied in prospective clinical study designs, catheters that provide feedback of tip-tissue contact force to the operator appear to improve outcomes. 8,9 Current RMN catheters do not have direct force-sensing feedback.…”

Impact of Catheter Contact Force on Human Left Atrial Electrogram Characteristics in Sinus Rhythm and Atrial Fibrillation

“…6 Electrogram complex size was measured from the dominant peak to trough of a complex using previously described methods, 14 and averaged for the signal, Figure 1. Complexes <0.05 mV (peak to trough) were assigned as noise.…”

“…One thousand nine hundred forty-five data points were collected (1396 in AF, 549 in SR, and 59 [37-107] per patient at 19 [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] locations), and the spread of CFs is shown in Figure 2B.…”

Contact Force–Sensing Catheters

“…In this edition of Circulation: Arrhythmia and Electrophysiology, Ullah et al 7 perform a detailed analysis of the relationship between impedance changes, electrogram amplitude, and contact force in 15 patients undergoing catheter ablation of persistent AF; the majority used the Hanson robotic system. An irrigated contact force-sensing catheter (SmartTouch, Biosense Webster, Inc, Diamond Bar, CA) was used with a maximum power delivery of 30 W and irrigation flow rate of 17 mL/min.…”

“…Whether the addition of contact force sensing will allow us to achieve the elusive goal of persistent PV isolation with a focal ablation catheter remains to be seen. The analysis from Ullah et al 7 has given us the tools to help answer this question. …”