Target indices for clinical ablation in atrial fibrillation: insights from contact force, electrogram, and biophysical parameter analysis.
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.


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.
Cardiovascular Biomedical Research Unit, St Bartholomew's Hospital, Barts Health NHS Trust, London, United Kingdom.
Waqas
W
Ullah
Ross J
RJ
Hunter
Victoria
V
Baker
Mehul B
MB
Dhinoja
Simon
S
Sporton
Mark J
MJ
Earley
Richard J
RJ
Schilling
D000200:Action Potentials; D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D062906:Cardiac Catheters; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D017097:Electric Impedance; D022062:Electrophysiologic Techniques, Cardiac; D004867:Equipment Design; D005260:Female; D006325:Heart Atria / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008131:London; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013314:Stress, Mechanical; D007507:Therapeutic Irrigation / Q000295:instrumentation; D013997:Time Factors; D016896:Treatment Outcome
atrial electrogram; atrial fibrillation with bradyarrhythmia; catheter ablation