SmartTouch Contact-Force Sensing Data Fail to Fire in Atrial-Fibrillation Ablation

Patrice Wendling

May 13, 2016

SAN FRANCISCO, CA — Switching on the SmartTouch (Biosense Webster) catheter's real-time contact-force (CF) sensing data reduced acute reconnection rates during paroxysmal atrial fibrillation (AF) ablation but had no significant effect on long-term success, procedure or fluoroscopy times, or complication rates in a head-to-head comparison by the UK Multicentre Trials Group[1].

"The take-home message from this trial is that while real-time contact-force sensing data clearly let us know how hard we are pressing, this alone does not improve ablation outcomes: to do this we need to know how hard to press and even how to press," study author Dr Waqas Ullah (St Bartholomew's Hospital, London, UK) told heartwire from Medscape.

The data were reported at the Heart Rhythm Society (HRS) 2016 Scientific Sessions and published online in Heart Rhythm.

Session comoderator Dr John Day (Intermountain Healthcare, Salt Lake City, UT) remarked to heartwire that the late-breaking clinical-trial session was filled with negative AF trials—be it using rotor mapping, left atrial appendage excision, or CF-sensing data, once heralded as the latest, greatest thing in ablation.

"I think this highlights a bigger issue: that we still haven't got it figured out how best to treat persistent atrial fibrillation," he said.

Prior work reported earlier in the learning curve for CF-sensing technology showed higher success rates and shorter procedure and fluoroscopy times.

The UK study, however, used the same equipment in both arms (catheter, navigation system, ablation power, and irrigation settings) and included more experienced operators, with most having performed over 30 SmartTouch cases, Ullah said.

Another important factor is that extensive investigation for pulmonary vein (PV) reconnection was undertaken at 60 minutes and reablation performed if veins remained isolated. "This may have served to minimize the difference between the two groups in the long term because any suboptimal ablation in the contact-force–blinded group may have been corrected by this reisolation," he said.

At 1 year, 49% of patients in the CF-on arm and 52% in the CF-off arm were free of symptomatic or asymptomatic AF or atrial tachycardia without antiarrhythmic drugs (P=0.7).

Switch On, Switch Off

The study randomly assigned 120 patients undergoing first-time persistent-AF ablation at seven UK centers to ablation with or without CF data displayed to the operator. The study's primary hypothesis was that CF data would shorten the time needed for PV isolation (PVI), but there were no significant differences between the CF-off and CF-on arms for total PVI time (73 min vs 70 min; P=0.82), total fluoroscopy time (830 s vs 648 s; P=0.82), or total procedure time (196 min vs 194 min; P=0.96).

"When contact-force data were available, operators seemed more confident or happy to keep their foot to the pedal, so each application was significantly longer (mean 52.3 s vs 43.2 s; P<0.0005)," Ullah added.

Use of CF data was also associated with a significant 31% reduction in acute PV reconnection rates at 1 hour (P=0.03) and fewer CF readings outside the broad 5g–40g-pressure target range (20% vs 32%; P<0.001), indicating improved CF control, Ullah said.

Despite this, there was no difference between the CF-off and CF-on arms in major complications (three vs two) or minor ones (two vs four).

Ullah suggested that the next step is to use different CF parameters such as force time integral (FTI) and ablation index (AI) as well as automated lesion marking software such as Visitag (Biosense Webster). FTI incorporates ablation duration and time; AI additionally includes ablation power.

"Certainly in most of our participating institutions, the use of these parameters has become the standard of care for ablation procedures, with the aim of ensuring that every radiofrequency application is optimized in terms of efficacy and safety," he told heartwire .

The study was funded by an investigator-initiated study grant from Biosense Webster, with support from the National Institute for Health Cardiovascular Biomedical Research Unit at Barts Health NHS Trust. Ullah reported no relevant financial relationships. Disclosures for the coauthors are listed in the abstract.

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