Cut in AF Burden Gains Traction as Gauge of Ablation Success

How much atrial fibrillation (AF) persists after catheter ablation makes a big difference to patients' quality of life (QoL) as well as their need for cardioversion or repeat ablation procedures, suggests a new analysis.

It's the first study tying those outcomes to residual AF burden after ablation achieved using the emerging pulsed-field ablation (PFA) technology, say researchers. These associations are already established for cath ablation using traditional radiofrequency energy or cryoablation.

The new findings come from a secondary analysis of the recently published PULSED-AF study, which highlighted the ablation efficacy of Medtronic's investigational PulseSelect PFA system in patients with either paroxysmal AF (PAF) or persistent AF.

The trial had entered 300 adult candidates for catheter ablation of recurrent, symptomatic PAF or persistent AF at 41 centers in Australia, Canada, Europe, Japan, and the United States.

After ablation, 69% of PAF patients and 62% of those who had persistent AF showed no sign of atrial arrhythmia (AA) over 12 months, based on the trial's method for estimating AA burden.

Residual AA burden less than 10% was seen in 87% and 82% of those initially with PAF and persistent AF, respectively. Burdens in that lowest range, compared with greater AA burden, predicted a "clinically meaningful" improvement in QoL scores in PAF patients.

Those who entered the study with persistent AF showed such improvement — defined as a more than 19-point gain on the AF Effect on Quality-of-Life Questionnaire (AFEQT) — regardless of postablation AA burden.

Moreover, patients initially with either type of AF and residual burdens in the lowest range went on to have fewer cardioversions and repeat ablations (P < .01), reported Atul Verma, MD, McGill University Health Centre, Montreal, Canada, May 19 at the Heart Rhythm Society (HRS) 2023 Scientific Sessions, held in New Orleans, Louisiana.

Verma, the trial's principal investigator, is also lead author on the same-day publication of the secondary analysis in Heart Rhythm.

Binary Endpoint Lacks Relevance

The PULSED-AF primary analysis defined ablation efficacy partly as freedom from AA recurrence lasting at least 30 seconds, with or without symptoms, a traditional AF-ablation trial endpoint that is nonetheless considered clinically unhelpful.

The secondary analysis recasts that binary endpoint as degree of reduction in AF burden, a continuous variable. That potentially allows AF ablation efficacy to be assessed in a more nuanced way likely to be more meaningful to patients and the healthcare system, observe Verma and colleagues.

The "30-second endpoint" is limited in clinical usefulness and "doesn't mean much to the patient," he said at a press conference on the analysis before formally presenting it at the HRS sessions.

Recent AF ablation trials have explored AA burden as possibly a superior way to assess the procedure's success "but also to see if it's better correlated with quality of life and healthcare outcomes," Verma said. "So that's exactly what we've tried to do here using the PULSED-AF data."

In the secondary analysis, he said, patients' rate of freedom from the 30-second endpoint was about 70%, but "more than 85% of them had an AF burden of less than 10%."

"This efficacy endpoint of 30 seconds of atrial arrhythmia has been challenged and has been seen clinically as insignificant," agreed Rajeev Pathak, MBBS, PhD, of Australian National University and director of cardiac electrophysiology at Canberra Hospital, Australia.

In AF radiofrequency ablation and cryoablation studies "there is clear disconnect between these 30-second episodes of atrial arrhythmias we see and the clinical relevance of healthcare utilization and quality of life," said Pathak, invited discussant for Verma's presentation at the sessions.

Now an AF ablation trial using PFA catheters has yielded similar results, finding AA burden to be "a more objective and relevant measure of success," he said. "A 30-second endpoint is arbitrary, lacks significance, and is highly dependent on the monitoring strategy."

The More You Look, the More You See

The new secondary analysis included a demonstration that success rates based on the 30-second endpoint indeed vary depending on how subsequent arrhythmias are monitored.

As described by Verma, PULSED-AF data were assessed for the 30-second endpoint captured using three separate intermittent monitoring strategies that it and other recent ablation trials have used:

Strategy A: Transtelephonic monitoring weekly and in the event of symptoms, plus 24-hour Holter monitoring at 6 and 12 months and 12-lead ECG at 3, 6, and 12 months
Strategy B: Transtelephonic monitoring weekly and at symptoms for 3 to 6 months followed by monthly and at symptoms from 6 to 12 months, plus 24-hour Holter monitoring at 6 and 12 months, plus 12-lead ECG at 3, 6, and 12 months
Strategy C: The median of two 24-hour Holter monitoring sessions per patient over 12 months

As Verma reported, rates of freedom from the 30-second endpoint climbed with successive monitoring strategies. The rates for PAF and persistent-AF patients, respectively, were:

Strategy A: 70% and 62%
Strategy B: 71% and 68%
Strategy C: 91% and 86%

"If you're using the 'freedom-from-30-seconds' endpoint, the results that you are going to get are highly dependent on the monitoring strategy," Verma said. "The more you look, the more you see."

Valid Estimation of Burden

For the main PULSED-AF secondary analysis, the investigators defined AA burden according to findings on either Holter monitoring or the 12-lead ECG. "So as not to bias these results," Verma said, "for every patient, we picked the method that gave us the highest atrial arrhythmia burden."

Ideally, Verma explained to the theheart.org | Medscape Cardiology, arrhythmia burden would be determined using devices such as implantable loop recorders. "The problem is, this is expensive and not practical" in both clinical practice and many trials, so PULSED-AF investigators went with the intermittent monitoring strategy to estimate burdens.

Their method appears valid, he said, given that the study identified a statistically relevant 10% AA burden cut off for predicting QoL improvement or less healthcare resource use.

"If their residual atrial arrhythmia burden was greater than 10%, they did not have a statistically significant improvement in quality of life," Verma observed. And "very few" of them had cardioversions or repeat ablation.

"I couldn't agree more" that residual AA burden is preferable to the 30-second endpoint for gauging AF ablation success, Kenneth Ellenbogen, MD, Virginia Commonwealth University Medical Center, Richmond, told theheart.org | Medscape Cardiology. Ellenbogen is director of clinical cardiac electrophysiology and pacing at Pauley Heart Center and not associated with PULSED-AF.

That AA burden was linked to healthcare resource use in the study "is absolutely brilliant," he said, "because that's what the bean counters really want at the end of the day. And as doctors we care about patients feeling better — improving quality of life."

PULSED-AF was funded by Medtronic. Verma disclosed honoraria or fees for speaking or consulting from Bayer Healthcare Pharmaceuticals, Biosense Webster, Medtronic, Thermedical, Kardium, and Galaxy Medical; and research grants from Adagio Medical. Ellenbogen disclosed honoraria or fees for speaking or consulting from Boston Scientific, Medtronic, Kestra, Hylomorph, Biotronik, MediLynx, Impulse Dynamics USA, Abbott, Biosense Webster, Milestone Pharmaceuticals, Sanofi, and Medpace; and royalties from Elsevier. Pathak has disclosed no relevant financial relationships.

Heart Rhythm Society (HRS) 2023 Scientific Sessions: Abstract LB-456089-4. Presented May 19, 2023.

Heart Rhythm. Published online May 19, 2023. Full Text

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