Voltage-guided ablation doubles arrhythmia-free survival in the patients who have scar

Design

multicentre randomised clinical trial, 5 Swedish centres, 12-month follow-up (IDEAL-AF)

Population

209 of 936 screened adults having first-time ablation for persistent AF who had low-voltage zones of 3.0 cm2 or more; median age 72 years, 52.2% women

Primary outcome

freedom from documented atrial arrhythmia without antiarrhythmic drugs at 12 months after 1 or 2 procedures

Effect

67.6% vs 37.4%; difference 30.3% (95% CI 17.4-43.2), odds ratio 3.5 (95% CI 2.0-6.2), P<0.001

IDEAL-AF mapped 936 adults having first-time ablation for persistent atrial fibrillation at five Swedish centres and randomised the 209 who turned out to have low-voltage zones of 3.0 cm2 or more. All had pulmonary vein isolation; half then had individualised ablation of those low-voltage zones, half had nothing further. The primary outcome was freedom from documented atrial arrhythmia without antiarrhythmic drugs at 12 months, after one or two procedures within six months.

Arrhythmia-free survival was 67.6% with added low-voltage zone ablation and 37.4% without, an unadjusted difference of 30.3% (95% CI 17.4 to 43.2), odds ratio 3.5 (95% CI 2.0 to 6.2). Time to first recurrence after a single procedure also favoured the strategy, hazard ratio 0.4 (95% CI 0.3 to 0.6). Serious adverse events were similar between groups.

The important number is the one before randomisation: 209 of 936. This is a result about the roughly one patient in four or five with meaningful atrial scar, and it should not be read as a general endorsement of substrate ablation in persistent AF. Trials that ablated substrate without selecting for it have repeatedly failed.

What it changes is the value of the voltage map itself. If mapping is being done anyway, it now carries a decision rather than a description, and a patient found to have 3 cm2 or more of low voltage has a strategy with a large effect available in the same sitting. Where mapping capability or catheter cost is the constraint, this is an argument for spending it on persistent AF rather than on paroxysmal cases.

• Do the voltage map before deciding the strategy, not after, in first-time persistent AF ablation
• Use the trial's own threshold, 3.0 cm2 or more of low voltage, as the trigger for adjunctive ablation
• Tell patients the endpoint was freedom from arrhythmia off antiarrhythmic drugs, which is a stricter bar than most quoted success rates
• Do not extend this to paroxysmal AF or to persistent AF without demonstrated scar
• Budget the extra mapping catheter and procedure time explicitly where the patient is self-funding

The statistics, in plain English

An absolute difference of 30.3 percentage points means about three extra patients stayed in rhythm for every ten treated, which is a large effect by ablation standards; the confidence interval (17.4 to 43.2) keeps the benefit clinically meaningful even at its lower end. The odds ratio of 3.5 sounds larger than the risk difference because odds ratios exaggerate when outcomes are common. The main limitation is selection, not chance: only 22% of screened patients qualified, so the result describes an enriched group and cannot be averaged back across all persistent AF.

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