Design: multicentre randomised clinical trial, 12 months' follow-up, 5 Swedish centres
Population: 209 adults with persistent atrial fibrillation and low-voltage zones ≥3.0 cm², from 936 screened
Primary outcome: freedom from 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 (2.0–6.2)

IDEAL-AF screened 936 adults having first-time ablation with voltage mapping for persistent atrial fibrillation across five Swedish centres, and randomised the 209 who had low-voltage zones of 3.0 cm² or more. After pulmonary vein isolation, 102 received individualised adjunctive low-voltage zone ablation and 107 received nothing further. Median age was 72 and 52.2% were women.

Freedom from documented atrial arrhythmia without antiarrhythmic drugs at 12 months, after one or two procedures within six months, was reached by 67.6% with adjunctive ablation against 37.4% with isolation alone — an unadjusted difference of 30.3% (95% CI 17.4 to 43.2), odds ratio 3.5 (2.0 to 6.2), P < 0.001. Time to first recurrence after a single procedure also favoured the strategy (HR 0.4, 0.3 to 0.6). Quality of life improved more, and serious adverse events were similar.

The selection step is what makes this usable. Only 209 of 936 screened patients — just over a fifth — had enough low-voltage substrate to enter, so this is not an argument for adding substrate ablation to every persistent case. It is an argument for mapping, and then acting on what the map shows.

Perform voltage mapping in persistent atrial fibrillation before deciding the ablation set
Reserve adjunctive low-voltage ablation for patients who actually have a substantial low-voltage zone
Counsel that the comparison was against isolation alone, not against a different substrate strategy
Record procedure time and complications locally — safety here was similar but the operators were experienced

Why it matters

It gives voltage mapping a decision to drive rather than a description to record.

The statistics, in plain English

An absolute difference of 30.3 percentage points is large, and a confidence interval of 17.4 to 43.2 keeps it large even at its lower bound. With 209 patients the interval is wide, so the precise size is uncertain even though the direction is not. The trial randomised only the fifth of screened patients with substantial low-voltage substrate, so the result applies to that group and not to persistent atrial fibrillation generally.