Hazard ratio for progression to AF episode ≥24 h. The figure shows the risk of AF progression to the first episode ≥24 h according to dichotomized ECG parameters, among 418 patients debuted with shorter AF duration. The interatrial block was defined as P-wave duration ≥120 ms combined with biphasic (positive–negative) P-wave in any inferior lead. QTc interval was estimated using the Framingham formula. Hazard ratios were determined in a multivariate Cox model with death as competing risk. Abbreviations: AF, atrial fibrillation; CI, confidence interval; ECG, electrocardiogram; QTc, heart rate-corrected QT interval.