Material and Method: This retrospective study included the AF patients treated at Central Chest Institute of Thailand. The corrected QT intervals (QTc) during AF and sinus rhythm (SR) were calculated by using the Fridericia formula, Van de Water formula, and Hodges formula. A paired Student’s t-test was used to compare the average QTc in AF and SR in each formula.

Results: Eighty-eight patients were enrolled. Most patients were paroxysmal AF. Comparing with SR, Hodges formula overestimated the QTc during AF with rapid response, while Fridericia formula and Van de Water formula underestimated the QTc. The QTc calculated by using Fridericia formula was less dependent on heart rate (r = 0.20, p = 0.07) than Hodges formula (r = -0.51, p<0.01) and Van de Water formula (r = 0.61, p<0.01). The Hodges formula was less dependent on heart rate (r = -0.24, p = 0.29) in 21 patients with heart rate in AF or SR between 60 to 100 beats/minute. However, there was no significant difference between QTc in AF and SR calculated by using Hodges formula (p = 0.86).

Conclusion: Although the QTc during AF and SR, calculated by using Hodges formula, was nearly the same, but the Fridericia formula was the least dependent on heart rate. The Hodges formula is the optimal QT correction method in AF patients without tachycardia or bradycardia.

Keywords: Atrial fibrillation, Corrected QT interval, Fridericia formula, Van de Water formula, Hodges formula