Author + information
The QT interval should be corrected for heart rate (HR). Of the formulas proposed for the correction of the QT interval, the one developed by Bazett remains the most used in practice. The popularity of the Bazett formula is based on its simplicity, not on its fit, because the QTc resulting from the Bazett formula is significantly correlated to HR. Based upon theoretical considerations, we have proposed a very simple formula for QT correction : QTc=2QT/((1+RR))
We measured the QT interval in a sample of 758 ECGs, and then we calculate the QTc interval using five methods (Bazett, Fridericia, Hodges, Framingham, and our new formula). To test the appropriateness of the corrections, we correlate the QTc values of each method with HR. An ideal correction should lead to a lack of correlation between QTc and HR. Additionally, because the Bazett formula remains the clinical standard, we used a Bland-Altman analysis to assess the agreement between the Bazett equation and the other methods.
Of the five formulas evaluated, Bazett provides the worst correction (R Bazett = −0.38, R Fridericia = 0.21, R Framingham = 0.22, R Hodges = 0,17, R New = 0,21). The Bland-Altman analysis shows a good agreement between Bazett and the new method (Mean difference 3.8 ms, 95% limits of agreement −5.1 ms to 12.7 ms.), and a bad agreement between Bazett and the other four methods (For Framinham mean difference 14.0 ms, 95% limits −10 to 37.9 ms. For Fridericia mean difference 14.5 ms, 95% limits −8.5 to 37.5 ms. For Hodges mean difference 15.1 ms, 95% limits −7 to 37.1 ms,.)
We propose a simpler, reliable formula for the correction of the QT interval.
Moderated Poster Contributions
Poster Sessions, Expo North
Saturday, March 09, 2013, 3:45 p.m.-4:30 p.m.
Session Title: Arrhythmias: Utililty of ECG for Patients at Risk of SCD
Abstract Category: 6. Arrhythmias: Other
Presentation Number: 1150M-38
- 2013 American College of Cardiology Foundation