Rate-corrected QT interval: Techniques and limitations

doi:10.1016/0002-9149(93)90035-B

The American Journal of Cardiology

Volume 72, Issue 6, 26 August 1993, Pages B17-B22

https://doi.org/10.1016/0002-9149(93)90035-B Get rights and content

Abstract

The duration of the QT interval on the surface electrocardiogram represents the time required for all ventricular depolarization and repolarization processes to occur. Among the many physiologic and pathologic factors that contribute to the QT interval, heart rate plays a major role. Several approaches have been used to correct the QT interval, all of which take into account the heart rate at which the interval is measured. The simplest and most common approach to correcting the QT interval is to divide its value by the square root of the preceding RR interval expressed in seconds, i.e., by using Bazett's formula. This calculation provides a corrected QT (QT_c) interval that represents the QT interval normalized for a heart rate of 60 beats/min. However, several studies have shown that Bazett's correction formula is not optimal. Fridericia's cube-root formula has been shown to perform better in correcting the QT interval for heart rate. Other formulas require the measurement of several QT-RR pairs at various heart rates to obtain a reliable QT_c interval and are therefore not easily usable. Any correction formula is likely to introduce an error in assessing the QT_c interval. Although the importance of this error should not be minimized, the corrected QT interval remains useful in assessing the effects of drugs on the duration of repolarization. For this purpose, Fridericia's cube-root formula is preferable to Bazett's square-root formula. However, correcting the QT interval for heart rate may conceal important information, such as the kinetics of QT-interval adaptation to a change in heart rate. The most reliable method for assessing the QT interval during drug administration is to avoid QT correction and to measure QT intervals at fixed heart rates.

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Rate-corrected QT interval: Techniques and limitations

Abstract

J Clin Epidemiol

Am J Cardiol

Prog Cardiovasc Dis

Am Heart J

J Electrocardiol

Am J Cardiol

Am J Cardiol

Am J Cardiol

Med Clin North Am

Am J Cardiol

J Electrocardiol

Am J Cardiol

Am J Cardiol

Am J Cardiol

Am J Cardiol

Am J Med

QTc prolongation measured by standard 12-lead electrocardiography is an independent risk factor for sudden death due to cardiac arrest

Circulation

QT interval prolongation predicts cardiovascular mortality in an apparently healthy population

Circulation

Is QT interval prolongation a strong or weak predictor for cardiac death?

Circulation

K+ channel blockers and activators in cardiac arrhythmias

Cardiovasc Drug Rev

La repolarisation ventriculaire

Arch Mal Coeur

QT_c prolongation measured by standard 12-lead electrocardiography is an independent risk factor for sudden death due to cardiac arrest

K⁺ channel blockers and activators in cardiac arrhythmias