In our article, QT interval and drug therapy, the Fridericia

In our article, QT interval and drug therapy, the Fridericia formula for correcting the QT interval for
heart rate [QTc=QT/(RR/3)] was taken from a review paper.1 Although the formula was reproduced
directly from the paper, it is incorrect. The Fridericia method was derived from a cube root
relationship based on the formula:
3
QT = 8.22 x √RR
The concept of the corrected QT interval (QTc), derived from the same empirical formula, was
introduced later:1,2
QTc =
3
QT
√RR
or
QTc =
QT
(RR)1/3
1. Nachimuthu S, et al. Drug-induced QT interval prolongation: mechanisms and clinical
management. Ther Adv Drug Saf 2012; 3: 241–53.
2. Fridericia LS. The Duration of Systole in an Electrocardiogram in Normal Humans and in Patients
with Heart Disease. Annals of Noninvasive Electrocardiology 2003; 8: 343-51.
3. Moss AJ . Introductory Note to a Translated Classic Article of L. S. Fridericia: L. S. Fridericia. Die
Systolendauer im Elektrokardiogramm bei normalen Menschen und bei Herzkranken (The Duration
of Systole in an Electrocardiogram in Normal Humans and in Patients with Heart Disease). Part I:
Beziehung zwischen der Pulsfrequenz und der Dauer des Ventrikelelektrokardiogramms bei
normalen Menschen in der Ruhe (Relationship of the pulse frequency and the duration of the
ventricular electrocardiogram in normal humans at rest). Acta Med Scand 1920; 53: 469–86. Annals
of Noninvasive Electrocardiology 2003; 8: 341-2.

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