(Acta Anaesth. Belg., 2015, 66, 101)
Letter to the Editor
Heart rate correction should be kept in mind during measurements
of ventricular repolarization parameters
M. Dogan, O. Yıgıner, H. Un and I. Dagasan
Key words : Magnesium sulfate ; tracheal intubation ;
QT dispersion ; Tp-e ; transmural dispersion.
We read the article entitled “A comparison of
the effects of lidocaine or magnesium sulfate on
­hemodynamic response and QT dispersion related
with intubation in patients with hypertension” by
Kiraci et al. with interest (1). The authors investigated the effects of magnesium on the hemodynamic, QT interval and QT interval dispersion(QTd)
changes during anesthesia induction in hypertensive
patients that compared to lidocaine. Finally, they
concluded magnesium sulfate may be useful for
­patients who develop QTd increase during tracheal
intubation, especially in coronary artery disease
­patients. We would like to thank to the authors for
their valuable contribution. On the other hand, we
would like to report a few concerns regarding this
study from a methodological point of view.
The QT interval is dependent on the heart rate.
It is inversely proportional to heart rate : The QT
shortens at faster heart rates and lengthens at slower
heart rates. In order to improve the detection of increased ventricular arrhythmia risk, some formulas
are used for QT correction such as Bazett’s and
Fredericia’s (Bazett Formula : Corrected QT(QTC) =
QT/(RR)0.5 and Fredericia Formula : Tc = QT/
(RR)0.333). If the authors had used these corrected QT
formulas, that would make the study more precise.
In addition to QTd, transmural dispersion of
repolarization (TDR) quantifies myocardial inhomogeneity (2). Isolated cells from different layers
of the myocardium revealed that myocardium
­consists of three different myocyte types : i) endocardial, ii) epicardial, and iii) midmyocardial M
cells (3). These myocyte types have various electrophysiological characteristics. This heterogeneity
may cause to electrical instability and are measurable on surface ECG. Epicardial repolarization
phase ends at the peak of the T-wave, M cells repolarization continues until the end of the T wave (3).
Thus, the distance between the peak and end of the
T wave is entitled as Tp-e interval, which reflects
TDR. Previously, we presented that TDR was increased in patients with obstructive sleep apnea and
chronic arsenic exposure via drinking water (4, 5).
It has been also demonstrated that TDR is increased
in ST-elevation myocardial infarction (3). Adding
TDR measurements might have been better for
determining the arrhythmic risk during tracheal
­
­intubation in hypertensive patients.
We believe that the paper of Kiraci et al. will
lead to further studies concerning myocardial
­heterogeneity and instability. However, assessment
of Tp-e and corrected QT interval should be kept in
mind to provide more comprehensive data.
References
1.Kiraci G., Demirhan A., Tekelioglu U. Y., Akkaya A.,
Bilgi M., Erdem A., Bayir H., Yildiz I., Kocoglu H., A
comparison of the effects of lidocaine or magnesium sulfate
on hemodynamic response and QT dispersion related with
intubation in patients with hypertension, Acta Anaesthesiol.
Belg., 65, 81, 2014.
2. Antzelevitch C., T peak-Tend interval as an index of trans­
mural dispersion of repolarization, Eur. J. Clin. Invest., 31,
555-7, 2001.
3. Gupta P., Patel C., Patel H., Narayanaswamy S., Malhotra B.,
Green J. T., Yan G. X., T(p-e)/QT ratio as an index of
arrhythmogenesis, J. Electrocardiol., 41, 567-74, 2008.
4.Kilicaslan F., Tokatli A., Ozdag F., Uzun M., Uz O.,
Isilak Z., Yiginer O., Yalcin M., Guney M. S., Cebeci B. S.,
Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio are
prolonged in patients with moderate and severe obstructive
sleep apnea, Pacing Clin. Electrophysiol., 35, 966-72,
2012.
5.Yildiz A., Karaca M., Biceroglu S., Nalbantcilar M. T.,
Coskun U., Arik F., Aliyev F., Yiginer O., Turkoglu C. J.,
Effect of chronic arsenic exposure from drinking waters on
the QT interval and transmural dispersion of repolarization,
Int. Med. Res., 36, 471-8, 2008.
Mehmet Dogan ; Omer Yıgıner ; Haluk Un ; Ibrahim ­Dagasan.
Gulhane Military Medical Academy, Haydarpasa Training
Hospital Department of Cardiology, Istanbul, Turkey.
Correspondence addresss : Mehmet Dogan, Gulhane Military
Medical Academy, Haydarpasa Training Hospital Department of Cardiology, Istanbul, Turkey.
E-mail : mehmetdoganmd@yahoo.com
© Acta Anæsthesiologica Belgica, 2015, 66, n° 3
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