Several factors can alter the QTc interval in patients with end-stage renal disease.

To the Editor,

I read with great interest the paper by Temiz et al. (1) entitled “Effects of cinacalcet treatment on QT interval in hemodialysis patients” published as Epub ahead of print for The Anatolian Journal of Cardiology 2015. They aimed to evaluate the effects of a calcimimetic drug (cinacalcet) on corrected QT values (QTc) in patients with end-stage renal disease (ESRD). They found a prolongation of QTc value compared with baseline QTc value after cinacalcet treatment. I have a few comments.

QTc interval is the time from beginning of QRS to the end of T wave. In other words, it consists of depolarization and repolarization phases of cardiac tissue. Prolongation of QTc represents delayed cardiac repolarization and can be related to ventricular arrhythmias and sudden cardiac death (2, 3). Although it is well-known that QTc prolongation is common in patients with ESRD, the exact mechanism of this cardiac repolarization abnormality has not been established (2–5). Hemodialysis is one reason QTc interval may be affected. Researchers have demonstrated increased QTc intervals in patients with ESRD, especially after end of hemodialysis. This is largely attributed to rapid changes in plasma electrolyte levels during hemodialysis (4). Therefore, it is crucial exactly when electrocardiography (ECG) is performed. In the study by Temiz et al. (1), it is possible that the timing of ECG may have influenced measurement of QTc.

Electrolyte disturbances are common in patients with ESRD and can cause changes in cardiac ionic polarization, resulting in altered QTc interval (2–5). Foglia et al. (5) determined QT prolongation in patients with primary renal hypokalemia-hypomagnesemia, and demonstrated that decreased levels of potassium and magnesium could alter duration of action potential in cardiac cell membrane. In the study by Temiz et al. (1), it may be helpful to present electrolyte levels of the patients at the time of ECG whether electrolytes have influential effects on QTc measurements or not.

Finally, measurement of QTc interval has some technical difficulties such as presence of U waves or inverted T waves and intraobserver variability, which are not mentioned clearly in the study by Temiz et al. (1) and can affect the precise measurement of QTc value (2–5).

In conclusion, I think that this study would be stronger with these additional data mentioned above and we can easily understand the role of cinacalcet on QTc interval in patients with ESRD.