The letter by Drs Szabo and Andrássy highlights 2 points: (1) mental stress rather than ketosis could account for QTc prolongation during DKA and (2) the Bazett formula can be inaccurate, particularly at elevated heart rates. The reference that Szabo and Andrássy cite regarding the effect of mental stress on QTc appears to be a non–peer-reviewed doctoral thesis.1 Furthermore, in our article,2 we acknowledge the controversy regarding how to best adjust the QT interval for heart rate. We selected the Bazett method, as it is the one most commonly used in practice, despite known intersubject variability in the QT/RR relation.3
Kuppermann N, Park J, Glaser N. Prolonged QT Interval Corrected for Heart Rate During Diabetic Ketoacidosis in Children: Psychological Stress Could Be Another Explanation—Reply. Arch Pediatr Adolesc Med. 2009;163(1):92–93. doi:10.1001/archpediatrics.2008.518
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