Incidence of QT interval prolongation during arsenic trioxide-based therapy in a sample of Iraqi adult patients with acute promyelocytic leukemia (a single-center experience)

Abstract

Arsenic trioxide (ATO) regimen is now the standard of care for acute promyelocytic leukemia (APL). The complete remission and possible cure are reported to be 50%–80% of APL patients. Prolongation of the QT interval has been consistently observed in clinical trials with ATO, which is known to have a direct effect on cardiac repolarization with the recommendations for management include electrocardiogram (ECG) monitoring, discontinuation of drugs that prolong the QT interval, and careful repletion of serum potassium and magnesium. To study the incidence and clinical consequences of QT prolongation in a sample of Iraqi APL patients treated with ATO. A prospective, cross-sectional study was conducted on 24 adult patients with newly diagnosed APL at Baghdad Teaching Hospital. ECG was performed at baseline and twice weekly till the end of induction treatment course. Corrected QT interval was calculated based on Bazett and Fridericia formulas (QTc interval of more than 500 ms is considered dangerous): Serum potassium, calcium, and magnesium levels were also measured simultaneously. The mean QT at baseline was 424 ± 18 ms and 402 ± 15 ms by Bazett and Fridericia, respectively, and at the end of induction, the mean QT was 436 ± 20 ms and 418 ± 20 ms by Bazett and Fridericia, respectively. The rate of developing prolonged QT was 62.5% by Bazet, in which 15 patients developed prolonged QT (at any time point). The comparison between prolonged and dangerous QT groups by Bazet showed significant difference, in which QT-related complications were associated with dangerous QT (>500 ms) prolongation significantly, while Fridrica method did not label these patients as having dangerous QT prolongation. The change in QT started as early as 1 week after treatment, the comparison between baseline QT and QT at week 1 showed that there was significant increase in QT. The electrolytes analysis and comparison with baseline results for potassium, magnesium, and calcium showed that there were no significant differences over time for tested electrolytes. Bazett formula is useful to monitor Iraqi patients with APL who are treated with ATO for the detection of dangerous prolongation of QT.