Application of the QT nomogram to ECG monitoring of QT prolongation in arsenic trioxide for acute promyelocytic myeloid leukaemia

Arsenic trioxide is used in the treatment of acute promyelocytic myeloid leukemia. QT prolongation is a potential risk with arsenic therapy and formulae which correct the QT for heart rate (QTc) may over-estimate the risk of torsades de pointes. We aimed to apply the QT nomogram, a risk assessment tool which predicts arrhythmogenic risk in drug-induced QT prolongation, to QT monitoring during arsenic therapy. This retrospective series of 29 patients treated with arsenic for acute promyelocytic myeloid leukemia found the QTc was elevated in 17/284 (6%) ECGs, of which only 4/284 (1%) were above the QT prolongation threshold, when plotted on the QT nomogram. Across the study period, there was a total of five patients with QTc ≥500 ms. Treatment was withheld in 14 instances for QTc prolongation, of which only two plotted above the QT prolongation threshold on the QT nomogram. There were no instances of arrhythmia.