Although ibrutinib-associated atrial and ventricular arrhythmias have been well described, there is little information about ibrutinib's effects on other electrocardiographic parameters, particularly the QT interval. Using our database of 137 patients treated with ibrutinib, we retrospectively identified 21 patients in whom an electrocardiogram (ECG) was obtained both prior to and after ibrutinib exposure. All traditional ECG parameters as well as QT dispersion were manually measured by an electrophysiologist. Compared to baseline ECGs, post ibrutinib ECGs demonstrated QT interval shortening from 386 ms to 356 ms (P = .007), corrected QT interval shortening using Bazett's formula from 446 ms to 437 ms (P = .04), and corrected QT interval shortening using Fridericia's formula from 425 ms to 407 ms (P = .003). QT dispersion also increased post ibrutinib exposure compared to baseline (39.8 ms vs 57.3 ms, P = .002). There was no significant change in other ECG parameters. In conclusion, both the absolute and corrected QT intervals significantly shortened after ibrutinib exposure, while there was a significant increase in QT dispersion. These findings may point to a common underlying electrophysiologic mechanism of ibrutinib-associated arrhythmias.
Keywords: QT interval; cardio-oncology; cardiotoxicity; electrocardiogram; ibrutinib.