Chloroquine-induced QTc prolongation in COVID-19 patients.

van den Broek, M P H; Möhlmann, J E; Abeln, B G S; Liebregts, M; van Dijk, V F; van de Garde, E M W; van den Broek, M. P. H.; Möhlmann, J. E.; Abeln, B. G. S.; Liebregts, M.; van Dijk, V. F.; van de Garde, E. M. W.

BACKGROUND In the battle against the SARS-CoV‑2 pandemic, chloroquine has emerged as a new potential therapeutic option for the treatment of infected patients. A safety consideration for the application of chloroquine is its QTc-prolonging potential. Thus far, no data are available on the QTc-prolonging potential of chloroquine in COVID-19 patients. OBJECTIVE To assess the degree of chloroquine-induced QTc prolongation in hospitalised COVID-19 patients. METHODS A baseline electrocardiogram (ECG) and ECGs recorded during chloroquine treatment were retrospectively collected in patients suspected of having COVID-19. The QTc interval was calculated by computerised and manual interpretation. Baseline and follow-up QTc intervals were compared using the paired samples t-test. RESULTS A total of 95 patients had a baseline ECG recording and at least one ECG recording during chloroquine therapy. Chloroquine treatment resulted in a mean QTc prolongation of 35 ms (95% CI 28-43 ms) using computerised interpretation and 34 ms (95% CI 25-43 ms) using manual interpretation. No torsade de pointes was observed during chloroquine treatment. After manual review, 22 patients (23%) had a QTc interval exceeding 500 ms during chloroquine treatment. None of these patients had a prolonged QTc interval prior to the initiation of chloroquine treatment. CONCLUSIONS Chloroquine significantly prolongs the QTc interval in a clinically relevant matter. This highlights the need for ECG monitoring when prescribing chloroquine to COVID-19 patients.