Reply

We read with interest the comments by Lee and Chik.[1] The goal of our study[2] was to assess the prevalence of QT prolongation in the hospital and to determine patient factors and drugs that are associated with such a prolongation. As Lee and Chik correctly pointed out, our study did neither have the power nor the necessary follow-up duration to compare the incidence of torsades de pointes and cardiovascular mortality. Given the relatively low incidence of such outcome events, such a study would not only require a prospective design but also the inclusion of several thousand patients with a follow up of several months. This was clearly beyond the scope of our project.

Among the 490 patients who were discharged alive from hospital, 204 (41.6%) have been discharged with the prescription of at least one medication with the potential to prolong the QT interval. These medications included mostly psychotropic drugs (citalopram, quetiapine, haloperidol, venlafaxine, paroxetine, risperidone, fluoxetine, lithium, sertraline, diphenhydramine and amitriptyline) and anti-infectious agents (levofloxacin, ciprofloxacin, clarithromycin, trimethoprim/sulphamethoxazole, azithromycin, fluconazole, moxifloxacin, atazanavir, voriconazole and erythromycin). Sixty (23%) of these drugs were QT drugs from list 1 and 97 (37%) from list 2. While most of the anti-infection agents probably had short prescription duration, this may not have been the case for the psychotropic drugs.

We hope that this additional information will be helpful to clinicians and that future studies will help answer the question about the prognostic impact of prescribing QT-prolonging drugs in hospital.