PHARMACOEPIDEMIOLOGY AND PRESCRIPTION QT interval prolongation in hospitalized patients on cardiology wards: a prospective observational study Qasim Khan 1,2 & Mohammad Ismail 1 & Iqbal Haider 3 & Inam ul Haq 1 & Sidra Noor 1 Received: 28 March 2017 /Accepted: 4 August 2017 # Springer-Verlag GmbH Germany 2017 Abstract Purpose Prolonged QT interval may lead to a lethal form of arrhythmia, torsades de pointes (TdP), which is associated with cardiovascular mortality. Therefore, we aimed to identify prevalence of QT interval prolongation, compare clinical char- acteristics of patients with normal and prolonged QT interval, and identify predictors of QT interval prolongation. Methods A prospective observational study was conducted in cardiology wards of two teaching hospitals in Pakistan. Bazett’ s correction formula was used for the calculation of QTc interval. Prevalence of QT prolongation and pro-QTc scores were calculated. Comparative analysis was performed with respect to various clinical characteristics by applying t test and chi-square test. Odds ratios were calculated using regression analysis. Results Among 417 patients, 44.6% were found having prolonged QT interval, of which, 17.3% presented with an abnormally high QTc interval (> 500 ms). Significant differ- ence was recorded between the groups (normal vs. prolonged) with respect to age, all prescribed medications, QT drugs, number of risk factors, QT-DDIs (QT-prolonging drug-drug interactions), gender, and diuretics use. Multivariate logistic regression analysis showed significant results for various pre- dictors such as male gender (p = 0.03), various age categories 41–50 years (p = 0.04), 51–60 years (p = 0.01), and > 60 years (p < 0.001), and diuretics (p = 0.008). Conclusion A substantial number of patients in cardiology wards presented with QT prolongation. Proper considerations are needed in order to minimize the associated risk particularly in patients with abnormally high QT prolongation, old age, polypharmacy, one or more QT-prolonging drugs, and high pro-QTc scores. Keywords QT prolongation . Cardiology . Torsades de pointes . QT-prolonging drugs . Pharmacoepidemiology Introduction Over three million people die yearly from sudden cardiac death (SCD) across the world [1]. The majority of these deaths are attributed to coronary artery disease (CAD) or other struc- tural aberrations, but a few occur as an outcome of arrhyth- mias [2–4]. Prolonged corrected QT (QTc) interval may lead to an erratic form of deadly arrhythmia, torsades de pointes (TdP) [5]. Drug-induced QT prolongation may lead to TdP [6]. Though there are marked fluctuations in an individual’ s QTc interval depending upon the heartbeat, the normal cutoff value for men is 430 ms and for women 450 ms [7]. Patients may become more susceptible to develop TdP when the QTc interval is greater than 500 ms [8]. A recent study dem- onstrated that lengthy hospital stay and all-cause mortality are associated with QT prolongation, and the most noticeable ad- verse outcome of prolonged QT interval is the development of TdP [9]. Numerous drugs have been associated with the Electronic supplementary material The online version of this article (doi:10.1007/s00228-017-2321-4) contains supplementary material, which is available to authorized users. * Mohammad Ismail ismailrph@upesh.edu.pk 1 Department of Pharmacy, University of Peshawar, Khyber Pakhtunkhwa, Pakistan 2 Department of Pharmacy, COMSATS Institute of Information Technology, Abbottabad, Pakistan 3 Department of Medicine, Khyber Teaching Hospital, Peshawar, Pakistan Eur J Clin Pharmacol DOI 10.1007/s00228-017-2321-4