Prescribers' practice of assessing arrhythmia risk with QT-prolonging medications

This study aimed to assess prescribers' monitoring for arrhythmic risk with QT-prolonging medications (LQT drugs).

Over a 6-month period, all inpatients under the care of Cardiologists (Cohort A) and General Physicians (Cohort B) at Aberdeen Royal Infirmary who were prescribed drugs with known risk of Torsades de Pointes (TdP) were identified. Admission and repeat electrocardiograms (ECG) after 48 h of commencing a LQT drug were examined. Actions taken if QTc was prolonged and drug-drug interactions were examined. A risk estimate on the UK hospital population was calculated.

Of the 4133 patients admitted during the study period, 234 (6%) patients were prescribed a LQT drug. There were 100 (43%) patients in Cohort A and 134 (57%) patients in Cohort B. Of those admitted with a pre-existing LQT drug prescription, an ECG was performed in 167 (96%) of patients and QTc prolongation was identified in 59 (34%). Of those who received a new prescription of LQT drug, 23 (38%) had QTc prolongation and more patients in Cohort A than Cohort B had a repeat ECG within 48 h (84% vs. 11%, P < 0.0001). QTc prolongation was only recognized in 6 (14%) and 2 (5%) patients in cohorts A and B, respectively. Only one patient at risk of drug interaction had QTc prolongation. None of our patients had documented TdP in hospital. Extrapolating these findings to the UK hospital population, at least 204 and <17-175 patients on cardiac and noncardiac LQT drugs, respectively, might be expected to have TdP each year.

Recognition of acquired QTc prolongation is poor. Clinician education and an electronic prescribing system may improve this situation.