Download prescribers practice of assessing arrhythmia risk with qt

PRESCRIBERS PRACTICE OF ASSESSING ARRHYTHMIA RISK WITH
QT-PROLONGING MEDICATIONS
Wai Kah Choo , David Turpie, Kim Milne, Lynne Dowswell, Petrus Elofuke, Jonathan Whitfield, Paul
Broadhurst (Aberdeen Royal Infirmary, Aberdeen, United Kingdom)
Introduction: Acquired QTc prolongation from drug therapy is well known. Such drugs are widely
prescribed and their pro-arrhythmic risks are often under recognised. This study aimed to assess
prescribers’ monitoring for arrhythmic risk with QT-prolonging medications (LQT drugs).
Methods: Over a 6-month period, all inpatients under the care of Cardiologists (Cohort A) and General
Internal Physicians (Cohort B) at Aberdeen Royal Infirmary prescribed LQT drugs were identified.
Only drugs with known risk of Torsades de Pointes (TdP) defined by The Arizona CERT website were
studied. Admission and repeat electrocardiograms (ECG) after 48 hours of commencing a LQT drug
were examined. Actions taken if QTc was prolonged were identified and drug-drug interaction
examined. The results were extrapolated to estimate the risk of TdP from LQT drugs to the UK hospital
population.
Results: Of the 4133 patients admitted during the study period, 234 patients were prescribed a LQT
drug (100 in Cohort A and 134 in Cohort B).
Of those (75%) admitted with a pre-existing LQT drug prescription, an ECG was performed in all
patients in Cohort A and 93% in cohort B. A combined total of 34% in this subgroup had a prolonged
QTc. Of those (25%) who received a new prescription of LQT drug, significantly more patients in
Cohort A had a repeat ECG within 48 hours of commencing a LQT drug compared to Cohort B (84%
vs. 11%, p < 0.0001). Only 6 patients (14%) in Cohort A and 2 patients (5%) in Cohort B with a
prolonged QTc were recognised as such by their clinicians. The LQT drug was stopped in one patient
from each cohort. Primary care physicians were notified of QTc prolongation in 2 cases. Sixteen
patients (7%) across both cohorts were on two LQT drugs. Only one patient at risk of drug interaction
had QTc prolongation.
Observed rates of TdP with antiarrhythmics are thought to be >1% and non-cardiac drugs between
<0.01% and 0.1%; none of our patients had documented TdP in hospital. Extrapolating our study
findings to the UK hospital population, we estimate that at least 204 and between <17 and 175 patients
on cardiac and non-cardiac LQT drugs respectively might be expected to have TdP.
Conclusion: Recognition of acquired QTc prolongation is poor. Clinician education and/or an
electronic prescribing system may improve this situation.