Abstract 1200: QT-Prolonging Medication Prescription Tendencies In A Cohort Of Hospitalized Patients With Known Long QT Intervals
Background: QT interval prolongation is an important risk factor for sudden cardiac death. Certain drugs are known to prolong the QT interval and thus should be avoided in most patients with preexisting long QT intervals. However, no studies have investigated prescribing habits for these contraindicated medications in hospitalized patients with preexisting long QT intervals.
Methods: We have developed an anonymized database of all inpatient orders, laboratory results, and electrocardiograms (ECGs) for all inpatients admitted for 2–30 days from 1999 –2003 to investigate drug effects. The database contains 44,808 ECGs, including machine-calculated intervals and the cardiologist-generated report. We identified patients with long QT intervals specifically mentioned in an ECG narrative report using previously-validated methods. We retrieved inpatient medication orders for prescriptions of 28 known QT-prolonging medications that were ordered after an ECG demonstrated a long QT. We also searched for the presence of concomitant interacting medications.
Results: There were 1,586 patients with 2,616 ECGs demonstrating a long QT interval. These patients had 3,258 admissions. More than a third of these patients (599 patients, 37.8%) received an order for a QT-prolonging medication after a report of QT prolongation. Only 8% had a repeat ECG within 48 hours of the new medication order. Two-thirds of these patients were critical care patients. Anti-arrhythmics accounted for more than half of those medications (52.6%). Haloperidol prescriptions accounted for 636 (30.0%) of the remaining prescriptions; 83.7% were ordered intravenously. Only 30 (1.5%) patients also had prescriptions for a concomitant interacting medication.
Conclusion: Providers commonly order QT prolonging medications in patients with known preexisting long QT intervals. These patients were rarely monitored for further prolongation of their QT interval. Automated prescribing interventions could potentially reduce such inappropriate prescriptions, formalize surveillance procedures if such medicines are used, and thus reduce the risk of adverse outcomes.