INTRODUCTION
The QT interval is an electrocardiogram (ECG) representation of
ventricular depolarization and repolarization.1Torsades de pointes (TdP) is a life-threatening polymorphic ventricular
tachycardia associated with QT interval prolongation.1The risk for TdP increases as the heart-corrected QT (QTc) interval
increases, specifically when it exceeds 500 milliseconds
(ms).2 The American Heart Association and the American
College of Cardiology Foundation have published a scientific statement
to raise awareness on the risk, ECG monitoring, and management of
drug-induced QTc interval prolongation and TdP in hospitalized
patients.3 Several risk factors contribute to QTc
prolongation including increased age, female gender, QTc-prolonging
medications, presence of cardiovascular disease, renal failure and
electrolyte abnormalities.4
Clinical Decision Support Systems (CDSS) including alert generation for
drug-drug interactions (DDIs) are designed to improve clinical decision
making. Since QTc prolongation in hospitalized patients increases the
risk of TdP, many institutions employ alerts within their prescribing
systems when more than one QTc-prolonging medication is prescribed.
However, a primary limitation of CDSS is alert desensitization, or alert
fatigue, where alerts are frequently overridden by clinicians due to
patient non-specificity or low risk.5
Multiple investigators have developed methods for risk quantification
through a QTc risk score. Tisdale et al.6 developed a
CDSS incorporating a weighted QTc risk score with 67-74% sensitivity
and 77-88% specificity that reduced both risk of QTc prolongation and
prescribing of non-cardiac medications known to cause TdP. Similarly,
investigators at the Mayo Clinic developed a QTc interval risk score
where they found a higher predicted mortality with a score of 4 or
greater; however, all risk factors were allocated one
point.7 Given the lacking evidence of how risk factors
should be weighed, a systematic analysis was conducted by Vandael et al.
to generate an evidence-based list of all risk factors associated with
QTc prolongation.8 Using the evidence per risk factor,
a preliminary risk score for QTc prolongation (RISQ-PATH) was developed
in an academic tertiary care medical center in Belgium, and points were
allocated in accordance with the evidence level in the systematic
review. The risk score was found to have a high sensitivity (96.2%) and
negative predictive value (NPV; 98%) with a cutoff of 10
points.9 This score was further optimized and
validated in a large patient cohort including 60,208 patients, where the
authors reported a sensitivity of ± 87% and a specificity of ±
45%.5