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Predictive Validity of a QTc Interval Prolongation Risk Score in the Intensive Care Unit.

Authors
  • Su, Ke1
  • McGloin, Rumi2, 3
  • Gellatly, Rochelle M2, 3, 4
  • 1 Pharmacy Department, Royal Columbian Hospital, New Westminster, British Columbia, Canada. , (Canada)
  • 2 Pharmacy Department, Surrey Memorial Hospital, Surrey, British Columbia, Canada. , (Canada)
  • 3 Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada. , (Canada)
  • 4 Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia. , (Australia)
Type
Published Article
Journal
Pharmacotherapy
Publication Date
Jun 01, 2020
Volume
40
Issue
6
Pages
492–499
Identifiers
DOI: 10.1002/phar.2400
PMID: 32259316
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Torsade de pointes is a form of polymorphic ventricular tachycardia associated with heart rate-corrected QT (QTc ) interval prolongation. With approximately 24-61% of critically ill patients experiencing QTc interval prolongation, a predictive tool to identify high-risk patients could assist in the monitoring and management in the intensive care unit (ICU). The Tisdale et al. Risk Score (TRS) is a predictive tool that was developed and validated in a cardiac critical care unit. The objective of this study was to evaluate the predictive validity (sensitivity and specificity) and likelihood ratios of the TRS in a medical ICU. This was a longitudinal, retrospective, cohort study of consecutive patients who met the inclusion criteria from October 2017 to June 2018 with a sample size of 264 patients. The sample size was derived based on the number of TRS covariates and an exploratory variable. Baseline characteristics and risk factors were documented from electronic health records. The first occurrence of QTc interval prolongation, defined as a QTc interval > 500 ms or an increase ≥ 60 ms above baseline, was the primary endpoint. The sensitivity and specificity of the TRS for low-risk patients against the moderate-risk and high-risk patients were 97% (95% CI 91-99%) and 16% (95% CI 11-23%), respectively. These results corresponded to a positive likelihood ratio of 1.15 (95% CI 1.07-1.24) and a negative likelihood ratio of 0.20 (95% CI 0.06-0.65). In conclusion, the TRS showed a high sensitivity, making it useful in identifying patients at risk of developing QTc interval prolongation. Furthermore, patients categorized as low risk by the tool can be considered as having minimal risk of developing QTc interval prolongation. Given the tool's low specificity, it does not reliably identify all patients at low risk of QTc interval prolongation. © 2020 Pharmacotherapy Publications, Inc.

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