A prolonged QTc-interval at the emergency department: Should we always be prepared for the worst?

J Cardiovasc Electrophysiol. 2019 Oct;30(10):2041-2050. doi: 10.1111/jce.14114. Epub 2019 Aug 21.

Abstract

Introduction: QTc-interval prolongation is associated with ventricular arrhythmias and mortality in a general population. Bazett's correction formula (QTcB) is routinely used despite its overcorrection at high heart rates. Recently, we proposed a patient-specific QT correcting algorithm (QTcA) resulting in improved rate correction and predictive value in a general population. We hypothesize risk stratification at the Emergency Department (ED) could be improved using QTcA.

Methods and results: A retrospective case-control study including a randomized age- and sex-matched control population was performed at a tertiary care ED. A total of 1930 patients were included in the analysis (63.0% males, age 71.5 ± 15.6 years). Patient characteristics, history, and test results at the time of the electrocardiogram were collected. QTc was dichotomized as prolonged (>450 millisecond for men, >470 millisecond for women) or severely prolonged (>500 millisecond). Implementation of QTcA would reduce the number of patients considered to have a prolonged QTc by 65.2%, for severely prolonged QTc 79.6%. Multivariate regression was performed for in-hospital mortality, cardiovascular endpoints, and hospital admission. Neither a prolonged QTcB (HR 1.04; 95% CI, 0.64-1.69) nor QTcA (HR 0.76; 95% CI, 0.42-1.38) was an independent predictor of in-hospital mortality. A severely prolonged QTcA (OR, 2.54; 95% CI, 1.04-6.23) was an independent predictor of cardiovascular events. Both a prolonged QTcA (OR, 1.52; 95% CI, 1.06-2.18) and a prolonged QTcB (OR, 1.37; 95% CI, 1.05-1.79) were associated with higher hospitalization rates.

Conclusions: QTcA reduced the number of patients considered at risk. Neither QTcB nor QTcA were predictors of in-hospital mortality. A severely prolonged QTcA was associated with cardiovascular events.

Keywords: QTc-interval; cardiovascular events; emergency department; hospitalization rate; mortality.

MeSH terms

  • Action Potentials*
  • Aged
  • Aged, 80 and over
  • Algorithms*
  • Arrhythmias, Cardiac / diagnosis*
  • Arrhythmias, Cardiac / mortality
  • Arrhythmias, Cardiac / physiopathology
  • Arrhythmias, Cardiac / therapy
  • Electrocardiography*
  • Emergency Service, Hospital*
  • Female
  • Heart Conduction System / physiopathology*
  • Heart Rate*
  • Hospital Mortality
  • Humans
  • Male
  • Middle Aged
  • Patient Admission
  • Predictive Value of Tests
  • Prognosis
  • Reproducibility of Results
  • Retrospective Studies
  • Risk Assessment
  • Risk Factors
  • Signal Processing, Computer-Assisted*
  • Time Factors