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ECG machine QTc intervals are inaccurate in hemodialysis patients

B K A Thomson1, B Momciu, S H S Huang

  • 1London Health Sciences Centre and Western University, London, Ont., Canada.

Nephron. Clinical Practice
|November 7, 2013
PubMed

Insights

Machine-measured QTc (macQTc) intervals are unreliable for identifying hemodialysis patients with prolonged true QTc intervals. A macQTc threshold of >480 ms improves prediction but lacks sensitivity for detecting prolonged true QTc.

Area of Science:

  • Cardiology
  • Nephrology
  • Electrocardiography

Background:

  • Sudden cardiac death is the leading cause of mortality in hemodialysis patients.
  • Prolonged QTc intervals are associated with increased risk of sudden cardiac death.

Purpose of the Study:

  • To evaluate the accuracy of machine-measured QTc (macQTc) in identifying prolonged true QTc intervals in hemodialysis patients.
  • To determine a reliable macQTc threshold for diagnosing prolonged true QTc.

Main Methods:

  • Retrospective review of ECGs and patient charts of hemodialysis patients.
  • Comparison of machine-measured QTc (macQTc) with gold standard tangent method (trueQTc).

Main Results:

  • macQTc differed from trueQTc by an average of 16.54 ms.
  • macQTc showed low positive predictive value (57.6%) and sensitivity (79.1%) for prolonged trueQTc.
  • A macQTc threshold >480 ms achieved 95.2% positive predictive value but only 32.3% sensitivity.

Conclusions:

  • ECG macQTc intervals are insufficiently sensitive or specific to predict prolonged trueQTc in hemodialysis patients.
  • A macQTc threshold >480 ms may identify some patients with prolonged trueQTc but misses many.
  • More accurate screening tools are needed for hemodialysis patients at risk of sudden cardiac death.
Abstract

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