title: Detection of stress-induced myocardial ischemia from the depolarization phase of the cardiac cycle--a preliminary study.
abstract: BACKGROUND
  Electrocardiogram (ECG)-based detection of ischemia is typically dependent on identifying changes in repolarization. Analysis of high-frequency QRS (HFQRS) components, related to the depolarization phase of the cardiac action potential, has been reported to better identify ischemia. Our aim was to test the hypothesis that HFQRS analysis is both more sensitive and specific than standard ECG for detecting exercise-induced ischemia in patients undergoing exercise myocardial perfusion imaging (MPI).
  
  
  METHODS
  Exercise MPI was performed in 133 consecutive patients (age, 63 +/- 12; 100 males) and used as the gold standard for ischemia. Patients with QRS duration more than 120 milliseconds (n = 20), technical problems (n = 8), or inconclusive MPI (n = 4) were excluded, leaving 101 patients for analysis. Conventional ECG was combined with high-resolution ECG acquisition that was digitized and analyzed using the HyperQ System (BSP, Tel Aviv, Israel). The relative HFQRS intensity change during exercise was used as an index of ischemia.
  
  
  RESULTS
  Of the 101 patients who were included in the analysis, 19 exhibited MPI ischemia. The HFQRS index of ischemia was found to be more sensitive (79% vs 41%; P < .05) and more specific (71% vs 57%; P < .05) than conventional ST analysis.
  
  
  CONCLUSIONS
  The HFQRS analysis was more sensitive and specific than conventional ECG interpretation in detecting exercise-induced ischemia and exhibited enhanced diagnostic performance in both women and men. Thus, it may aid in the noninvasive diagnosis of ischemic heart disease.
authors.affiliation: Research and Development, BSP Ltd., Tel Aviv, Israel. eran@bspmedical.com
authors.forename: Eran
authors.initials: E
authors.lastname: Toledo
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Lipton
authors.forename: Stafford G
authors.initials: SG
authors.lastname: Warren
authors.forename: Shimon
authors.initials: S
authors.lastname: Abboud
authors.forename: Mike
authors.initials: M
authors.lastname: Broce
authors.forename: Donald R
authors.initials: DR
authors.lastname: Lilly
authors.forename: Charles
authors.initials: C
authors.lastname: Maynard
authors.forename: B Daniel
authors.initials: BD
authors.lastname: Lucas
authors.forename: Galen S
authors.initials: GS
authors.lastname: Wagner
mesh_terms: D000465:Algorithms; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity