title: High-frequency QRS electrocardiogram analysis during exercise stress testing for detecting ischemia.
abstract: BACKGROUND
  ECG stress testing is an inexpensive and non-invasive detector of myocardial ischemia; addition of high-frequency QRS analysis (HFQRS) may improve accuracy. This study compared HFQRS during exercise in patients with and without ischemia as defined by multiple criteria.
  
  
  METHODS
  High-resolution ECGs were recorded for 139 patients undergoing T99-sestamibi/T201-thallium stress testing. Twenty-three were positive by at least two and 37 were negative for ischemia by all three of the following criteria: nuclear scan, ST-segment analysis and typical angina. Sixty-four not meeting criteria for positive or negative, six with adenosine test and nine patients with ECG recording artifacts were excluded. Mean age of the study group was 62+/-10 years, 83% were male. Ischemic patients had a higher incidence of previous myocardial infarction and coronary intervention than non-ischemic patients (74% vs. 46%; P=0.03 and 70% vs. 43%; P=0.05, respectively), but had a lower body mass index (28.7+/-5 vs. 33.0+/-8; P=0.015). HFQRS analysis consisting of signal averaging (150-250 Hz) and calculation of root mean squared values for each lead at different time points was performed and was similar between the groups. The relative change in HFQRS (RCQ) was calculated for each lead: {(maxHFQRS-minHFQRS)/maxHFQRS}. For each patient an RCQ index was calculated by averaging the two leads with the greatest RCQ value. The RCQ index was greater in ischemic vs. non-ischemic patients (45% vs. 34%; P=0.0069).
  
  
  CONCLUSIONS
  Maximum decrease in HFQRS, as quantified by RCQ index, was greater in ischemic vs. non-ischemic patients. Use of the RCQ index may improve the diagnosis of ischemia during exercise stress testing.
authors.affiliation: Erasmus Medical Center, Rotterdam, The Netherlands. jonathanlipton@gmail.com
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Lipton
authors.forename: Stafford G
authors.initials: SG
authors.lastname: Warren
authors.forename: Mike
authors.initials: M
authors.lastname: Broce
authors.forename: Shimon
authors.initials: S
authors.lastname: Abboud
authors.forename: Amir
authors.initials: A
authors.lastname: Beker
authors.forename: Leif
authors.initials: L
authors.lastname: Sörnmo
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: D000368:Aged; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis*; D011336:Probability; D012016:Reference Values; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D017256:Technetium Tc 99m Sestamibi
chemical_list: D017256:Technetium Tc 99m Sestamibi