title: Contributions of myocardial ischemia and heart rate to ST segment changes in patients with or without coronary artery disease.
abstract: BACKGROUND
  ST changes related to ischemia at different heart rates (HRs) have not been well described. We aimed to analyze ST dynamic changes by vectorcardiography (VCG) during pacing-induced HR changes for subjects with proven coronary artery disease (CAD) and without (non-CAD).
  
  
  METHODS
  Symptomatic CAD patients scheduled for elective surgery were enrolled along with a non-CAD group. During anesthesia, both groups were placed at multiple ascending levels. VCG ST data, and in particular in ST change vector magnitude (STC-VM) from baseline, along with arterial and great coronary artery vein (GCV) blood samples were collected to determine regional myocardial lactate production.
  
  
  RESULTS
  A total of 35 CAD and 10 non-CAD patients were studied over six incremental 10 beat/min HR increases. STC-VM mean levels increased in the CAD group from 9+/-5 to 131+/-37 microV (standard deviation) compared with non-CAD subjects with 8+/-3-76+/-34 microV. Myocardial ischemia (lactate production) was noted at higher HRs and the positive predictive value for STC-VM to detect ischemia was 58% with the negative predictive value being 88%. STC-VM at 54 microV showed a sensitivity of 88% and a specificity of 75% for identification of ischemia.
  
  
  CONCLUSIONS
  Both HR and ischemia at higher HRs contribute to VCG ST elevation. Established ST ischemia detection concerning HR levels is suboptimal, and further attention to the effects of HR on ST segments is needed to improve electrocardiographic ischemia criteria.
authors.affiliation: Heart Centre, University Hospital, Umeå, Sweden. soren.haggmark@vll.se
authors.forename: S
authors.initials: S
authors.lastname: Häggmark
authors.forename: M F
authors.initials: MF
authors.lastname: Haney
authors.forename: G
authors.initials: G
authors.lastname: Johansson
authors.forename: S
authors.initials: S
authors.lastname: Reiz
authors.forename: U
authors.initials: U
authors.lastname: Näslund
mesh_terms: D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000503:physiopathology; D001794:Blood Pressure; D002304:Cardiac Pacing, Artificial / Q000379:methods; D003324:Coronary Artery Disease / Q000150:complications*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods / Q000706:statistics & numerical data; D017202:Myocardial Ischemia / Q000150:complications*; D011237:Predictive Value of Tests; D014672:Vectorcardiography / Q000379:methods* / Q000706:statistics & numerical data*
chemical_list: D019344:Lactic Acid