title: Detection and quantification of acute myocardial ischemia by morphologic evaluation of QRS changes by an angle-based method.
abstract: OBJECTIVE
  In acute myocardial ischemia changes within the QRS complex can add valuable information to that from the repolarization phase. This study evaluates three angles obtained from the main slopes of the R-wave within the QRS complex to assess acute myocardial ischemia.
  
  
  METHODS
  The QRS angles, denoted by ØR (R-wave angle), ØU (up-stroke angle) and ØD (down-stroke angle), were evaluated in 12-lead electrocardiogram (ECG) recordings of 79 patients before and during coronary occlusion by elective percutaneous coronary intervention (PCI). In a subset of 38 patients, ischemia was quantified by myocardial scintigraphy.
  
  
  RESULTS
  At baseline the QRS angles presented low variations. During occlusion, ØU and ØD developed a fast and abrupt change, whereas ØR showed a smaller and gradual change. There were significant correlations between both maximal and sum of positive change in ØR and ischemia: r=0.67; p<0.001 and r=0.78; p<0.001, for extent, and r=0.60; p<0.001 and r=0.73; p<0.001, for severity, respectively. Prediction of extent and severity of ischemia increased by 50% by adding ØR changes to ST-segment changes, for LCX occlusions, whereas increased by 12.1% and 24.6% for LAD and RCA occlusions, respectively. No significant correlation was seen between ØU and ØD angles and ischemia.
  
  
  CONCLUSIONS
  Evaluation of QRS angles from the standard 12-lead ECG represents a sensitive marker for detection of acute myocardial ischemia, whereas, ØR changes can be used for prediction of its extent and severity.
authors.affiliation: Communications Technology Group (GTC) at the Aragón Institute for Engineering Research (I3A), Zaragoza, Spain. daromero@unizar.es
authors.forename: Daniel
authors.initials: D
authors.lastname: Romero
authors.forename: Michael
authors.initials: M
authors.lastname: Ringborn
authors.forename: Pablo
authors.initials: P
authors.lastname: Laguna
authors.forename: Esther
authors.initials: E
authors.lastname: Pueyo
mesh_terms: D000465:Algorithms; D054059:Coronary Occlusion / Q000150:complications / Q000175:diagnosis*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D006801:Humans; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000209:etiology; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity