title: Lack of sensitivity of the electrocardiogram for detection of old myocardial infarction: a cardiac magnetic resonance imaging study.
abstract: BACKGROUND
  The presence of Q waves in the electrocardiogram (ECG) has been used as a marker of prior myocardial infarction (MI). Its accuracy, however, is uncertain. The purpose of this study is to determine the accuracy of an ECG to detect prior MI compared with a novel criterion standard.
  
  
  METHODS
  This study conducted retrospective inclusion with de novo analysis of ECG and cardiac magnetic resonance (CMR) by independent blinded readers in a single-institution setting. The population consisted of a consecutive sample of 146 patients referred for CMR for evaluation of myocardial viability and necrosis. Q/QS waves on ECG were defined as per Minnesota Code criteria. Myocardial scar was quantified and localized by CMR delayed contrast hyperenhancement and assumed as criterion standard. Sensitivity, specificity, and predictive values of ECG were calculated for different scar sizes (>1%, >15%, and >30% of the myocardium) and location (global, anterior, inferior, and lateral walls).
  
  
  RESULTS
  Sensitivity was 48.4%; specificity, 83.5; positive predictive accuracy, 72.0%; and negative predictive accuracy, 64.2%. Sensitivity improved when only large infarcts were considered (64.2%), but specificity decreased to 72.7%. Sensitivity for detecting isolated anterior or inferior wall scars was similar, but isolated lateral wall scar was rarely identified (14.3%). When all 3 walls were involved, sensitivity was still low at 57.9%.
  
  
  CONCLUSIONS
  The lack of sensitivity and the resulting low negative predictive value of Q/QS criteria seriously limit its accuracy as a marker of prior MI.
authors.affiliation: Section of Cardiology, Department of Internal Medicine, Washington Hospital Center, Washington, DC, USA.
authors.forename: Federico M
authors.initials: FM
authors.lastname: Asch
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Shah
authors.forename: Christine
authors.initials: C
authors.lastname: Rattin
authors.forename: Srirama
authors.initials: S
authors.lastname: Swaminathan
authors.forename: Anthon
authors.initials: A
authors.lastname: Fuisz
authors.forename: Joseph
authors.initials: J
authors.lastname: Lindsay
mesh_terms: D000368:Aged; D002921:Cicatrix / Q000175:diagnosis / Q000209:etiology; D017352:Echo-Planar Imaging; D004562:Electrocardiography / Q000592:standards; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000175:diagnosis*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016037:Single-Blind Method