title: Intracoronary ECG during primary percutaneous coronary intervention for ST-segment elevation myocardial infarction predicts microvascular obstruction and infarct size.
abstract: BACKGROUND
  Microvascular obstruction (MVO) following ST-segment elevation myocardial infarction (STEMI) is associated with larger infarct size and an increased mortality. Although angiographic predictors of MVO in primary percutaneous coronary intervention (primary-PCI) setting have been identified, an earlier and objective "in-lab" predictor may be beneficial, in order to potentially influence therapies administered during primary-PCI. We hypothesised that intracoronary-electrocardiogram (IC-ECG) is a simple, objective and accurate predictor of MVO evaluated by cardiac magnetic resonance (CMR) and is comparable to myocardial blush grade (MBG) and TIMI myocardial perfusion grade (TMPG).
  
  
  METHODS
  Intracoronary ECG was performed during primary-PCI. Intracoronary ST-segment measurement was performed before and immediately after opening of infarct-related-artery. Intracoronary ST-segment resolution (IC-STR) was defined as ≥ 1 mm improvement compared to baseline. Contrast enhanced CMR was performed at 4 and 90 days post primary-PCI. Primary endpoint was MVO on late gadolinium hyperenhancement assessed by CMR at day 4.
  
  
  RESULTS
  Sixty-four consecutive patients (age 59 ± 11 years; 55 males) were recruited. Intracoronary ST-segment resolution correlated with MVO (p=0.005). Furthermore, IC-STR correlated with infarct-mass, non-viable-mass, peak creatinine kinase and end-systolic-volume at day 4. Intracoronary ST-segment resolution also correlated with favourable left ventricular end-diastolic-volume at day 90 (p=0.022). On multivariate analysis, IC-STR was an independent predictor of MVO.
  
  
  CONCLUSIONS
  Intracoronary ST-segment resolution is a strong in-lab predictor of MVO assessed 4 days after STEMI on CMR. Furthermore, IC-STR correlates with infarct size and left ventricular remodelling at 3 months. Further studies are required to understand potential clinical utility of this tool.
authors.affiliation: Cardiovascular Research Centre, Royal Adelaide Hospital & Discipline of Medicine, University of Adelaide, Adelaide, Australia.
authors.forename: Dennis T L
authors.initials: DT
authors.lastname: Wong
authors.forename: Michael C H
authors.initials: MC
authors.lastname: Leung
authors.forename: Rajiv
authors.initials: R
authors.lastname: Das
authors.forename: Gary Y H
authors.initials: GY
authors.lastname: Liew
authors.forename: Karen S L
authors.initials: KS
authors.lastname: Teo
authors.forename: Derek P
authors.initials: DP
authors.lastname: Chew
authors.forename: Ian T
authors.initials: IT
authors.lastname: Meredith
authors.forename: Matthew I
authors.initials: MI
authors.lastname: Worthley
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Worthley
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003331:Coronary Vessels / Q000473:pathology* / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D062645:Percutaneous Coronary Intervention / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016896:Treatment Outcome