title: Quantification of myocardium at risk and detection of reperfusion by dynamic vectorcardiographic ST segment monitoring in a pig occlusion-reperfusion model.
abstract: OBJECTIVE
  The aim was to investigate whether continuous computerized vectorcardiographic monitoring of absolute spatial ST vector magnitude (ST-VM) and spatial ST change vector magnitude (STC-VM) during coronary occlusion could be used to estimate the size of myocardium at risk; and also to test whether reperfusion could be distinguished from sustained occlusion by continuous monitoring of ST vector alterations.
  
  
  METHODS
  Computerised vectorcardiographic monitoring via Frank leads was applied in a closed chest occlusion-reperfusion pig model. Coronary occlusion over 24 h was produced in 20 animals by injecting a 2 mm ball into the left anterior descending coronary artery (n = 7), the right coronary artery (n = 8), and the left circumflex coronary artery (n = 5). Another 31 pigs were reperfused by retraction of the ball after 30 (n = 10), 60 (n = 15), or 90 (n = 6) min of left anterior descending artery occlusion. The extent of the myocardium at risk was measured by autoradiography.
  
  
  RESULTS
  Seven animals were excluded. Irrespective of occluded coronary artery the relative parameters STC-VM over the first 30 min of occlusion correlated closely with area at risk, that is, the mean STC-VM between 10 and 30 min of occlusion (r = 0.78 p < 0.001). The absolute parameter ST vector magnitude (ST-VM) did not reflect ischaemia in 16/44 animals and did not correlate significantly with area at risk. The weight of myocardium at risk (MAR) was predictable from STC-VM: MAR weight (measured) = 0.97 x MAR weight (predicted) + 0.26 (g), r = 0.81, p < 0.001. STC-VM decline rate, time to STC-VM plateau, and cumulated sum plots of STC-VM were all able to distinguish reliably between reperfused animals and those with permanent occlusion. A paradoxical increase in STC-VM - "reperfusion peak" - was detected in 17/31 (55%) of the animals. This phenomenon was related to large amount of myocardium at risk or to a long occlusion time.
  
  
  CONCLUSIONS
  Dynamic vectorcardiographic ST monitoring provides adequate estimation of myocardium at risk and enables detection of reperfusion in experimental myocardial ischaemia.
authors.affiliation: Department of Medicine, University Hospital, Umeå, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Näslund
authors.forename: S
authors.initials: S
authors.lastname: Häggmark
authors.forename: G
authors.initials: G
authors.lastname: Johansson
authors.forename: S
authors.initials: S
authors.lastname: Reiz
mesh_terms: D000818:Animals; D001345:Autoradiography; D004195:Disease Models, Animal; D001330:Electronic Data Processing; D006321:Heart / Q000503:physiopathology; D017202:Myocardial Ischemia / Q000473:pathology* / Q000503:physiopathology; D015428:Myocardial Reperfusion Injury / Q000473:pathology* / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology*; D009929:Organ Size / Q000502:physiology; D012306:Risk; D013552:Swine; D014672:Vectorcardiography