title: ST-segment dynamics during reperfusion period and the size of myocardial injury in experimental myocardial infarction.
abstract: BACKGROUND
  Exacerbation of ST elevation associated with reperfusion has been reported in patients with myocardial infarction. However, the cause of the "reperfusion peak" and relation of its magnitude to the size of myocardial damage has not been explored. The aim of our study was to assess the correlation between the ST-dynamics during reperfusion, the myocardium at risk (MaR), and the infarct size (IS).
  
  
  METHODS
  Infarction was induced in 15 pigs by a 40-minute-long balloon inflation in the left anterior descending coronary artery. Tetrofosmin Tc 99m was given intravenously after 20 minutes of occlusion, and ex vivo single photon emission computed tomography was performed to assess MaR. Maximal ST elevation in a single lead and maximal sum of ST deviations in 12 leads were measured before, during, and after occlusion from continuous 12-lead electrocardiographic monitoring. A gadolinium-based contrast agent was given intravenously 30 minutes before explantation of the heart. Final IS was estimated using ex vivo cardiac magnetic resonance imaging.
  
  
  RESULTS
  All pigs developed an anteroseptal infarct with MaR = 42% ± 9% and IS = 26% ± 7% of left ventricle. In all pigs, reperfusion was accompanied by transitory exacerbation of ST elevation that measured 1300 ± 500 μV as maximum in a single lead compared with 570 ± 220 μV at the end of occlusion (P < .001). The transitory exacerbation of ST elevation exceeded the maximal ST elevation during occlusion (920 ± 420 μV, P < .05). The ST elevation resolved by the end of the reperfusion period (90 ± 30 μV, P < .001). Exacerbation of ST elevation after reperfusion correlated with the final IS (r = 0.64, P = .025 for maximal ST elevation in a single lead and r = 0.80, P = .002 for sum of ST deviations) but not with MaR (r = 0.43, P = .17 for maximal ST elevation in a single lead and r = 0.49, P = .11 for sum of ST deviations). The maximal ST elevation in a single lead and the sum of ST deviations during occlusion did not correlate with either MaR or final IS.
  
  
  CONCLUSIONS
  In the experiment, exacerbation of ST elevation is common during restoration of blood flow in the occluded coronary artery. The magnitude of the exacerbation of ST elevation after reperfusion in experimentally induced myocardial infarction in pigs is associated with infarct size but not with MaR.
authors.affiliation: Federal Centre of Heart, Blood and Endocrinology, Akkuratova 2, St. Petersburg, Russian Federation. marina.demidova@rambler.ru
authors.forename: Marina M
authors.initials: MM
authors.lastname: Demidova
authors.forename: Jesper
authors.initials: J
authors.lastname: van der Pals
authors.forename: Joey F A
authors.initials: JF
authors.lastname: Ubachs
authors.forename: Mikael
authors.initials: M
authors.lastname: Kanski
authors.forename: Henrik
authors.initials: H
authors.lastname: Engblom
authors.forename: David
authors.initials: D
authors.lastname: Erlinge
authors.forename: Victor M
authors.initials: VM
authors.lastname: Tichonenko
authors.forename: Pyotr G
authors.initials: PG
authors.lastname: Platonov
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004562:Electrocardiography / Q000379:methods*; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D009203:Myocardial Infarction / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery*; D015425:Myocardial Reperfusion / Q000379:methods*; D013552:Swine; D016896:Treatment Outcome