title: Dynamic mechanisms of cardiac oxygenation during brief ischemia and reperfusion.
abstract: Myocardial oxygenation may be altered markedly by changes in tissue blood flow. During brief ischemia and reperfusion produced by transient occlusion of the left anterior descending artery in 10 open-chest dogs, changes in the oxygenation of tissue hemoglobin (Hb) plus myoglobin (Mb) and the oxidation-reduction (redox) state of mitochondrial cytochrome aa3 were monitored continuously using near-infrared spectroscopy. The nondestructive optical technique indicated that coronary occlusion produced an abrupt drop in tissue oxygen stores (tHb02 + Mb02), tissue blood volume (tBV), and the oxidation level of cytochrome aa3. Changes in the cytochrome oxidation state were related inversely to transmural collateral blood flow within the ischemic region (r = 0.77) measured with radiolabeled microspheres. Furthermore, there was a direct relationship (r = 0.91) between collateral blood flow and the tissue level of desaturated Hb and Mb (tHb + Mb). Reperfusion after 2 min of ischemia led to a synchronous overshoot of baseline in coronary flow and tBV followed by supranormal increases in tHb + Mb02 and the oxidation level of cytochrome aa3. The tHb + Mb level increased transiently during reperfusion. This response correlated inversely with collateral flow during ischemia (r = 0.91). Accordingly, the time required to reach peak tHb + Mb levels was shortest in dogs with high collateral flows (r = 0.75). Thus collateral blood flow partially sustains myocardial oxygenation during coronary artery occlusion and influences tissue reoxygenation early during reperfusion.
authors.affiliation: Department of Medicine, Duke University, Durham 27710.
authors.forename: W J
authors.initials: WJ
authors.lastname: Parsons
authors.forename: J C
authors.initials: JC
authors.lastname: Rembert
authors.forename: R P
authors.initials: RP
authors.lastname: Bauman
authors.forename: J C
authors.initials: JC
authors.lastname: Greenfield
authors.forename: C A
authors.initials: CA
authors.lastname: Piantadosi
mesh_terms: D000818:Animals; D003097:Collateral Circulation; D003326:Coronary Circulation; D003327:Coronary Disease / Q000378:metabolism* / Q000503:physiopathology; D004285:Dogs; D003576:Electron Transport Complex IV / Q000378:metabolism; D006454:Hemoglobins / Q000032:analysis; D007259:Infrared Rays; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000378:metabolism*; D009211:Myoglobin / Q000032:analysis; D010101:Oxygen Consumption
chemical_list: D006454:Hemoglobins; D009211:Myoglobin; D003576:Electron Transport Complex IV