Myocardial cellular alterations during myocardial ischemia and evolving infarction.
Primary decreases in oxygen delivery to the myocardium associated with important reductions in coronary blood flow are the main mechanism of myocardial necrosis. Endothelial injury at sites of coronary artery stenosis, platelet attachment, and release of humoral mediators, including thromboxane A2 and serotonin, may be major causes of primary reductions in coronary blood flow leading to unstable angina and acute myocardial infarction (MI). Findings of clinical studies are consistent with the hypothesis that platelet aggregation and subsequent increases in thromboxane and serotonin concentrations may play a role in causing acute MI, death, or both in patients with unstable angina. Animal studies suggest that both thromboxane and serotonin are important in initiating or sustaining the cyclic coronary blood flow reductions that occur after severe stenosis and endothelial injury. If the contribution from either of these humoral mediators is eliminated or antagonized, cyclic flow reductions are usually terminated. Beta blocker and/or thrombolytic therapy administered within the first two hours after onset of coronary artery occlusion may limit infarct size and improve segmental ventricular function. When given within six hours of symptoms of MI, thrombolytic therapy may reduce mortality.
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000818:Animals; D003326:Coronary Circulation; D003327:Coronary Disease / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology*; D004285:Dogs; D005343:Fibrinolytic Agents / Q000627:therapeutic use; D006801:Humans; D009203:Myocardial Infarction / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology*; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption; D010974:Platelet Aggregation; D012701:Serotonin / Q000502:physiology*; D013928:Thromboxane A2 / Q000502:physiology*; D014655:Vascular Resistance
D000319:Adrenergic beta-Antagonists; D005343:Fibrinolytic Agents; D012701:Serotonin; D013928:Thromboxane A2