![]() ACUTE MYOCARDIAL ISCHEMIA AND THE ECG Acute myocardial ischemia may affect all components of the electrical activation of the heart, including the P wave, the PR interval, the QRS complex, the ST segment, and the T and U waves. On the other hand, most patients with incomplete occlusion of the coronary artery may be stabilized first with medical therapy before a decision is made to refer them for coronary angiography and revascularization. Obviously, patients with severe ischemia leading to ongoing myocardial necrosis should be rapidly diagnosed, as these patients may benefit from urgent reperfusion therapy (preferentially by primary percutaneous coronary intervention p‐PCI). This may occur even without formation of blood clots on ruptured atherosclerotic plaques. As mentioned above, ACS may be caused by abrupt increase of demand (tachyarrhythmia, sepsis, significant increase in afterload), usually in combination with limited ability to increase coronary flow (presence of fixed coronary narrowing due to preexisting coronary artery disease, vasoconstriction due to medication, hypotension, severe anemia, etc.). Dynamic changes in the size of the thrombus with distal embolization of platelet aggregates and clots and secretion of vasoactive substances lead to cyclic flow variations with repeat episodes of subendocardial ischemia (so‐called unstable angina) that may lead to myocardial cellular injury (acute myocardial infarction AMI). In many instances, the blood clot overlying the ruptured plaque does not completely block the blood flow. Occasionally, total occlusion of an epicardial coronary artery does not lead to transmural ischemia due to the presence of residual flow via collateral circulation. Other causes of an abrupt coronary artery occlusion are coronary embolus, spasm, and dissection of the aorta with involvement of the orifice of the main coronary artery or dissection of the coronary artery itself. This usually leads to complete or almost complete obliteration of the coronary artery lumen, resulting in acute transmural ischemia that involves all layers of the myocardium with necrosis of the involved tissue, if reperfusion does not occur rapidly. The most severe manifestation of ACS is acute reduction of blood flow, caused by an occlusive blood clot that is formed on a ruptured atherosclerotic plaque in an epicardial coronary artery. ECG Diagnosis and Classification of Acute Coronary Syndromes ECG Diagnosis and Classification of Acute Coronary Syndromesīirnbaum, Yochai Wilson, James Michael Fiol, Miquel Luna, Antonio Bayés Eskola, Markku Nikus, KjellĪcute coronary syndromes (ACS) are caused by an imbalance between myocardial oxygen demand and blood flow, which may be caused by either an acute reduction of blood supply or an increase in demand that cannot be matched by augmentation of blood flow. ![]()
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