Acute myocardial infarction: Difference between revisions
(Created page with "'''Acute myocardial infarction''' (AMI), sometimes called a '''heart attack''', is a life-threatening condition caused by ischaemia of the myocardium. == Pathomechanism == AMI occurs when a coronary atherosclerotic plaque ruptures, exposing the highly thrombogenic subendothelial matrix of the plaque to the blood. The coagulation system is activated, resulting in a thrombus growing on the ruptured plaque and obstructing the blood flow. When the...") |
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Revision as of 11:08, 19 October 2023
Acute myocardial infarction (AMI), sometimes called a heart attack, is a life-threatening condition caused by ischaemia of the myocardium.
Pathomechanism
AMI occurs when a coronary atherosclerotic plaque ruptures, exposing the highly thrombogenic subendothelial matrix of the plaque to the blood. The coagulation system is activated, resulting in a thrombus growing on the ruptured plaque and obstructing the blood flow.
When the occlusion is complete (100% of the lumen), the occlusion causes a transmural infarction (necrosis) of the myocardium in the area supplied by the occluded vessel. Clinically, this causes ST-elevation myocardial infarction.
When the occlusion is partial, a subendocardial infarction occurs. Clinically, this causes non-ST elevation coronary syndrome.
Type 2 infarction
The process described above refers to the most common type of infarction, the so-called type 1 infarct. Other types of infarcts also exist, most notably type 2 infarcts. In type 2 infarcts there is an increased oxygen demand and/or decreased oxygen supply to the myocardium which is not due to coronary artery thrombosis. This can be due to coronary artery spasm, embolus, tachyarrhythmias, anaemia, respiratory failure, hypertension, hypotension, etc. Up to 28% of patients with myocardial infarction don’t have significant coronary artery disease and so their underlying cause must be something else, presumably a type 2 infarction.