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Platelet aggregation and thromboxane B2 release in patients with acute myocardial infarction--their relation to
1Department of Internal Medicine, Faculty of Medicine, Kyoto University, Japan.
Insights
Platelet aggregation and thromboxane B2 production decrease in acute myocardial infarction patients with occluded infarct vessels. Vessel patency influences these platelet function changes, impacting treatment evaluation.
Area of Science:
- Cardiology
- Hematology
- Biochemistry
Background:
- Platelet function is crucial in acute myocardial infarction (AMI).
- Intracoronary thrombolysis aims to restore blood flow.
- The impact of infarct vessel patency on platelet function during AMI is not fully understood.
Purpose of the Study:
- To evaluate platelet function in the aortic blood of AMI patients undergoing urokinase thrombolysis.
- To compare platelet function based on infarct vessel patency in the acute phase and after treatment.
Main Methods:
- Assessed platelet aggregation (induced by adenosine diphosphate and arachidonic acid) and serum thromboxane B2 production.
- Measured plasma thromboxane B2 levels in the aorta and great cardiac vein.
- Classified 39 patients into two groups based on coronary arteriography: completely occluded (Group 1) vs. patent infarct vessel (Group 2).
Main Results:
- In the acute stage, Group 1 (occluded vessel) showed decreased platelet aggregation and serum thromboxane B2 compared to Group 2 (patent vessel).
- Platelet aggregation increased in Group 1 after 4 weeks, normalizing to levels similar to Group 2 and controls.
- Plasma thromboxane B2 was elevated in the aorta acutely, likely from infarct vessel washout, and normalized after 4 weeks.
Conclusions:
- Platelet aggregation and serum thromboxane B2 production are relatively decreased in AMI patients with totally occluded infarct vessels, despite elevated plasma thromboxane B2.
- Infarct vessel patency is a critical factor to consider when assessing platelet function in acute myocardial infarction.
Abstract:
Platelet function in the aortic blood in 39 patients who underwent intracoronary thrombolysis with urokinase was evaluated in the acute stage of myocardial infarction and after 4 weeks. The patients were classified into 2 groups according to the patency of the infarct vessel shown by coronary arteriography before urokinase administration. In the acute stage, 26 patients with completely occluded infarct vessel (group 1) showed a decreased level of platelet aggregation induced by adenosine diphosphate or arachidonic acid as compared with 13 patients with patent infarct vessel (group 2). The platelet aggregation in group 1 increased 4 weeks later and both groups showed similarly enhanced platelet aggregation levels as compared with normal controls. Like platelet aggregation, serum thromboxane B2 production in group 1 was lower than that in group 2 in the acute stage. Plasma thromboxane B2 levels in the aorta in both groups were significantly elevated in the acute stage, and were normalized after 4 weeks. This elevation of thromboxane B2 seems to be due to its washout from the infarct vessel, because plasma thromboxane B2 levels were significantly higher in the great cardiac vein than those in the aorta after successful reperfusion in group 1 or group 2. In conclusion, despite a significant elevation in plasma thromboxane B2 levels, platelet aggregation and serum thromboxane B2 production relatively decrease in patients with totally occluded infarct vessel. The patency of the infarct vessels should be taken into account when evaluating platelet function in acute myocardial infarction.