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Dynamic intracoronary thrombosis does not cause significant downstream platelet embolization
J A Barrabés1, D Garcia-Dorado, B Soriano
1Servicio de Cardiología, Hospital General Universitari Vall d'Hebron, Barcelona, Spain.
Insights
Mural intracoronary thrombi cause minimal platelet embolization to downstream myocardium, even with repeated occlusions. Aspirin did not reduce this platelet accumulation, suggesting limited therapeutic benefit for this specific complication.
Area of Science:
- Cardiovascular Research
- Thrombosis and Hemostasis
- Experimental Medicine
Background:
- Mural intracoronary thrombi can release platelet emboli, potentially obstructing microvessels.
- The extent of myocardial platelet accumulation from such thrombi and its modulation by interventions remain poorly characterized.
Purpose of the Study:
- To quantify myocardial platelet accumulation downstream of a mural intracoronary thrombus.
- To investigate the impact of transient coronary occlusion and aspirin treatment on this accumulation.
Main Methods:
- Utilized 99mTc-labeled platelets to assess myocardial platelet content in pigs with induced left anterior descending coronary artery (LAD) thrombosis.
- Compared groups with no intervention, transient coronary occlusion (OC), and OC with aspirin pre-treatment.
Main Results:
- Transient coronary occlusion significantly increased myocardial platelet content in the LAD region.
- Aspirin pre-treatment reduced cyclic flow reductions but did not decrease LAD myocardial platelet accumulation.
- Myocardial platelet accumulation correlated with myeloperoxidase activity and infarct size, not directly with thrombus burden or emboli.
Conclusions:
- Platelet embolization from mural intracoronary thrombi into downstream myocardium is minimal, despite dynamic thrombosis.
- Current findings suggest limited efficacy of aspirin in preventing microvascular platelet accumulation in this model.
Objective:
A mural intracoronary thrombus is a potential source of platelet emboli that may obstruct downstream microvessels, but this phenomenon has not been characterized. The present study aimed to assess the magnitude of myocardial platelet accumulation downstream of a mural intracoronary thrombus and its modification by a concomitant transient coronary occlusion (OC) or by treatment with aspirin.
Methods:
The myocardial content of 99mTc-labelled platelets was analyzed in 26 pigs submitted to intimal injury of the left anterior descending coronary artery (LAD) followed by no intervention (n=6), 25-min OC (n=6), or 48-min OC preceded (n=8) or not (n=6) by intravenous administration of 250 mg aspirin.
Results:
After 2 h, 24 animals had had 12+/-1 cyclic flow reductions (CFRs) reflecting dynamic LAD thrombosis. Myocardial platelet content in the inferior region was similar among groups. Platelet content in the LAD region was not significantly different to that in the inferior region (129+/-19%, P=NS) in the no intervention group, but was increased following OC (172+/-20 and 312+/-71% after 25- and 48-min OC, respectively, P<0.05). Pre-treatment with aspirin lessened the number of CFRs but did not reduce platelet accumulation in LAD myocardium (483+/-148%). Myocardial platelet accumulation was not associated with the magnitude of platelet deposition in the LAD nor with the number of CFRs, but was correlated with myeloperoxidase activity (r=0.91, P<0.001) and with infarct size (r=0.52, P=0.05). Histological analysis frequently showed sparse platelets or small platelet or leukoplatelet aggregates in small vessels, but arteriolar emboli were rare. In none of seven additional experiments coronary angiography showed obstructions of arterial branches during CFRs.
Conclusion:
The magnitude of platelet embolization from a mural intracoronary thrombus into downstream myocardium is small despite the presence of repetitive CFRs.