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[Myocardial infarct of effort with normal coronaries. Study of in vivo platelet activation]
Insights
Platelet activation increases during exercise in patients with myocardial infarction, even without coronary artery disease. This suggests platelets play a role in heart attacks, independent of blocked arteries.
Area of Science:
- Cardiology
- Hematology
- Exercise Physiology
Context:
- Myocardial infarction (MI) with normal coronary arteries is a recognized clinical entity.
- The role of platelet activation in MI pathogenesis remains incompletely understood.
- Exercise stress testing is a common diagnostic tool for evaluating cardiovascular health.
Purpose:
- To investigate platelet activation during ergometric stress testing in patients with MI and normal coronary arteries.
- To compare platelet morphology and specific platelet proteins in patients with MI (with and without coronary insufficiency) and healthy controls.
- To determine if exercise-induced platelet activation correlates with myocardial ischemia.
Summary:
- Platelet morphology and plasma concentrations of platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG) were assessed at rest, peak exercise, and recovery.
- A significant increase in morphologically modified platelets was observed at peak exercise in patients with MI (Groups A and B), but not in healthy subjects (Group C).
- This exercise-induced platelet activation occurred independently of myocardial ischemia, as evidenced by findings in patients with negative maximal exercise stress tests.
Impact:
- Suggests that platelet activation may contribute to myocardial infarction, even in the absence of significant coronary artery disease.
- Highlights the potential role of platelets in the pathophysiology of MI with normal coronary arteries.
- Provides insights into the physiological responses of platelets during exercise in cardiovascular disease.
Abstract:
Platelet activation may play a part in causing myocardium infarction with angiographically normal coronary arteries. We investigated this possibility by performing ergometric stress testing in a series of 9 patients (Group A) who had suffered myocardial infarction after a violent effort with angiographically documented coronary insufficiency responsible for a stable effort angina (Group B) and 11 healthy subjects (Group C). Blood samples were taken separately before exercise, at the peak of exercise, and during the recovery period. Platelet morphology, a sensitive indication of the degree of platelet activation, was studied by phase contrast microscopy after immediate fixation of the blood. The percentage of non-discoidal platelets presenting with one or several spicules was measured. At the same time, the plasma concentrations of platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG) were measured. At rest, there was no difference in platelet morphology or specific platelet proteins between the 3 groups. At the peak effort, there was a significant increase of the number of morphologically modified platelets in Groups A and B but not in healthy subjects. This platelet activation could not be linked to the presence of myocardial ischaemia because it was found both in patients with a negative maximal exercise stress test (Group A). Finally, no increase of the plasma concentrations of the platelet protein was observed in any of the groups.