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Platelet activation during exercise-induced myocardial ischaemia
Insights
Platelet activation, measured by beta-thromboglobulin (beta-tg), is present at rest in patients with coronary artery disease. This activation correlates with disease extent but is not affected by exercise-induced ischemia.
Area of Science:
- Cardiology
- Hematology
- Clinical Medicine
Background:
- Platelet activation plays a role in atherothrombosis.
- Beta-thromboglobulin (beta-tg) is a marker of in vivo platelet activation.
Purpose of the Study:
- To investigate in vivo platelet activation in patients with ischemic heart disease.
- To determine the relationship between platelet activation, exercise, and coronary artery disease severity.
Main Methods:
- Maximal ECG treadmill exercise testing was performed on 26 normal subjects and 18 patients with ischemic heart disease.
- Plasma beta-thromboglobulin (beta-tg) levels were measured pre- and post-exercise.
- Coronary angiography was performed on 16 patients to assess coronary artery disease.
Main Results:
- Resting beta-tg levels were significantly higher in patients with ischemic heart disease compared to normal subjects (p < 0.05).
- Beta-tg levels did not change significantly after exercise in either group.
- Resting beta-tg levels positively correlated with the presence and extent of coronary artery disease (r = 0.53, p < 0.05).
- Post-exercise beta-tg levels showed no correlation with exercise-induced ischemia.
Conclusions:
- In vivo platelet activation is present at rest in patients with coronary artery disease.
- Resting platelet activation is related to the presence and extent of coronary artery disease.
- Exercise-induced ischemia does not appear to acutely affect in vivo platelet activation markers like beta-tg.
Abstract:
Twenty-six normal subjects (aged 18-52) and eighteen patients with ischaemic heart disease (aged 36-67) underwent maximal 12 lead ECG treadmill exercise testing. Coronary angiography was performed on sixteen of the patients. In-vivo platelet activation was assessed by measuring plasma levels of the platelet specific protein beta-thromboglobulin (beta-tg). The mean beta-tg levels pre- and post-exercise in the normal subjects were 47 (SD: 42- 26-85) ng/ml and 48 (29-78) ng/ml respectively, and in the patient group 68 (43-107) ng/ml and 70 (45-109) ng/ml. There was a significant difference between the two groups at rest (p less than 0.05), but there was no change in either following exercise. Post exercise beta-tg levels showed no correlation with the degree of induced ischaemia as judged by ST segment depression and the number of leads involved. Resting beta-tg levels, however, were positively correlated with the presence and extent of angiographically demonstrable coronary disease (r = 0.53, p less than 0.05). We conclude that in vivo platelet activation is present at rest in patients with coronary artery disease, and whilst related to the presence and extent of such disease is unrelated to induced ischaemia.