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Published on: April 6, 2017
Platelet aggregability in cardiac syndrome X
G A Lanza1, F Andreotti, A Sestito
1Istituto di Cardiologia, Università Cattolica del Sacro Cuore, Roma, Italy.
Insights
Platelet aggregability is higher at rest in cardiac syndrome X patients. Exercise reduces platelet aggregation in these patients, a response blocked by theophylline, indicating adenosine involvement.
Area of Science:
- Cardiology
- Hematology
- Exercise Physiology
Background:
- Cardiac Syndrome X presents with anginal chest pain and exercise-induced ST-segment depression despite normal coronary arteries.
- Platelet activation and aggregation play a role in cardiovascular diseases.
- Understanding platelet behavior in Syndrome X is crucial for diagnosis and treatment.
Purpose of the Study:
- To evaluate platelet aggregability at rest and during exercise in patients with cardiac Syndrome X.
- To compare platelet function in Syndrome X patients with those who have coronary artery disease and healthy individuals.
- To investigate the role of adenosine in exercise-induced platelet changes in Syndrome X.
Main Methods:
- A symptom-limited exercise test was conducted on 31 Syndrome X patients, 25 coronary artery disease patients, and 29 healthy subjects.
- Platelet aggregability was measured using a collagen/adenosine diphosphate coated ring in flowing whole blood at rest, peak exercise, and 30 and 120 minutes post-exercise.
- Adenosine antagonist (theophylline) was administered to a subset of patients to assess its effect on platelet aggregation.
Main Results:
- Syndrome X patients exhibited higher resting platelet aggregability compared to both coronary artery disease patients and healthy controls.
- Exercise led to decreased platelet aggregation in Syndrome X patients, unlike healthy controls where it remained unchanged.
- Theophylline administration abolished the exercise-induced reduction in platelet aggregation in Syndrome X patients, but not in healthy controls.
Conclusions:
- Patients with cardiac Syndrome X have increased platelet aggregability at rest.
- Exercise paradoxically reduces platelet aggregation in Syndrome X patients, suggesting a unique physiological response.
- The involvement of adenosine in this exercise-induced platelet modulation is strongly indicated by theophylline's inhibitory effect.
Aims:
To assess platelet aggregability at rest and in response to exercise in patients with cardiac syndrome X (anginal chest pain, ST-segment depression on exercise, angiographically normal coronary arteries).
Methods And Results:
We performed a symptom/sign-limited exercise test in 31 patients with syndrome X, 25 patients with coronary artery disease and 29 healthy subjects. Platelet aggregability was measured in flowing whole blood at baseline, at peak exercise, and after 30 and 120 min, as the time to occlude a collagen/adenosine diphosphate coated ring (aggregation time). Resting aggregation time was shorter in syndrome X patients (83.2+/-12 s), compared to patients with coronary disease (94.0+/-18 s, P<0.01) and to healthy subjects (96.4+/-21 s, P<0.01). With exercise, aggregation time did not change in healthy controls, decreased in patients with coronary disease (-13.8 s at peak; 95% CI, -10.2, -17.3 s;P<0.001), but increased in syndrome X (+17.4 s 30 min after exercise; 95% CI, +10.4, +24.4 s;P<0.0001). The intravenous administration of an adenosine antagonist (theophylline) prevented the exercise-induced prolongation of aggregation time in syndrome X patients (n=11), but had no effect in healthy controls (n=11).
Conclusion:
Platelet aggregability at rest was increased in syndrome X patients, compared to patients with coronary artery disease and healthy subjects. In contrast to patients with coronary disease, however, platelet aggregability was reduced by exercise. This response was prevented by theophylline, strongly suggesting the involvement of adenosine.
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