Platelet aggregability in cardiac syndrome X.

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.