Copyright © 2001 by the European Society of Cardiology.
Platelet aggregability in cardiac syndrome X
Istituto di Cardiologia, Università Cattolica del Sacro Cuore, Roma, Italy
revised January 23, 2001; accepted January 24, 2001
Abstract
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 120min, as the time to occlude a collagen/adenosine diphosphate coated ring (aggregation time). Resting aggregation time was shorter in syndrome X patients (83·2±12s), compared to patients with coronary disease (94·0±18s, P<0·01) and to healthy subjects (96·4±21s, P<0·01). With exercise, aggregation time did not change in healthy controls, decreased in patients with coronary disease (–13·8s at peak; 95% CI, –10·2, –17·3s;P<0·001), but increased in syndrome X (+17·4s 30min after exercise; 95% CI, +10·4, +24·4s;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.
Key Words: Syndrome X, platelet aggregability, exercise, adenosine
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