Platelet aggregability in cardiac syndrome X.
OBJECTIVE
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).


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).


CONCLUSIONS
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.
Lanza
G A
GA
Istituto di Cardiologia, Università Cattolica del Sacro Cuore, Roma, Italy.
Andreotti
F
F
Sestito
A
A
Sciahbasi
A
A
Crea
F
F
Maseri
A
A
D000368:Aged; D003324:Coronary Artery Disease / Q000150:complications / Q000503:physiopathology; D015716:Electrocardiography, Ambulatory; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006400:Hematocrit; D006801:Humans; D008297:Male; D017566:Microvascular Angina / Q000150:complications / Q000503:physiopathology*; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D058915:Purinergic P1 Receptor Antagonists; D018047:Receptors, Purinergic P1 / Q000008:administration & dosage; D012146:Rest; D013806:Theophylline / Q000008:administration & dosage / Q000037:antagonists & inhibitors
D058915:Purinergic P1 Receptor Antagonists; D018047:Receptors, Purinergic P1; D013806:Theophylline