Platelet aggregability in vivo is attenuated byverapamil but not bymetoprolol in patients with stable angina pectoris

The effects of 1 month of treatment with either verapamil or metoprolol on several aspects of platelet function were studied at rest and during physical exercise or mental stress in patients with stable angina pectoris participating in the Angina Prognosis Study in Stockholm. Platelet aggregability was measured by filtragometry ex vivo, which reflects platelet aggregability in vivo and by Born aggregometry in vitro. Platelet secretion in vivo was assessed by measurements of β-thromboglobulin in plasma. Verapamil reduced plasma norepinephrine levels (from 2.6 ± 1.0 to 2.2 ± 1.0 nmol/L; p <0.01) and attenuated platelet aggregability at rest (filtragometry readings were prolonged from 219 to 295 seconds; p <0.05, n = 46). A gregability in platelet-rich plasma was not influence Metoprolol did not significantly affect filtragometry readings (n = 58) or aggregability in vitro (there was a tendency toward enhanced adenosine diphosphate sensitivity; p = 0.08). β-thromboglobulin levels were low (≈25 ng/ml) and not influenced by either treatment. Physical exercise (bicycle ergometry) increased platelet aggregability in vivo both before and after drug treatment. Verapamil also attenuated platelet aggregability after exercise, whereas metoprolol had no such effect. Platelet function was not seriously altered by mental stress (Stroopʹs color word test) despite significant effects on hemodynamics and plasma catecholamines either before or after treatment with either drug. Thus, verapamil attenuates platelet aggregabiliy in patients with stable angina pectoris, whereas metoprolol has no such effect.