Comparison of platelet activation in unstable and stable angina pectoris and correlation with coronary angiographic findings

We sought to investigate the relation between platelet activation and the a ngiographic evidence of ruptured plaque in patients presenting with unstabl e and stable angina pectoris. We prospectively enrolled 25 consecutive pati ents (5 women and 20 men, mean age 62 +/- 3 years), 17 with unstable angina and 8 with stable angina. Systemic venous blood samples were! collected wi thin 4 to 6 hours of admission for flow cytometry analysis. Activation-depe ndent epitope CD63 and glycoprotein IIb/IIIa on the platelet membrane were assayed. Fibrinogen levels were also measured. All patients with unstable a ngina underwent cardiac catheterization and had angiographic evidence of ru ptured plaque. Of the patients with stable angina, 5 underwent coronary ang iography with smooth noncomplex lesions and 3 had negative technetium-99m s estamibi stress tests. Patients with unstable angina were characterized by 39% higher levels of fibrinogen than patients with stable angina (423 +/- 3 04 vs 304 +/- 51 mg/dl, p = 0.004). The percentage of platelets positive fo r the activation-dependent epitope CD63 was 5 times higher in patients with unstable than stable angina (14.6 +/- 5.6% vs 2.75 +/- 1.6%, p = 0.0026). They also had a 15% higher expression of their glycoprotein IIb/IIIa (517 /- 79 vs 449 +/- 50 mean fluorescence intensity, p = 0.038). Thus, this stu dy establishes a direct relation between the morphology of ruptured plaque and platelet activation in patients with unstable angina. This may allow fo r further risk stratification. Patients with unstable complex lesions had a fivefold higher expression of the platelet activation epitope CD63 than pa tients with stable angina. Furthermore, they had 15% more glycoprotein IIb/ IIIa aggregation sites expressed on their platelet membrane, thus indicatin g an intense thrombogenic potential. (C) 2000 by Excerpta Medica, Inc.