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 angiographic evidence of ruptured plaque in patients presenting with unstable and stable angina pectoris. We prospectively enrolled 25 consecutive patients (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 within 4 to 6 hours of admission for flow cytometry analysis. Activation-dependent epitope CD63 and glycoprotein IIb/IIIa on the platelet membrane were assayed. Fibrinogen levels were also measured. All patients with unstable angina underwent cardiac catheterization and had angiographic evidence of ruptured plaque. Of the patients with stable angina, 5 underwent coronary angiography with smooth noncomplex lesions and 3 had negative technetium-99m sestamibi stress tests. Patients with unstable angina were characterized by 39% higher levels of fibrinogen than patients with stable angina (423 +/- 304 vs 304 +/- 51 mg/dl, p = 0.004). The percentage of platelets positive for 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 study establishes a direct relation between the morphology of ruptured plaque and platelet activation in patients with unstable angina. This may allow for further risk stratification. Patients with unstable complex lesions had a fivefold higher expression of the platelet activation epitope CD63 than patients with stable angina. Furthermore, they had 15% more glycoprotein IIb/IIIa aggregation sites expressed on their platelet membrane, thus indicating an intense thrombogenic potential.