Increased platelet reactivity in unstable angina patients is not related to C-reactive protein levels

Platelets are a major component of thrombi, and coronary thrombosis plays a key role in the pathogenesis of unstable angina (UA). Whether platelet aggregability is increased in UA patients however, is not known. Furthermore, no study has investigated the relationship between platelet reactivity and inflammation in UA patients In this study, venous blood samples were collected at admission in coronary care unit in 37 patients with unstable angina (Braunwald class IIIB) and in 37 sex- and age-matched patients with chronic stable angina (CSA). Patients taking thienopyridine or anticoagulant drugs were excluded from the study, as also were excluded patients with a history of acute myocardial infarction in the previous 12 months. Platelet aggregability was measured on flowing blood as time to occlude a ring coated with collagen-adenosine diphosphate (ADP), using the platelet function analyzer (PFA-100) system. By this method, the time to occlusion (closure time) is taken as a measure of platelet adhesion/aggregability, with shorter times indicating greater platelet reactivity. There were 23 men and 14 women in both groups, and age was 67.7 +/- 8 and 67.5 +/- 8 years in UA and SA, respectively (P = 0.93). Closure time was significantly reduced in UA patients (78.8 +/- 14 s), compared to SA patients (93.3 +/- 19 s, P < 0.001). Among UA patients, serum C-reactive protein (CRP) levels had a median value of 5.1 mg/l (bottom and top quartile levels, 1.50-7.95). There was no significant correlation between closure time and CRP levels (r = 0.22, P = 0.29). Our data show that, in patients with unstable angina there is an increase of platelet reactivity in response to ADP/collagen stimulation, which is not related to inflammation.