Inverse relationships between coronary blood flow obstruction and platelet reactivity in stable angina pectoris

This study investigates relationships between platelet reactivity and coronary blood flow obstruction in stable angina pectoris. Consented were 36 patients with single-vessel disease. The subjects were divided into two groups. One group (n=14) had less severe (<=80%) and the second group (n=22) had severe coronary flow impairment (90%). Before elective coronary angiography platelet in vitro reactivity in venous whole blood was determined using a flow cytometry technique. A thrombin-receptor activating peptide (TRAP-6) (0.77 and 0.06 g/l) and ADP (8.5 and 1.7 micromol/l) were used to activate platelets. The number of fibrinogen positive cells (%) i.e., activated platelets after stimulation was employed as experimental parameter. Less severe flow obstruction was associated with more reactive platelets. When stimulating with 0.77 g/l TRAP-6 the number of activated platelets was 64+/-15 (SD)%. The corresponding value for the group with severe flow obstruction was 40+/-17(SD)%. The difference is significant (P<0.001). 0.06 g/l TRAP-6 yielded similar results (P<0.01). Also when using 8.5 micromol/l ADP to challenge platelets less severe flow obstruction was associated with enhanced reactivity (P<0.01). 1.7 micromol/l ADP generated comparable results (P<0.05). Thus, in stable angina pectoris coronary flow obstruction is inversely related to platelet reactivity.