Ticlopidine and aspirin fail to suppress the increased platelet aggregability that follows percutaneous coronary interventions

Previous studies indicate that percutaneous transluminal coronary angioplasty (PTCA) is associated with platelet activation. It is not well-established whether enhanced platelet aggregability after PTCA is prevented by the association of ticlopidine with aspirin. The aim of this study was to evaluate whole blood platelet aggregability before and after elective PTCA in patients with chronic stable angina receiving ticlopidine and aspirin. We studied 16 patients referred for elective PTCA, treated for ≥ 72 hours with oral aspirin and ticlopidine (group 1), and 10 patients referred for diagnostic coronary angiography, treated with oral aspirin alone (group 2). An intravenous bolus of heparin was administered at the start of PTCA. In both groups, platelet aggregability was assessed at baseline and 24 hours after the procedure, using the PFA 100® system. This method measures the time required for flowing whole blood to occlude a collagen and adenosine diphosphate (ADP)-coated ring, shorter times indicating greater aggregability. In both groups, platelet aggregability after the procedure was significantly increased compared with baseline: 104±30 seconds before versus 88±24 seconds at 24 hours in group 1 (p=0.03) and 84±16 seconds before versus 69± 14 seconds at 24hours in group 2 (p=0.004). Group 1 patients, compared with group 2, showed a trend toward reduced aggregability at baseline (p=0.06) and significantly lower aggregability 24 hours after the procedure (p=0.03). Ticlopidine and aspirin reduce whole-blood platelet aggregability compared with aspirin alone but fail to suppress the increased aggregability that occurs 24 hours after PTCA.