Fluorescence spectroscopic analysis of circulating platelet activation during coronary angioplasty

Background and Objective: Platelet activation during percutaneous transluminal coronary angioplasty (PTCA) initiates thrombus formation and plaque regrowth at sites of arterial injury, limiting procedure efficacy. We have developed a simple assay for circulating platelet activation based on fluorescence analysis of membrane fluidity and intracellular calcium concentration and light scattering analysis of platelet aggregation. Study Design/Materials and Methods: Platelet activation state was measured in 45 patients undergoing angioplasty, before and after treatment with platelet inhibitors. Results: PTCA alone produced a decrease in pyrene dimer formation (P ≤ 0.0083) and an increase in light scattering at 650 nm (P ≤ 0.0128). Treatment with ADP and GPIIb/IIIa receptor antagonists reduced PTCA induced changes in pyrene dimer formation. An unexpected decrease in pyrene dimer formation (P ≤ 0.05) was detected when the GPIIb/IIIa receptor antagonist was given together with an ADP receptor antagonist. Conclusions: 1) Analysis of membrane fluidity provides a sensitive marker for platelet activation state. 2) Reduced membrane fluidity after combined platelet inhibitor treatments suggests reduced antiplatelet efficacy.