Circulating platelet/polymorphonuclear leukocyte mixed-cell aggregates in patients with mechanical heart valve replacement.

There is convincing evidence that cell adhesion plays an important role in cardiovascular pathology and is frequently associated to "in vivo" cellular activation. This study involves patients with mechanical heart valve replacement (MHVR patients) who have increased platelet polymorphonuclear leukocyte (PMN) reactivity. Dual-color cytometry was used to determine the expression of adhesive molecules on cellular surfaces, platelet, and PMN-bound fibrinogen as well as the presence of circulating platelet/PMN mixed-cell aggregates (MCA) in 55 MHVR patients, 49 control patients under oral anticoagulant therapy, and 22 healthy volunteers. The results demonstrated that (a) PMN from MHVR patients showed an increased PMN-bound fibrinogen (mean +/- SEM: 1,420 +/- 169 anti-fibrinogen fluorescence intensity, P= 0.0012), when compared to controls (mean +/- SEM: 747 +/- 32 anti-fibrinogen fluorescence intensity) and healthy volunteers (mean +/- SEM: 692 +/- 25 anti-fibrinogen fluorescence intensity; (b) platelet activation in MHVR patients was evidenced by the higher expression of CD62P (mean +/- SEM: 128 +/- 19 anti-CD62P fluorescence intensity, P = 0.003) compared to controls (mean +/- SEM: 65 +/- 15 and 50 +/- 10 anti CD62P fluorescence intensity) and by increased levels of platelet-bound fibrinogen (mean +/- SEM: 625 +/- 20 anti-fibrinogen fluorescence intensity, P = 0.0043 versus 496 +/- 45 and 480 +/- 30 for control patients and for healthy volunteers, respectively); and (c) the proportion of MCA in MHVR patients (15 +/- 2%) was significantly higher (P = 0.009) compared to controls (7 + 1%) and healthy volunteers (6 +/- 2%). The results indicate that the presence of stable circulating MCA represents another marker of "in vivo" PMN activation in MHVR patients.