Elevated platelet microparticles in transient ischemic attacks, lacunar infarcts, and multiinfarct dementias.

Platelets release microparticles (PMP) upon activation. Elevated levels of PMP were observed in patients with immune thrombocytopenic purpura (ITP), sometimes associated with a syndrome resembling transient ischemic attack (TIA), suggesting a thrombogenic potential for PMP. To determine if this association applies to TIA and other cerebrovascular accidents (CVA) without ITP, we studied PMP profiles in 71 patients with ischemic CVA: 28 with small vessel CVA (SCVA), either lacunar infarcts or TIA; 24 with large vessel CVA (LCVA); 19 with multiinfarct dementia (MID); 12 with Alzheimer's dementia (AD); and 31 healthy controls. The mean PMP values were: MID = 3.71 +/- 0.51; SCVA = 3.48 +/- 0.63; LCVA = 1.97 +/- 0.28; AD = 1.19 +/- 0.27; controls = 0.88 +/- 0.09, (all units x 10(7)/mL). PMP values in all groups except AD were significantly above normal (p < 0.01). However, the elevation in SCVA was more marked than in LCVA (p < 0.01). Administration of the calcium channel blocker, nifedipine, to 11 TIA patients reduced PMP significantly.