Incidence and characteristics of spontaneous platelet macro-aggregation in acute ischemic stroke

Spontaneous platelet aggregation is a trigger for additional development of larger thrombi. Micro-aggregation is observed in 10% of diabetes approximately and blocked by P2Y12 inhibitors, whereas macro-aggregation is associated with overexpression of platelet α 2 -adrenoreceptors and is not blocked by conventional anti-platelet medicines. We examined the incidence of spontaneous platelet macro-aggregation (SPMA) in acute ischemic stroke and analyzed its clinical characteristics. Out of 665 consecutive acute ischemic strokes, SPMA was found in 10 patients (1.5%, one tenth of micro-aggregation) despite no detection in 588 control subjects. Types of ischemic stroke were 4 atherothrombotic, 4 cardioembolic, and 2 lacunar strokes. Stroke with SPMA exhibited higher (worse) values of modified Rankin Scales (mRS) at discharge (3.00 ± 0.53 vs 1.93 ± 0.07, p = 0.042 by Wilcoxon) compared with stroke without SPMA despite no difference at admission. The proportion of patients who were functionally independent (score 0–2 on the mRS) at discharge was lower in stroke with SPMA compared with stroke without SPMA (p < 0.05 by chi-square test; OR 3.60, 95% CI 1.08–12.03; RR 2.04, 95% CI 1.05–2.86). It was intriguing that severe (high magnitude) SPMA was observed in 4 atherothrombotic stroke. Although anti-platelet therapy underwent, the proportion of atherothrombotic patients who were functionally improved and independent at discharge was lower in the presence of SPMA compared with the absence of SPMA (p < 0.05 by chi-square test). The patients with SPMA were more likely to be older, having major disabilities, being less functionally improved during hospitalization, and being less functionally independent at discharge.