Platelet aggregates in lung capillaries in severely decompensated pulmonary hypertension.

The mechanism of thrombocytopenia during acute pulmonary hypertension (PH) decompensation may be partly due to platelet aggregation in the lung. Platelet aggregates in explanted lung from 16 lung transplant patients during acute PH decompensation with and without thrombocytopenia were identified by immunohistochemistry. Scanning electron microscopy (SEM) was performed. 7 explant lung controls without PH and thrombocytopenia were also examined. Compared with controls, the median number of platelet aggregates was higher in patients with acute PH decompensation with thrombocytopenia (19.4 [IQR 3.4-38.3] vs 147.5 [IQR 26.5-203.2]). SEM showed capillaries filled with platelet aggregates. Our study suggests that platelets may aggregate in the lungs during acute PH decompensation.