Role of Platelets in Recurrent Deep Vein Thrombosis

To evaluate the role that platelets play in the pathogenesis of recurrent deep vein thrombosis (DVT), a platelet count ratio method was used for the detection of platelet aggregates and an aggregometric technique was used to measure spontaneous aggregation (SPA) in 27 patients with idiopathic recurrent DVT. Seventeen patients were found to have decreased platelet aggregate ratios (mean 0.63±SEM 0.02) which were significantly lower than those of normals (0.90 ±0.02, p < 0.01). Twelve of the 17 patients had SPA. The mean platelet survival half-time of 5 patients with increased platelet aggregates was 2.9 days±0.49, significantly decreased from that of normals (4.2 ±0.10, p < 0.05). Platelet survival values were normal in patients with normal platelet aggregate ratios. Five patients who failed to improve on oral anticoagulant therapy responded to aspirin and dipyridamole with normalization of platelet aggregates and disappearance of SPA. An additional patient responded to sulfinpyrazone. When the drug was discontinued, pulmonary embolus recurred. These findings suggest that recurrent DVT may involve heterogeneous groups of patients and platelets may play an important pathogenetic role in some of them. The approach to the problem with this panel of 3 tests appears useful in the selection of patients for treatment with antiplatelet agents.