Cluster 552: venous thrombosis thromboembolism arterial deep history embolism months pulmonary patients 
Cluster 813: thrombosis deep vein embolism pulmonary dvt history pe months venous 
Cluster 1873: embolus deep thrombosis pulmonary vein history months venous patients enrollment 
Cluster 1899: dvt deep thrombosis embolism venous accident cerebrovascular attack transient pulmonary