Acute DVT
Deep vein thrombosis (DVT or venous thrombosis) occurs when a blood clot forms in a vein deep inside your body. DVT mainly affects the large veins in the lower leg and thigh, but can occur in other deep veins, such as in the arms and pelvis. DVT can occur suddenly (acute), leading to an urgent or emergency situation.
Chronic DVT
A clot that is over one to two months old is called “chronic.” The clot becomes harder and scars the vein. As a result of this process, the vein becomes much smaller and does not allow blood to flow through effectively.