Any Idea On A Travelling Swelling With A Pulsating Pain And On/off Chest Pain?

my husband went to the ER with a spot of swelling on his right arm near his arm pit with on and off chest pain, they checked him out and said EKG and the Xray was normal. Each day the swelling is traveling down his arm along the veins each day its getting worse. Today it is starting behind his left knee. He says it hurts with a pulsating pain. Like his arm is in a rubber band. Any ideas what this may be. We are set for a Doctor visit in a few days. But are unsure if we need to be pushing for an answer sooner.