I thought I would add my recent experience. On the off chance I went to the doctor with an irritating cough and happened to mention that I had a large bruise on my finger ( although no pain) and was having periods when it was numb and cold. She referred me to a hand surgeon the next morning who gave me blood thinners there and then in his office. He pointed out that it was not a bruise but a blood clot that had cut off the blood supply. An angiogram scan showed no blood flow to the righ side when my arm was raised, and within 10 days I was in for surgery. On the positive side, a year on and the removal of my rib and the scalenectomy has solved the problem, however I have 5 years before surgery needed on the other side. I am now aware of what to look for and the surgery is pretty traumatic, however within 3 months I was back on my feet with light gym work. A year on I have numb skin around my collarbone and sensitivity but a good outcome.
Hope this helps