Happens all the time. Any doctor will tell you.
You mean it wasnt the KGB heart one punch?
Sad but true, my brother died from one 2 years ago and I had to go to the Emergency Room 6 months ago for a blood clot in my leg.
I got lucky, only 40% that get a clot get any notification something is wrong, like swelling and pain in the leg, the other 60% just up and die.