Having had open heart surgery a decade ago to repair my valve and fix an ascending aortic aneurysm, I'm familiar with Armstrong and Paxton. Paxton had a similar operation to mine:https://doctordaliah.wordpress.com/...eurysm-repair-prior-to-his-fatal-stroke/
And a stroke got him. What I don't know is if it happened when they were warming him up after surgery, or after he was warm and threw plaque or a clot. When you have this kind of surgery, your brain is either completely disconnected from blood flow, or a machine processes the blood for a time while the surgeon repairs your ascending aorta. Your body is also chilled to the point that the metabolism of the brain nearly stops, thus protecting it from oxygen deprivation. A big risk from this surgery is if your body is warmed too quickly afterwards, bubbles can form in the blood which can cause a stroke. Needless to say I was very anxious going in, and asked my surgeon on the table to warm me very slowly. The risks are there, and I was blessed with waking up okay, though I do recall the world looking like vertical hold had broken on a television set for a day. I feel bad about Bill, he was an awesome actor.
Armstrong died from bleeding that occured after they removed his heart electrodes. When you have these surgeries that require cracking the chest, common practice was to implant drainage tubes for the pericardium and chest cavity, and electrodes to maintain a steady heart rhythm. The drainage tubes are pretty nasty because all sorts of fluid and blood comes out, and when they yank them out is very unpleasant. I remember blood oozing from the two holes for a day after they were removed, and formed three inch long dangling scabs. As for the electrodes removed, that was one of the wildest sensations I've ever felt. I remember when the nurse got up on the bed upon her knees, bent over my chest and grabbed the electrode harness with a tight fist and yanked hard. My body felt as if a web of sparks crawled across and through my chest like a star exploded inside of me. Afterwards, I felt fine.
Long story short, heart surgery sucks. I'm glad I had mine though. Word of advice to anyone that may face such a surgery: interview multiple surgeons and find one that specializes in exactly what you are having done. Mine did 140 such surgeries a year, and was one of the best in the world. Fortunately I had insurance that allowed me to choose him.