Not that uncommon.
Owner in his heart attack and operating table examination was put under the fluoroscope (is that what it's called?) and they injected "dye" into each vein and followed the path of the blood through the heart in each case. Owner says that 4 of his feeds were "100 percent clear" - the 5th was 100 percent blocked. Otherwise known as the "widowmaker."
A widowmaker heart attack happens when you have a blockage in your heart’s largest artery. Emergency treatment is important to improve your survival odds.
my.clevelandclinic.org
Normal hearts have 4 major feeds. A small percentage of the population have more. In Owner's case he's one of the 11 percent of the population who have 5 - it's probably what saved him.
One imagines that in examination, many artery's are found "partially blocked." In these cases they don't mess around - but go right to a bypass. Thus you may be headed under the knife for one or two - but end up with more "because it's convenient and a sure fix."
They addressed Owner's heart attack with "Angioplasty" - which is convenient because it can be done entirely from outside the body using a catheter. "Stents" had just been developed but were not common then. Angioplasty has the advantage of ease of execution, but the downside in that it may "reclose." Stents prevent this.
For two years after Owner's heart attack, he was required to come back for "evaluation" of the performance of his angioplasty - a "just in case of closure."
Dobbin
