Could be cheating. Maybe cheating or shopping for someone to cheat with caused the heart attack. Good luck to you
I would think it's more likely that the heart issues have caused him to re-evaluate his life. Some men believe that they can recapture their youth by being promiscuous and start looking for ways to do that. Some men buy sports cars or boats. Maybe you can try to take a step back and not take this personally (I know, I know) and try to see it as your hubby going through some emotional distress related to getting older. It might be easier for you to help him deal with this if you recognize that it's not you that's causing this.