Assuming you get to a resus bed in hospital, have faith in your medics during your stay. "What? you'd been told you just need to have faith in God" The word "God" could blur. You just need faith [period]. Maybe God is goodness; that people studied medicine?
Surviving a heart attack and any associated cardiac arrest, might go beyond "resus" in A&E. You may have been self-reliant. Now you might have needed others, more than anytime in your life. You're probably numerical mature in age. You and your peers could have gotten through life without any "major wake-up calls", until this point. (I was 55). It may have been a brutally severe experience, and too much for anyone.
Some people though, are so used to challenges and setbacks, that fates like this are in a figurative "day's work", and furthermore, clichéd phrases like, "pick oneself up; dust oneself down, and carry on", may suit, if physically and mentally possible. The latter part, to carry on, is the only deal worthy of consideration. You can dwell and feel sorry for yourself, but for how long?
Introspection is one of the most powerful human processes, and it might begin by a gift in disguise; perhaps even masquerading as a heart attack. Like Rumi said, "the cure for pain, is in the pain" ?
Something made a 99-year-old gentleman from Brentwood (reported in the BBC website page linked below), get baptised and confirmed in the Church of England, at such a remarkable point in life.
BTW: I'm not trying to proselytise for the CofE, or any religious organisations in the broader sense. I'm just trying to point out, that there are no time limits to make personal changes !