Anyone have a type 2 MI, heart attack?

In 2020 I was diagnosed with PMR, ten months later I was off Pred., last month I had a type2 MI, heart attack. Is there anyone that has experienced this? I am vegetarian and have no coronary artery disease, all CT contrast and Angiogram showed no blockages. I even had a carotid artery evaluation and aorta, and there was not buildup of plaque. The test showed a heart 20 years younger than my chronological age, 76, I'm very active, gym, clubs, grandkids, this has been hard to understand. What do I do to prevent another heart attack?