Age, cholesterol, diabetes, family history...?

Edit: just saw that she is in her 30s and I'm assuming the labs show she's not anemic and white blood cells do not show cancer, calcium is in normal range. Probably should also have a chest x-ray. Based on the description, it's more likely anxiety.

That being said, I wouldn't bet my wife's life on it. I would still go through the necessary testing on the heart, but while that's getting tested, you could consider treating anxiety at the same time.