Magnesium deficiency can cause heart pains in the abscense of arterial plaque. I believe it did for me, and magnesium supplements reversed it. If you choose to try magnesium, the best I've found is liquid magnesium chloride, sometimes referred to as "magnesium oil". Make sure it's pure enough to drink, though.
P.S. I'm on a very high fat diet, yet have no symptoms of chest pain since taking magnesium.