Heart attacks can be very mild, to debilitating. If the DR says not sufficient to install stents, then At sometime most likely you may feel a little chest pain, tightness. At the first sign of anything take one of the pills and stick it under your tongue. Which is probably what the DR suggested in perhaps a different way. After years of chest pains, a quad bypass in ‘98, two stents (one no longer working), I carry a bottle in my pocket or on a keychain all the time. They work well and quickly to quell the pain.
If one doesn't do it, my DR says try up-to three and then call 911.