Welcome to HCM,
After going through your history you have coronary artery
disease and treated with 8 stents, I am sure you must be taking required medicines for it.
When you have chest pain
and there are no changes in EKG and every other parameter is normal this can happen.
If you have chest pain there is strong possibility of angina
so it must be investigated by not only resting EKG but by Holter Monitoring and tests to induce ischemia
like Stress test
may be Thallium.
If there are lesion which have been taken care by stents then microvascular Ischemia is possible which you have to discuss with your Cardiologist.
Otherwise optimal medical antianginal therapy should continue and you should take rest.
If sub optimal result are there with stents then possibility of CABG may be discussed with Cardiothoracic surgeon.
Angina is clinical diagnosis it may come in test or it may not come.
Please take care