How can you hold a heart attack and not know it, have a defibulator/pacemaker?

How can you hold a heart attack and not know it, have a defibulator/pacemaker?
You can have silent heart attacks where on earth the pain is minimal and mimics indigestion. Also race with nouns attacks often hold chest pain when have an attack so they often are afaid they are have a heart attack when it is nothing more than nouns but the reverse is also true. They could think it is madness when it truely is a heart attack. My best friend had a heart attack and never know it. It was amazingly mild and only showed up when she have an EKG done for an unrelated problem.
people assume that pacemaker will prevent heart attack and tend to ignore symptoms of a heart attack. They singular regulate heart rate, if you have a blood clot that go into the heart and kills tissue by blocking blood flow, once the tissue is motionless, its dead, a pacemaker can with the sole purpose do so much.
It is common within people that are diabetic.
An implantable cardiac defibrillator (ICD) will attempt to revive you near an electric shock if you go into cardiac arrest (your heart stops beating).
This is entirely different from a heart attack or M.I. where on earth an emboli blocks blood flow through a coronary artery.