ECG without evident changes for a heart attack, doesn't exclude a heart attack.
Actually, the chest pain can be a symptom of subtype of heart attack, known as heart attack without characteristic ECG changes.
Another possibility is that you might experienced a episode of unstable angina (chest pain occurs suddenly, often at rest or with minimal exertion), and this is a warning sign that a heart attack may happen soon, so it requires treatment right away.
Unstable angina occurs without elevated cardiac enzymes or ST-segment elevation on EKG. If there are elevated cardiac enzymes but no ST-segment elevation, it is called non-ST elevation myocardial infarction.
Troponin test is a late marker and is usually performed 12 hours aftre onset of chest pain.
When its levels are increased, coronary angiography is typically performed on an urgent basis, as this is highly predictive of a heart attack in the near-future.
