Final answer:
When ischemia is prolonged and is not immediately reversible, it is classified as Acute coronary syndrome. Acute coronary syndrome encompasses Unstable angina (UA), Non-ST-segment-elevation myocardial infarction (NSTEMI), and ST-segment-elevation MI (STEMI).
Step-by-step explanation:
When ischemia is prolonged and is not immediately reversible, it is classified as Acute coronary syndrome. Acute coronary syndrome encompasses Unstable angina (UA), Non-ST-segment-elevation myocardial infarction (NSTEMI), and ST-segment-elevation MI (STEMI). Unstable angina is angina in which pain occurs during rest, lasts more than 15 minutes, and is of new onset. It requires urgent medical attention. NSTEMI and STEMI are both types of myocardial infarction, commonly known as a heart attack. NSTEMI is characterized by non-ST-elevation on an electrocardiogram (ECG), while STEMI is characterized by ST-elevation on an ECG.