How is myocardial infarction (MI, heart attack) associated with acute coronary syndrome (ACS)?

Updated: May 07, 2019
  • Author: A Maziar Zafari, MD, PhD, FACC, FAHA; Chief Editor: Eric H Yang, MD  more...
  • Print
Answer

MI is considered part of a spectrum referred to as acute coronary syndrome (ACS). The ACS continuum representing ongoing myocardial ischemia or injury consists of unstable angina, non–ST-segment elevation MI (NSTEMI)—collectively referred to as non–ST-segment acute coronary syndrome (NSTE ACS)—and ST-segment elevation MI (STEMI). Patients with ischemic discomfort may or may not have ST-segment or T-wave changes denoted on the electrocardiogram (ECG). ST elevations seen on the ECG reflect active and ongoing transmural myocardial injury. Without immediate reperfusion therapy, most patients with STEMI develop Q waves, reflecting a dead zone of myocardium that has undergone irreversible damage and death.

Those without ST elevations are diagnosed either with unstable angina or NSTEMI―differentiated by the presence of cardiac enzymes. Both these conditions may or may not have changes on the surface ECG, including ST-segment depressions or T-wave morphological changes.


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!