Non-ST-elevation myocardial infarction

Part of the acute coronary syndrome spectrum. Usually caused by a partial or near-complete occlusion of a coronary artery resulting in compromised blood flow to myocardium with subsequent myocardial injury or infarction as demonstrated by elevation in troponin.

There are differences in typical presentation between the sexes. Male patients typically present with chest pressure/discomfort lasting at least several minutes, at times accompanied by sweating, dyspnea, nausea, and/or anxiety. Women present more commonly with middle/upper back pain or dyspnea and similar associated symptoms.

Symptoms are indistinguishable from those of unstable angina. However, non-ST-elevation myocardial infarction (MI) is differentiated from unstable angina by a rise of troponin.

ECG is the first-line investigation in all patients and should not be delayed for history, examination, or other tests.

Early risk stratification and treatment with anti-ischemic (beta-blockers, nitrates), anticoagulant (heparin), and dual antiplatelet agents (aspirin plus a P2Y12 receptor inhibitor) is needed. Higher-risk patients should be considered for an early invasive strategy (coronary angiography and revascularization in 12-24 hours).

Complications are progression or worsening of MI, heart failure, cardiogenic shock, arrhythmias, and death.

Non-ST-elevation myocardial infarction (NSTEMI) is an acute ischemic event causing myocyte necrosis. The initial ECG may show ischemic changes such as ST depressions, T-wave inversions, or transient ST elevations; however, it may also be normal or show nonspecific changes. If persistent ST elevation, evidence of posterior MI, or a new left bundle-branch block is present, then the patient should be evaluated as an ST-elevation myocardial infarction. NSTEMI, therefore, encompasses a broad spectrum of ischemic injury to the myocardium, which is detected by elevation of troponin.[1]Amsterdam EA, Wenger NK, Brindis RG, et al. 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014 Dec 23;64(24):e139-228. http://www.onlinejacc.org/content/64/24/e139 http://www.ncbi.nlm.nih.gov/pubmed/25260718?tool=bestpractice.com It can be distinguished from unstable angina pectoris by normal serial troponin.