Acute coronary syndrome (main)

(Redirected from MI)

For risk stratification see ACS - Risk Stratification


  • Abbreviation: ACS
  • Refers to a spectrum of conditions compatible with acute myocardial ischemia and/or infarction that are usually due to an abrupt reduction in coronary blood flow.

Clinical ACS Categories

  1. ST-segment elevation myocardial infarction (30%)
  2. Non-ST-elevation myocardial infarction (25%)
  3. Unstable Angina (UA) (38%)
    • The new title, “Non-ST-Elevation Acute Coronary Syndromes,” emphasizes the continuum between UA and NSTEMI[1]
    • NSTEMI myocardium is damaged enough to increase biomarkers, UA is not.

MI Types by Causation[2]

Myocardial Infarction types by causation
  • Type 1: Spontaneous Myocardial Infarction
    • Atherosclerotic plaque rupture or intraluminal thrombus in one or more of the coronary arteries
  • Type 2: Myocardial Infarction Secondary to an Ischemic Imbalance
    • Condition other than CAD contributes to an imbalance between myocardial oxygen supply and/or demand (e.g. coronary spasm, embolism, low or high blood pressures, anemia, or arrhythmias)
  • Type 3: Cardiac Death Due to Myocardial Infarction
    • Sudden cardiac death with symptoms suggestive of myocardial ischaemia without elevated biomarkers
  • Type 4: Myocardial Infarction Associated With Revascularization Procedure
    • 4a: Related to PCI
    • 4b: Related to Stent Thrombosis
  • Type 5: Myocardial Infarction Related to CABG Procedure

Clinical Features

Risk of ACS

Clinical factors that increase likelihood of ACS/AMI:[3][4]

Clinical factors that decrease likelihood of ACS/AMI:[5]

  • Pleuritic chest pain
  • Positional chest pain
  • Sharp, stabbing chest pain
  • Chest pain reproducible with palpation

Gender differences in ACS

  • Women with ACS:
    • Less likely to be treated with guideline-directed medical therapies[6]
    • Less likely to undergo cardiac catheterization[6]
    • Less likely to receive timely reperfusion therapy[6]
    • More likely to report fatigue, dyspnea, indigestion, nausea or vomiting, palpitations, or weakness,[6] although some studies have found fewer differences in presentation[7]
  • More likely to delay presentation[6]
  • Men with ACS:
    • More likely to report central chest pain

Factors associated with delayed presentation[6]

  • Female sex
  • Older age
  • Black or Hispanic race
  • Low educational achievement
  • Low socioeconomic status

Differential Diagnosis

Chest pain




Elevated Troponin

True Positive

False (Non-CAD) Positives




ACS Anatomical Correlation Chart

Ischemic Changes Location Coronary Artery

Q waves in V1-V3 over time

Septal Septal branch
STE V2-V4 Anterior LAD
STE I, aVL, V5, V6

STD inf leads

Lateral Circumflex
STE I, aVL, V2-6 Anterolateral LAD + circumflex = Left main or 2 critical lesions

STD in aVL (most common lead to see reciprocal change)

Inferior RCA

STE V1 (only lead looking at RV)
STE III > II (III more R facing)
STE V1 > V2, STE V1 + STD V2

Right ventricle RCA

STD in V1, V2, V3;
R>S in V1
Tall R waves in V1-V3 (Q waves on back of heart) w/ upright TWs

Posterior aka Inferolateral RCA (90%), LCA (10%)
STE avR>V1

Doesn't apply in SVT

Anterolateral Left Main


Intensity of treatment should be based on ACS likelihood


  • Admit
    • Ischemic ECG changes
    • Pacemakers
    • LBBB
    • Positive troponins
    • Abnormal vital signs
  • ACC/AHA rec need for provocative testing withing 72 hrs, consider admitting
  • For low risk (HEART) pts, may be better off discharge home with follow up[8]
    • Risk of MACE after neg ED work up 1/2422 vs Risk of preventable adverse event in hospital is 1/164


External Links

See Also


  1. AHA ACA - NSTEMI ACS Guidelines 2014 View Online
  2. Third Universal Definition of Myocardial Infarction
  3. Body R, Carley S, Wibberley C, et al. The value of symptoms and signs in the emergent diagnosis of acute coronary syndromes. Resuscitation. 2010;81(3):281–286. PMID: 20036454
  4. Panju AA, Hemmelgarn BR, Guyatt GH, et al. The rational clinical examination. Is this patient having a myocardial infarction? JAMA. 1998;280(14):1256–1263. PMID: 9786377
  5. Swap CJ, Nagurney JT. Value and limitations of chest pain history in the evaluation of patients with suspected acute coronary syndromes. JAMA. 2005;294(20):2623–2629. PMID: 16304077
  6. 6.0 6.1 6.2 6.3 6.4 6.5 Mehta LS, et al. Acute myocardial infarction in women: A scientific statement from the American Heart Association. Circulation. 2016; 133:916-947.
  7. Gimenez MR, et al. Sex-specific chest pain characteristics in the early diagnosis of acute myocardial infarction. JAMA Intern Med. 2014; 174(2):241-249.
  8. Weinstock MB, Weingart S, Orth F, VanFossen D, Kaide C, Anderson J, Newman DH. Risk for Clinically Relevant Adverse Cardiac Events in Patients With Chest Pain at Hospital Admission. JAMA Intern Med. 2015 Jul;175(7):1207-12.