Episode 34 – Emergency Department Management of Non–ST-Segment Elevation Myocardial Infarction

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Part 1: Definitions

• Myocardial Infarction: elevated cardiac biomarkers (aka troponin) with clinical evidence of acute myocardial ischemia (aka signs and symptoms, ECG changes, abnormal imaging, or coronary thrombosis at cath or autopsy).
• Myocardial injury, unfortunately also can be abbreviated as MI, but not in our discussion. This term refers solely to cases where biomarker elevation is present without any other clinical evidence for ischemia.

STEMI definition from the European Society of cardiology:

1. ST elevation >1mm in two or more contiguous leads other than V2-V3
2. ST elevation in V2-V3
   1. > 2.5mm in med < 40 yrs old
   2. >2 mm in men > 40 yrs old
   3. >1.5mm in woman, regardless of age.

MACE= Major Adverse Cardiovascular Event: including re-infarction, stroke, dysrhythmia, heart failure, cardiogenic shock, and death.

Part 2 : Why do we care?

• In-hospital mortality rates are about the same for STEMI and NSTEMI, about 10%.
• 1-year fatality rate in NSTEMI is more than double that of STEMI, at about 25%

Part 3: Pathophysiology

• Type 1 MI (Infarction) is caused by atherosclerotic plaque rupture.
• Type 2 MI is the “mismatch” due to an imbalance in myocardial oxygen supply and demand. This can be the result of hypotension, tachycardia, sepsis, PE, etc.

Part 4: Pre-hospital care

• Prehospital ECGs decrease time to intervention. (PCI) in STEMI
• Early administration of aspirin decreases mortality and complications of MI (all types). (19), and is safe in the pre-hospital setting (20) – only 45% of get it during EMS transport, so room for improvement here (21)

Part 5: ED evaluation: Some of the interesting highlights

History

• Diaphoresis
• Vomiting
• Radiation of pain to both arms or shoulders
• Radiation of pain to right shoulder
• Although teaching has been that women have atypical presentations, a 2016 study did not support it. However, it did find that elderly patients and those with diabetes may present atypically. (dyspnea, fatigue, nausea, or epigastric pain)

Past Medical History

• Family and personal history of CAD
• Other medical diagnoses
• Tobacco use
• Illicit substance abuse
• Age (CAD prevalence in age<40 is 1%, age >80 is 25%)
• ** HIV – find citing
  • 8. Grunfeld C, Delaney JA, Wanke C, et al. Preclinical atherosclerosis due to HIV infection: carotid intima-medial thickness measurements from the FRAM study. AIDS (London, England). 2009;23(14):1841–9. [PMC free article] [PubMed] [Google Scholar]
  • 9. Holloway CJ, Ntusi N, Suttie J, et al. Comprehensive cardiac magnetic resonance imaging and spectroscopy reveal a high burden of myocardial disease in HIV patients. Circulation. 2013;128(8):814–22. [PubMed] [Google Scholar]
• ** Cancer with hx of radiation to the chest

Exam

• Neurological neurologic deficit may point to aortic dissection
• Friction rub may be heard
• New murmur associated with papillary muscle rupture.

Diagnostics

• Telemetry
• ECG. Patterns to know…
• Troponin… you should get it

Scoring systems

• Heart Score
• Grace
• TIMI

Imaging in the ED

• CXR
• CT angiography, CT PE, CCTA
• Echocardiography – POC or formal

Part 6: Medications

• Oxygen (if sat <90%)
• Morphine (no)
• Nitrates
• Aspirin
• Antiplatelet agents
  • PSY12 inhibitors
  • IIb/IIIa inhibitors
• Heparins
• Beta Blockers
• Statins

Part 7: Revascularization

Immediate/urgent revascularization is recommended for all patients with NSTEMI who show signs of clinical instability, including refractory angina, sustained ventricular dysrhythmias, new or worsening heart failure, or shock (AHA class Ia recommendation; ESC class Ic recommendation). Otherwise, there is no clear benefit to immediate revascularization on all NSTEMI patients.

Part 8: The Specials…

• Women
• Black Patients
• Young Patients
• Diabetics
• Cocaine Users