Author:
Adam S.Kaye
Shamai A.Grossman
Description
- Cardiac reperfusion therapy is required on patients that present with ST-segment elevation myocardial infarction (STEMI)
- Early percutaneous coronary intervention (PCI), but not fibrinolytics may be considered in those with unstable angina (UA)/non-ST-segment elevation MI (NSTEMI)
- Fibrinolytic therapy:
- Reduces morbidity and mortality in STEMI in cases where PCI is not available in <120 min
- The earlier fibrinolytics are started, the more myocardium is salvaged
- Goal of fibrinolytic therapy is a door-to-needle time of 30 min if PCI is not planned or delayed >120 min
- PCI:
- Balloon inflation, stent placement, and thrombus removal are possible options in the cath lab and result in overstretching of vessel wall and partial disruption of intima, media, and adventitia, resulting in enlargement of lumen and outer diameter of diseased vessel and restoration of epicardial coronary arterial flow
- Goal of primary PCI is a door-to-balloon time of 90 min from first medical contact for STEMI or <120 min if at a non-PCI center
- Stent placement decreases early and late loss in luminal diameter seen with percutaneous transluminal coronary angioplasty (PTCA)
- PCI provides greater coronary patency and thrombolysis in MI flow than do fibrinolytics and decreased mortality and morbidity
- Lower risk of bleeding than with fibrinolytics
- PCI can be both diagnostic as well as therapeutic
- PCI should be strongly considered within first 48 hr after NSTEMI in discussion with a cardiologist
- Glycoprotein IIb/IIIa inhibitors:
- Antiplatelet agents that bind to platelet receptor glycoprotein IIb/IIIa and inhibit platelet aggregation
- Reduce mortality and reinfarction rate in patients in whom PCI is planned; reasonable to administer at time of primary PCI
- Not indicated for patients with STEMI, unless also undergoing PCI
- Unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH):
- Adjuncts in treatment with aspirin, clopidogrel, fibrinolytics, glycoprotein IIb/IIIa inhibitors, and PCI
- Anticoagulant therapy with either UFH or LMWH is indicated in patients with either STEMI (with PCI or fibrinolytics) or UA/NSTEMI
- Clopidogrel or prasugrel should be added to stand ard therapy regardless of whether PCI or reperfusion therapy is planned
- Statin therapy reduces clinical events in patients with stable coronary artery disease. This may also extend to patients experiencing an acute ischemic coronary event
- Post arrest patients may have therapeutic hypothermia initiated in the ED prior to PCI or during PCI
Etiology
- STEMI is caused by occlusion of an epicardial coronary artery, usually as a result of a thrombotic event
- UA/NSTEMI is caused by a partial occlusion of coronary artery, also due to thrombus
Signs and Symptoms
- Chest pain, heaviness, or pressure
- Shortness of breath
- Arm, neck, or back pain
- Weakness or fatigue
- Nausea, vomiting
- Diaphoresis
- Palpitations
- Dizziness or syncope
- ECG changes
Essential Workup
- History is critical in assessing window for use of both fibrinolytics and PCI
- ECG:
- Will be normal ∼50% of time
- Must be compared with prior tracings if available and may evolve in short period of time, consider repeat ECGs
- ST-elevation in the absence of left ventricular hypertrophy or left bundle branch block (LBBB) with new ST-elevation at the J-point in at least 2 contiguous leads of ≥2 mm in men or ≥1.5 mm in women in leads V2-V3 and /or of ≥1 mm (0.1 mV) in other contiguous chest leads or the limb leads
- New or presumably new LBBB has been considered a STEMI equivalent in the past. However, most cases of LBBB at time of presentation; however, are “not known to be old” because prior ECG is not available for comparison
- New or presumably new LBBB at presentation occurs infrequently, may interfere with ST-elevation analysis, and should not be considered diagnostic of acute myocardial infarction (MI) isolation without symptoms of ACS; use of Sgarbossa criteria is recommended for definitive diagnosis
- Baseline ECG abnormalities other than LBBB (e.g., paced rhythm, LV hypertrophy, Brugada syndrome) may obscure interpretation
- New ST-segment changes or T-wave inversions are suspicious for UA or non-Q-wave infarct
- 1-mm depression of the ST segment below the baseline, 80 ms from the J-point, is characteristic of UA or non-Q-wave infarct
- CXR May be helpful in assessing for alternate diagnoses including aortic dissection or pneumothorax, but isn't mand atory
- Heme stool test: Can be helpful if considering anticoagulation
Diagnostic Tests & Interpretation
Lab
- Cardiac enzymes, troponin preferred
- Baseline creatinine, hematocrit, and coagulation profile are all appropriate in initial workup
Differential Diagnosis
- Aortic dissection
- Biliary colic
- Coronary aneurysm
- Costochondritis
- Esophageal pathology
- Herpes zoster
- Hiatal hernia
- Hyperkalemia
- Mitral valve prolapse
- Peptic ulcer disease
- Psychogenic symptoms
- Pericarditis
- Pneumonia
- Pulmonary embolus
- Ventricular aneurysm
Prehospital/Initial Stabilization
- IV access
- Cardiac monitoring
- Aspirin 162 or 325 nonenteric coated
- Oxygen - if hypoxic
- Sublingual nitroglycerin for symptom relief, unless hypotensive, evidence of RV infarct, or recent use of PDE-5 inhibitors such as sildenafil or tadalafil
- Local EMS system and hospital system should preferentially transport STEMIs to PCI-capable hospital
- Controversies:
- Whether to allow EMS activation of cardiac catheterization labs and administration of fibrinolytics
ALERT |
- All chest pain should be treated and transported as a possible life-threatening emergency
- Therapy with fibrinolytics and glycoprotein IIb/IIIa inhibitors in the field is not currently stand ard of care
|
ED Treatment/Procedures
- Aspirin
- Clopidogrel
- Fibrinolytics for STEMI:
- Are considered inferior to PCI unless PCI is not available within 120 min
- PCI is preferred as it is both diagnostic and offers superior therapeutic options for STEMI and UA/NSTEMI
- PCI and fibrinolytics therapy must be used with either UFH or an LMWH, such as enoxaparin or bivalirudin
- LMWH:
- Kinetics more predictable
- Requires no monitoring
- Less potential for platelet activation
- Lower bleeding rate
- Is at least as effective as UFH in treatment of acute coronary syndromes
- Glycoprotein IIb/IIIa inhibitors
- Direct thrombin inhibitors - bivalirudin if history of heparin-induced thrombocytopenia
Medication
Antiplatelet agents:
- Aspirin: 162-325 mg PO nonenteric coated
- Clopidogrel (Plavix): 300-600 mg PO load, 75 mg PO per day
- Prasugrel: 60 mg PO load, 10 mg PO per day
- Not to be used in patients with history of TIA or stroke
- Ticagrelor: 180 mg PO load, 90 mg PO b.i.d
Glycoprotein IIb/IIIa inhibitors:
- Abciximab (ReoPro): For use before PCI only; 0.25 mg/kg IV bolus; 0.125 mcg/kg/min to a max of 10 mcg/min for 12 hr
- Eptifibatide (Integrilin): 180 mcg/kg IV over 1-2 min, followed by continuous IV infusion of 2 mcg/kg/min (max 15 mg/hr) up to 72 hr
- Tirofiban (Aggrastat): 0.4 mcg/kg/min for 30 min, then 0.1 mcg/kg/min for 48-108 hr
Anti-Xa agents:
- Heparin: 60 U/kg IV bolus (max 4,000 U), then 12 U/kg/hr (max 1,000 U/hr) must be adjusted to target aPTT
- Enoxaparin (Lovenox): (Bolus with 30 mg IV if STEMI patient age <75) 1 mg/kg SC q12h - see additional dosing guidelines for elderly patients and renal impairment
- Bivalirudin: 0.1 mg/kg bolus, followed by 0.25 mg/kg/hr for UA/NSTEMI (no PCI) and 0.75 mg/kg bolus, followed by 1.75 mg/kg/hr in STEMI or UA/NSTEMI undergoing early PCI
β-blockers:
- Metoprolol: IV 5 mg q5min up to 3 doses IV metoprolol is only indicated in STEMI patients who are hypertensive or have ongoing ischemia without contraindication. Oral metoprolol should be started within 24 hr of STEMI unless there are signs of cardiogenic shock 25-50 mg PO q6-12 starting dose as tolerated (note: β-blockers contraindicated in cocaine chest pain)
Fibrinolytics:
- Streptokinase: 1.5 million units over 60 min; patients should also receive methylprednisolone 250 mg IV
- Alteplase: 15 mg IV bolus, then 0.75 mg/kg (max 50 mg) over 30 min, then 0.5 mg/kg (max 35 mg) over 60 min; patients should also receive heparin
- Tenecteplase: Weight-based dosing with max single dose of 30-50 mg given over 5 s; IV bolus over 5 s
- Contraindications:
- Active internal bleeding
- History of cerebrovascular accident in last 6 mo
- History of a hemorrhagic cerebrovascular accident
- Recent (within 2 mo) intracranial or intraspinal surgery or trauma
- Intracranial neoplasm, arteriovenous malformation, or aneurysm
- Trauma or surgery within last 2 wk that may result in closed-space bleed
- Relative contraindications:
- Known bleeding diathesis
- Severe, uncontrolled hypertension
- Pregnancy
- Head trauma within last month
Disposition
Admission Criteria
All patients being considered for reperfusion therapy should be admitted to a cath lab or transferred to a PCI center or admitted to tele bed or an ICU setting
Discharge Criteria
No patient being considered for reperfusion therapy should be discharged home from ED
- American College of Emergency Physicians; Society for Cardiovascular Angiography and Interventions, O'GaraPT, et al. 2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines . J Am Coll Cardiol. 2013;61:e78-e140.
- AmsterdamEZ, WengerNK, BrindisRG, et al. 2014 AHA/ACC Guideline for the Management of Patients With Non-ST-Elevation Acute Coronary Syndromes . J Am Coll Cardiol. 2014;64:e139-e228.
- IbanezB, JamesS, AgewallS, et al. 2017 ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation: The Task Force for the management of acute myocardial infarction in patients presenting with ST-segment elevation of the European Society of Cardiology . Eur Heart J. 2018;39:119-177.
See Also (Topic, Algorithm, Electronic Media Element)
The authors gratefully acknowledge Joshua J. Solano for his contribution to the previous edition of this chapter.
ICD9
410.90 Acute myocardial infarction, unspecified site, episode of care unspecified
ICD10
I21.3 ST elevation (STEMI) myocardial infarction of unspecified site
SNOMED