Rosen & Barkin's 5-Minute Emergency Medicine Consult (32 page)

• Imbalance in myocardial blood supply and oxygen requirement
  
• Acute coronary syndrome (ACS) encompasses a spectrum of disease processes:
  
  • Unstable angina pectoris
    
  • Acute myocardial infarction (AMI)
    
  • ST elevation myocardial infarction (STEMI)
    
  • Non-STEMI
    

• Atherosclerotic narrowing of coronary vessels
  
• Vasospasm (Prinzmetal or variant angina)
  
• Microvascular angina or abnormal relaxation of vessels with diffuse vascular disease
  
• Plaque disruption
  
• Thrombosis
  
• Arteritis:
  
  • Lupus
    
  • Takayasu disease
    
  • Kawasaki disease
    
  • Rheumatoid arthritis
    
• Prolonged hypotension
  
• Anemia/stress ischemia:
  
  • Hemoglobin <8 g/dL
    
• Carbon monoxide/elevations in carboxyhemoglobin
  
• Coronary artery gas embolus
  
• Thyroid storm
  
• Structural abnormalities of coronary arteries:
  
  • Radiation fibrosis
    
  • Aneurysms
    
  • Ectasia
    
• Cocaine- or amphetamine-induced vasospasm
  
• Cardiac risk factors include:
  
  • Hypercholesterolemia
    
  • DM
    
  • HTN
    
  • Smoking
    
  • Family history in a 1st-degree relative <55 yr old
    
  • Men, age >55 yr
    
  • Postmenopausal women
    

DIAGNOSIS

• Chest pain:
  
  • Most common presentation of MI
    
  • Substernal pressure
    
  • Heaviness
    
  • Squeezing
    
  • Burning sensation
    
  • Tightness
    
• Anginal equivalents (MI without chest pain):
  
  • Abdominal pain
    
  • Syncope
    
  • Diaphoresis
    
  • Nausea or vomiting
    
  • Weakness
    
• May localize or radiate to arms, shoulders, back, neck, or jaw
  
• Associated symptoms:
  
  • Dyspnea
    
  • Syncope
    
  • Fatigue
    
  • Diaphoresis
    
  • Nausea
    
  • Vomiting
    
• Symptoms are usually reproduced by exertion, eating, exposure to cold, or emotional stress.
  
• Symptoms commonly last 30 min or more.
  
• Symptoms may occur with rest or exertion.
  
• Often preceded by crescendo angina
  
• May be improved/relieved with rest or nitroglycerin
  
• Symptoms generally unchanged with position or inspiration
  
• Positive Levine sign or clenched fist over chest is suggestive of angina.
  
• BP is usually elevated during symptoms.
  

• Physical exam is usually unrevealing.
  
• Occasional physical findings include:
  
  • S3 or S4 due to left ventricular systolic or diastolic symptoms
    
  • Mitral regurgitation due to papillary muscle dysfunction
    
  • Diminished peripheral pulses
    
  • Physical findings of decompensated CHF
    

History is critical in differentiating MI from noncardiac etiologies.

• Electrolytes
  
• Calcium, magnesium
  
• Cardiac enzymes
  
• Digoxin level
  

• CXR:
  
  • May identify cardiomyopathy or CHF
    
  • Often abnormal in aortic dissection
    

• ECG:
  
  • Differentiate from nonischemic causes of ST elevation
    
    • Pericarditis
      
    • Benign early repolarization
      
    • Left ventricular hypertrophy with strain
      
    • Prior MI with left ventricular aneurysm
      
    • Hyperkalemia
      
• ECG criteria for STEMI
  
  • New ST elevation at J point in at least 2 contiguous leads of 2 mm (0.2 mV) in men or 1.5 mm (0.15 mV) in women in leads V2–V3 and/or of 1 mm (0.1 mV) in other contiguous chest leads or the limb leads
    
  • ST depression in leads V1–V2 may indicate posterior injury
    
  • New or presumably new LBBB has been considered an STEMI equivalent. Most cases of LBBB at time of presentation, are not old but prior ECG is unavailable
    
  • Sgarbossa criteria for MI in LBBB are diagnostic
    
    • Concordant ST elevation >1 mm in leads with a positive QRS complex
      
    • Concordant ST depression >1 mm V1–V3
      
    • Excessively discordant ST elevation > 5 mm in leads with a negative QRS complex
      
• Echo:
  
  • May identify regional wall motion abnormalities or valvular dysfunction
    

• Aortic dissection
  
• Anxiety
  
• Biliary colic
  
• Costochondritis
  
• Esophageal spasm
  
• Esophageal reflux
  
• Herpes zoster
  
• Hiatal hernia
  
• Mitral valve prolapse
  
• Peptic ulcer disease
  
• Psychogenic symptoms
  
• Panic disorder
  
• Pericarditis
  
• Pneumonia
  
• Pulmonary embolus
  

TREATMENT

• IV access
  
• Aspirin
  
• Oxygen
  
• Cardiac monitoring
  
• Sublingual nitroglycerin for symptom relief
  
• 12-lead ECG, if possible, with transmission or results relayed to receiving hospital
  

• IV access
  
• Oxygen
  
• Cardiac monitoring
  
• Oxygen saturation
  
• Continuous BP monitoring and pulse oximetry
  

• STEMI requires reperfusion therapy as soon as possible:
  
  • Percutaneous coronary intervention (PCI) is preferred diagnostic and therapeutic modality if available.
    
• Goal is primary PCI within 90 min of 1st medical contact.
  
  • Thrombolytics should be given if PCI is not available within 120 min of 1st medical contact (see “Reperfusion Therapy, Cardiac”).
    
• Aspirin should be administered 1st to all patients with suspected MI unless known allergy.
  
• Glycoprotein IIb/IIIa inhibitors (e.g., Abciximab) may be started at time of PCI
  
• Prasugrel or Clopidogrel should be started at the time of PCI
  
• Prasugrel should not be given to patients with history of prior stroke or TIA
  
• Clopidogrel is the recommended ADP receptor inhibitor for patients given fibrinolytics
  
  • Dose is reduced (age <75 yr: 300 mg, >75 yr: 75 mg)
    
• If BP is >90–100 mm Hg systolic, administer sublingual nitroglycerin, nitropaste, or IV nitroglycerin assuming no ECG criteria or clinical evidence of right ventricular infarct:
  
  • Symptoms that persist after 3 sublingual nitroglycerin tablets are strongly suggestive of AMI or noncardiac etiology.
    
• β-blockers should be initiated within 1st 24 hr if not contraindicated (e.g., heart block, heart rate <60, signs of heart failure, hypotension, or obstructive pulmonary disease) are present
  
  • No benefit of administration prior to PCI or in ED
    
• Morphine may be given to relieve pain, anxiety, and increase oxygen carrying capacity.
  
• Heparin (UFH) or Bivalirudin should be used in patients undergoing primary PCI. Bivalirudin is indicated in patients at high risk for bleeding.
  
• In patients undergoing thrombolysis, Heparin (UFH), Enoxaparin, or Fondaparinux are appropriate.
  
• If patient is in cardiogenic shock, patient should be transported to a cardiac catheterization laboratory for angioplasty and intra-aortic balloon pump as soon as possible (see “Congestive Heart Failure”).
  
• Ventricular dysrhythmias:
  
  • See “Ventricular Tachycardia”
    
• Bradydysrhythmia associated with hypotension should be treated with atropine or external pacing.
  
• Conduction disturbances:
  
  • 1st-degree atrioventricular (AV) block and Mobitz I (Wenckebach) are often self-limited and do not require treatment.
    
  • Mobitz II, complete heart block, new right bundle branch block (RBBB) in anterior MI, RBBB plus left anterior branch block or left posterior fascicular block, left bundle branch block plus 1st-degree AV block may require a temporary transvenous pacemaker.
    
• Accelerated idioventricular rhythm (AIVR) may present after reperfusion, appearing as a ventricular rhythm with rate below 120 bpm
  
  • Only if sustained treat with electrical cardioversion or sodium bicarbonate
    
  • Lidocaine and other antidysrhythmics may cause asystole
    

• Aspirin: 162–325 mg PO
  
• ADP receptor inhibitors
  
  • Clopidogrel (Plavix): 600 mg PO
    
  • Prasugrel (Effient): 60 mg PO
    
  • Ticagrelor (Ticlid): 180 mg PO
    
• Bivalirudin: 0.75 mg/kg IV bolus, then 1.75 mg/kg/h infusion
  
• Enoxaparin (Lovenox): 1 mg/kg SC q12h
  
  • Fondaparinux: 2.5 mg IV
    
• Glycoprotein IIb/IIIa inhibitors:
  
  • Abciximab (ReoPro) for use prior to PCI only: 0.25 mg/kg IV bolus
    
  • Eptifibatide (Integrilin): 180 μg/kg IV over 1–2 min, then 2 μg/kg/min up to 72 hr
    
  • Tirofiban (Aggrastat): 0.4 μg/kg/min for 30 min, then 0.1 μg/kg/min for 48–108 hr
    
• Heparin: 60 units/kg IV bolus (max. 4,000 U), then 12 U/kg/h (max. 1,000 U/h)
  
• Metoprolol: 5 mg IV q5–15min followed by 25–50 mg PO starting dose as tolerated (note: β-blockers contraindicated in cocaine chest pain)
  
• Morphine: 2 mg IV, may titrate upward in 2 mg increments for relief of pain assuming no respiratory deterioration and SBP >90 mm Hg
  
• Nitroglycerin: 0.4 mg sublingual q5min for max. 3 doses
  
• Nitroglycerin: IV drip at 5–10 μg/min, USE NON-PVD tubing
  
• Nitropaste: 1–2 in transdermal
  
• Thrombolytics: See “Reperfusion Therapy, Cardiac,” for dosing
  

FOLLOW-UP