Acute Coronary Syndrome: Angina

Basics

Description

  • Chest discomfort, from imbalance of myocardial blood supply and oxygen requirements
  • Typically categorized as stable or unstable
  • Stable angina: Predictable, with exertion, and improves with rest
  • Unstable angina (UA): New onset, increase in frequency, duration or lower threshold for symptoms, at rest, or >20 min
  • UA associated with increased risk of transmural myocardial infarction (MI) and cardiac death
  • New high-sensitivity cardiac biomarkers blur boundaries between UA and NSTEMI

Etiology

  • Cardiac risk factors:
    • Age:
      • Men >35 yr
      • Postmenopausal in women
    • Hypercholesterolemia
    • HTN
    • Smoking
  • Atherosclerotic narrowing of coronary vessels:
    • Stable angina: Chronic and leads to imbalance of blood flow during exertion
    • UA: Acute disruption of plaque which can lead to worsening symptoms with exertion or at rest
  • Vasospasm: Prinzmetal angina, drug related (cocaine, amphetamines)
  • Microvascular angina or abnormal relaxation of vessels if diffuse vascular disease
  • Arteritis: Lupus, Takayasu disease, Kawasaki disease, rheumatoid arthritis
  • Anemia
  • Hyperbarism, carboxyhemoglobin elevation
  • Abnormal structure of coronaries: Post radiation, aneurysm, ectasia

Diagnosis

Signs And Symptoms

History

  • Chest pain:
    • Substernal pressure, heaviness, tightness, burning, or squeezing
    • Radiates to neck, jaw, left shoulder, or arm
  • Poorly localized, visceral pain
  • Anginal equivalents include:
    • Dyspnea
    • Epigastric discomfort
    • Weakness
    • Diaphoresis
    • Nausea/vomiting
    • Abdominal pain
    • Syncope (rare not to have concomitant typical anginal symptoms)
  • Symptoms usually reproduced by exertion, eating, cold exposure, emotional stress
  • Symptoms not usually positional or pleuritic
  • Usually relieved with rest or nitroglycerin
  • For stable angina often lasts more than a few seconds but <20 min and no changes in pattern of frequency of symptoms

Geriatric Considerations

  • Women, patients with diabetes, ethnic minorities, and those 65+ yr often with atypical symptoms
  • Prognosis is worse for people with atypical symptoms

Physical Exam

  • “Levine sign”: Clenched fist over chest
  • BP often elevated during symptoms
  • Physical exam often uninformative
  • Can look for S3/S4, papillary muscle dysfunction with mitral regurgitation or new murmur, diminished peripheral pulses

Essential Workup

  • ECG:
    • Standard 12 lead should be obtained and read within 10 min of presentation for patients with acute chest pain
    • Helpful in detecting acute MI, less so UA
    • Important to compare to prior ECG if available
    • New ST changes or TWI suspicious for UA:
      • T-wave flattening or biphasic T waves
      • ≤1-mm ST depression 80 msec from the J point, is characteristic in UA
      • Can see evidence of old ischemia, strain or infarct, such as old TWI, Q wave, ST depression
      • Serial ECGs helpful in distinguishing unstable from stable angina
      • A single ECG for acute MI is about 60% sensitive and 90% specific
    • ECG can also be helpful to diagnose other causes of chest pain:
      • Pericarditis: Diffuse ST elevations, then TWIs and pulse rate depression
      • Pulmonary embolus S1Q3T3 pattern, unexplained tachycardia, and signs of right heart strain
ALERT

Patients with normal or nonspecific ECGs have a 1–5% incidence of AMI and 4–23% incidence of UA

Diagnostic Tests And Interpretation

Lab

  • In stable angina, cardiac enzymes not indicated, but if history suspicious for acute MI, these should be obtained
  • Troponin I or T:
    • Troponin peaks in 12 hr, return to baseline 7–10 d
  • CK-MB:
    • Useful when troponin is ambiguous, ie, in patients with renal insufficiency
    • CK-MB peaks 12–24 hr, return to baseline in 2–3 d
  • High-sensitivity troponins changing positive threshold and timing of rule-out:
    • High-sensitivity troponins elevate earlier at lower thresholds but often need repeat measurements and base determinations of disease on change in measurements
  • Hematocrit (anemia increases risk of ischemia)
  • Coagulation profile
  • Electrolytes, especially Cr and K+
  • The HEART score for risk stratification:
    • History (highly suspicious – 2 points, moderately suspicious – 1 point, slightly suspicious – 0 points)
    • ECG (significant ST-depression – 2 points, nonspecific repolarization disturbance – 1 point, normal – 0 points)
    • Age (≥65 yr – 2 points, >45–<65 yr – 1 point, ≤45 yr – 0 points)
    • Risk factors (>3 risk factors or history of atherosclerotic disease – 2 points, 1 or 2 risk factors – 1 point, no known risk factors – 0 points)
    • Troponin (≥3× normal limit – 2 points, >1–<3× normal limit – 1 point, ≤normal limit – 0 points)
    • Patients with ≤3 score considered low-risk
    • Low-risk patients may be ruled out with single negative high-sensitivity troponin

Imaging

  • CXR:
    • Usually nonrevealing
    • May show cardiomegaly, or pulmonary edema; CHF can be suggestive of UA
    • May be helpful in identifying other etiologies such as pneumonia, pneumothorax, or aortic dissection
  • Coronary CTA:
    • Good for low-risk patients with no known CAD to rule out ischemia as cause of pain if no coronary stenosis
    • “Triple rule-out” for ACS, PE, and aortic dissection
  • Bedside echo: To detect wall motion abnormalities and other etiologies of shock, pericardial effusion, pneumothorax
  • Tc-99 sestamibi (rest): Radionucleotide whose uptake by myocardium is dependent on perfusion

Diagnostic Procedures/Surgery

  • Exercise stress testing:
    • Not appropriate for active chest pain with moderate to high likelihood of ischemia
    • Low yield of detecting clinically significant coronary disease in low-risk patients as part of ED workup
    • Imaging stress test (sestamibi, thallium, or echo) if baseline ECG abnormalities
  • Other imaging modalities including MRI, PET have also been used
  • Coronary angiography:
    • Gold standard for diagnosis for CAD

Differential Diagnosis

  • Anxiety and panic disorders
  • Aortic dissection
  • Biliary colic
  • Costochondritis
  • Esophageal reflux
  • Esophageal spasm
  • Esophagitis
  • GERD
  • Herpes zoster
  • Hiatal hernia
  • Mitral valve prolapse
  • Musculoskeletal chest pain
  • MI
  • Myocarditis
  • Nonatherosclerotic causes of cardiac ischemia:
    • Coronary artery spasm
    • Coronary artery embolus
    • Congenital coronary disease
    • Coronary dissection
    • Valvular disease: AS, AI, pulmonary stenosis, mitral stenosis
    • Congenital heart disease
  • Peptic ulcer disease
  • Pericarditis
  • Pneumonia
  • Psychogenic
  • Pneumothorax
  • Pulmonary embolism

Treatment

Prehospital

  • IV access
  • Aspirin
  • Oxygen
  • Vital signs and oxygen saturation
  • Cardiac monitoring
  • 12-lead ECG, if possible
  • Sublingual nitroglycerin

Initial Stabilization/Therapy

  • IV access
  • Oxygen
  • Cardiac monitoring
  • Vital signs and continuous oxygen saturation

Ed Treatment/Procedures

  • All patients with chest pain in which cardiac ischemia is a consideration should receive an aspirin upon arrival to the ED
  • Sublingual nitroglycerin: If symptoms persist after 3 sublingual doses, maybe suggestive of UA, AMI, or noncardiac etiology:
    • However, GERD is more common in the ED and also relieved by nitroglycerin
  • Pain control
  • Anticoagulation

Medication

First Line

  • Aspirin: 325 mg or 81 mg × 4 PO (chewed)
  • In patients with aspirin allergy can give clopidogrel (Plavix) 300–600 mg PO, can also consider prasugrel 60 mg PO or ticagrelor
  • Dual antiplatelet therapy should be given to patients with UA at medium to high risk who have been selected to have invasive strategy such as catheterization or surgery
  • Nitroglycerin:
    • 0.4 mg sublingual
    • 5–10 mcg/min IV, titrating to effect
    • 1–2 in of nitro paste
    • Hold for low BP or if concern for preload dependence (RV infarct: Q in II, III, aVF; STE in right-sided V3, V4)
    • Beware if patient has history of erectile dysfunction and use of phosphodiesterase inhibitors like sildenafil (Viagra) or tadalafil (Cialis) in last 48 hr
  • Morphine:
    • 4 mg IV, titrate to relief of pain assuming no respiratory depression and SBP >90
    • Higher risk of death and adverse events in NSTEMI
  • Consider β-blocker:
    • Metoprolol: 25–50 mg PO or 5 mg IV q5–15 min for refractory HTN and tachycardia
    • Contraindicated in active reactive airway disease, active CHF, bradycardia, hypotension, heart block, cocaine use
    • Does not necessarily need to be given in ED, suggested benefit within 24 hr of AMI

Second Line

  • Can vary by institution, recommend conferring with inpatient cardiologist regarding anticoagulation
  • Heparin: 60-U/kg IV bolus, then 12 U/kg/hr (goal PTT 50–70)
  • Enoxaparin: 1 mg/kg SC q12 or q24 if Cr clearance <30 mL/min
  • Glycoprotein IIb/IIIa inhibitors:
    • Eptifibatide (Integrilin): 180-ug/kg bolus IV over 1–2 min, then 2 ug/kg/min up to 72 hr
    • Tirofiban (Aggrastat): 0.4 ug/kg/min for 30 min, then 0.1 ug/kg/min for 48–108 hr
    • Abciximab (ReoPro): 0.25-mg/kg IV bolus, then 0.125 ug/kg/min
    • Bivalirudin, fondaparinux
  • Patients at high risk for bleeding include the elderly, female, anemic, CKD
  • For stable angina, management consists of preventative therapies including aspirin, blood pressure control (β-blocker, calcium channel blocker, long-acting nitrates) and lifestyle modification (weight loss, statin or other lipid lowering therapies, decreased fat/sugar intake, smoking cessation)

Follow-Up

Disposition

Admission Criteria

  • Patients with UA require admission to the hospital
  • Early intervention with cardiac catheterization likely decreases mortality in patients with elevations in cardiac enzymes, persistent angina, or hemodynamic instability
  • Patients with unclear diagnosis likely would benefit from admission to ED observation unit or hospital admission for serial cardiac enzymes, ECG, and stress testing/catheterization

Discharge Criteria

Patients with stable angina

Follow-Up Recommendations

Patients with stable angina should follow up with their PCP and a cardiologist

Pearls And Pitfalls

  • History is the most important factor in differentiating unstable from stable angina
  • All patients with chest pain or symptoms concerning for a cardiac etiology should have an immediate ECG, and serial ECGs are essential for ACS workup
  • A single high-sensitivity troponin may rule out ACS in low-risk patients
  • Women, patients with diabetes, ethnic minorities, and patients 65+ yr require a low threshold for ACS workup and often have atypical presentations
  • It is important to work with the inpatient cardiologist/interventionalist regarding anticoagulation regimen choice as this may vary by institution

Additional Readings

  1. Bhatt DL, Lopes RD, Harrington RA. Diagnosis and treatment of acute coronary syndromes: A review. JAMA. 2022;327(7):662–675. Erratum in: JAMA. 2022;327(17):1710.  [PMID:35166796]
  2. Gulati M, Levy PD, Mukherjee D, et al. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. J Cardiovasc Comput Tomogr. 2022;16(1):54–122.  [PMID:34955448]
  3. Laureano-Phillips J, Robinson RD, Aryal S, et al. HEART score risk stratification of low-risk chest pain patients in the emergency department: A Systematic Review and Meta-Analysis. Ann Emerg Med. 2019;74(2):187–203.  [PMID:30718010]
  4. Lazar DR, Lazar FL, Homorodean C, et al. High-sensitivity troponin: A review on characteristics, assessment, and clinical implications. Dis Markers. 2022;2022:9713326.  [PMID:35371340]
  5. Walls RM, Hockberger RS, Gausche-Hill M, Erickson TB, Wilcox SR, eds. Chest pain. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 10th ed. Mosby Elsevier; 2022.

See Also (Topic, Algorithm, Electronic Media Element)

Authors

Margaret J. Lin-Martore

Shamai A. Grossman