Practice Essentials
Unstable angina belongs to the spectrum of clinical presentations referred to collectively as acute coronary syndromes (ACSs), which also includes ST-segment elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI).
Unstable angina is considered to be an ACS in which there is myocardial ischemia without detectable myocardial necrosis (ie, cardiac biomarkers of myocardial necrosis —such as creatine kinase MB isozyme, troponin, myoglobin—are not released into the circulation). See the image below.
Pathogenesis of acute coronary syndromes.
Signs and symptoms
With unstable angina, symptoms may (1) occur at rest; (2) become more frequent, severe, or prolonged than the usual pattern of angina; (3) change from the usual pattern of angina; or (4) not respond to rest or nitroglycerin.
Symptoms of unstable angina are similar to those of myocardial infarction (MI) and include the following:
Chest pain or pressure
Pain or pressure in the back, neck, jaw, abdomen, shoulders or arms
Sweating
Dyspnea
Nausea, vomiting
Dizziness or sudden weakness
Fatigue
The patient’s history and diagnostic testing are generally more sensitive and specific for unstable angina than the physical examination, which may be unremarkable. Examination in a patient with unstable angina may yield the following findings:
Diaphoresis
Tachycardia or bradycardia
Transient myocardial dysfunction (eg, systolic blood pressure < 100 mm Hg or overt hypotension, elevated jugular venous pressure, dyskinetic apex, reverse splitting of S2, presence of S3 or S4, new or worsening apical systolic murmur, or rales or crackles)
Peripheral arterial occlusive disease (eg, carotid bruit, supraclavicular or femoral bruits, or diminished peripheral pulses or blood pressure)
See Presentation for more detail.
Diagnosis
The following laboratory studies are recommended in the evaluation of a patient with unstable angina:
12 lead electrocardiogram
Serial cardiac biomarker assays (eg, creatine kinase MB isoenzyme [CK-MB], troponin I or T)
Complete blood count (CBC) with hemoglobin level
Serum chemistry panel (including magnesium and potassium)
Lipid panel
Other tests that may be used to assess patients include the following:
Creatinine level
Exercise testing when patients are stable
The following imaging studies may be used to assess patients with suspected unstable angina:
Chest radiography
Echocardiography
Computed tomography angiography
Magnetic resonance angiography
Single-photon emission computed tomography
Magnetic resonance imaging
Myocardial perfusion imaging
See Workup for more detail.
Management
Management is directed toward (1) reducing myocardial oxygen demands; (2) improving myocardial oxygen supply; and (3) assessing the patient’s risk of progression to MI or having a complication related to treatment.
Patients with unstable angina require admission to the hospital for bed rest with continuous telemetry monitoring. One should obtain intravenous (IV) access, and provide supplemental oxygen if evidence of desaturation is noted. The course of unstable angina is highly variable and potentially life-threatening; therefore, quickly determine whether the initial treatment approach should use an invasive (surgical management) or a conservative (medical management) strategy.
The following medications are used in the management of unstable angina:
Antiplatelet agents (eg, aspirin, clopidogrel)
Lipid-lowering statin agents (eg, simvastatin, atorvastatin, pitavastatin, and pravastatin)
Cardiovascular antiplatelet agents (eg, tirofiban, eptifibatide, and abciximab)
Beta blockers (eg, atenolol, metoprolol, esmolol, nadolol, and propranolol)
Anticoagulants (eg, heparin or low-molecular-weight heparins [LMWHs] [eg, enoxaparin, dalteparin, and tinzaparin])
Thrombin inhibitors (eg, bivalirudin, lepirudin, desirudin, and argatroban)
Nitrates (eg, nitroglycerin IV)
Calcium channel blockers (diltiazem, verapamil, or nifedipine)
Angiotensin-converting enzyme inhibitors (ACEIs) (eg, captopril, lisinopril, enalapril, and ramipril)
Surgical intervention in unstable angina may include the following:
Cardiac catheterization
Revascularization
See Treatment and Medication for more detail.