Acute Coronary Syndrome

Signs and symptoms

Atherosclerosis is the primary cause of ACS, with most cases occurring from the disruption of a previously nonsevere lesion. Complaints reported by patients with ACS include the following:

• Palpitations
• Pain, which is usually described as pressure, squeezing, or a burning sensation across the precordium and may radiate to the neck, shoulder, jaw, back, upper abdomen, or either arm
• Exertional dyspnea that resolves with pain or rest
• Diaphoresis from sympathetic discharge
• Nausea from vagal stimulation
• Decreased exercise tolerance

Physical findings can range from normal to any of the following:

• Hypotension: Indicates ventricular dysfunction due to myocardial ischemia, myocardial infarction (MI), or acute valvular dysfunction
• Hypertension: May precipitate angina or reflect elevated catecholamine levels due to anxiety or to exogenous sympathomimetic stimulation
• Diaphoresis
• Pulmonary edema and other signs of left heart failure
• Extracardiac vascular disease
• Jugular venous distention
• Cool, clammy skin and diaphoresis in patients with cardiogenic shock
• A third heart sound (S₃) and, frequently, a fourth heart sound (S₄)
• A systolic murmur related to dynamic obstruction of the left ventricular outflow tract
• Rales on pulmonary examination (suggestive of left ventricular dysfunction or mitral regurgitation)

Potential complications include the following:

• Ischemia: Pulmonary edema
• Myocardial infarction: Rupture of the papillary muscle, left ventricular free wall, and ventricular septum

Diagnosis

Updated guidelines for the management of non-ST-segment elevation ACS were released in 2020 by the European Society of Cardiology (ESC). ^[1] The updates place increased reliance on high-sensitivity cardiac troponin testing (hs-cTn) for diagnosis. The guidelines include the use of the CRUSADE risk score (Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation) of the ACC/AHA guidelines.

In the emergency setting, electrocardiography (ECG) is the most important diagnostic test for angina. ECG changes that may be seen during anginal episodes include the following:

• Transient ST-segment elevations
• Dynamic T-wave changes: Inversions, normalizations, or hyperacute changes
• ST depressions: These may be junctional, downsloping, or horizontal

Laboratory studies that may be helpful include the following:

• Creatine kinase isoenzyme MB (CK-MB) levels
• Cardiac troponin levels
• Myoglobin levels
• Complete blood count
• Basic metabolic panel

Diagnostic imaging modalities that may be useful include the following:

• Chest radiography
• Echocardiography
• Myocardial perfusion imaging
• Cardiac angiography
• Computed tomography, including CT coronary angiography and CT coronary artery calcium score

Management

Initial therapy focuses on the following:

• Stabilizing the patient’s condition
• Relieving ischemic pain
• Providing antithrombotic therapy

Pharmacologic anti-ischemic therapy includes the following:

• Nitrates (for symptomatic relief)
• Beta blockers (eg, metoprolol): These are indicated in all patients unless contraindicated

Pharmacologic antithrombotic therapy includes the following:

• Aspirin
• Clopidogrel
• Prasugrel
• Ticagrelor
• Glycoprotein IIb/IIIa receptor antagonists (abciximab, eptifibatide, tirofiban)

Pharmacologic anticoagulant therapy includes the following:

• Unfractionated heparin (UFH)
• Low-molecular-weight heparin (LMWH; dalteparin, nadroparin, enoxaparin)
• Factor Xa inhibitors (rivaroxaban, fondaparinux)

Additional therapeutic measures that may be indicated include the following:

• Thrombolysis
• Percutaneous coronary intervention (preferred treatment for ST-elevation MI)

Current guidelines for patients with moderate- or high-risk ACS include the following:

• Early invasive approach
• Concomitant antithrombotic therapy, including aspirin and clopidogrel, as well as UFH or LMWH