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Potentially life-threatening emergency
Acute coronary syndrome
Other Resources UpToDate PubMed
Potentially life-threatening emergency

Acute coronary syndrome

Contributors: Joel Moll MD, Alex Robinson MD, Paritosh Prasad MD, Ryan Hoefen MD, PhD, Bruce Lo MD
Other Resources UpToDate PubMed


Emergent Care / Stabilization:
Airway, breathing, and circulation (ABCs), obtain and interpret 12-lead ECG within 10 minutes of arrival to identify a STEMI and need for emergent revascularization, establish intravenous (IV) access, place patient on cardiac monitor with continuous pulse oximetry, have resuscitation equipment available, consider serial ECGs, obtain troponin, aspirin load if no contraindications, and nitroglycerin, oxygen, and analgesia as indicated.

Diagnosis Overview:
Acute coronary syndrome (ACS) represents a spectrum of clinical diseases that result from an acute mismatch of myocardial oxygen supply and demand leading to myocardial ischemia or infarction. ACS includes ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), and unstable angina (UA). When the severity and duration of ischemia are sufficient to cause necrosis of myocardial tissue, the result is acute myocardial infarction (AMI). AMI is further divided into multiple subtype classifications: When considering ACS, type 1 AMI is the result of a coronary event with acute occlusion followed by thrombus formation and vasospasm. Type II AMI is the result of secondary ischemia due to increased oxygen demand or decreased supply.

The most prominent presenting symptom of ACS is usually diffuse chest discomfort, often described as a crushing pressure-like sensation. Presenting symptoms of ACS are variable and can include combinations of chest pain, pressure, heaviness, or discomfort that can radiate to the upper extremities, neck, abdomen, back, or jaw. Other associated symptoms can include diaphoresis, nausea, vomiting, shortness of breath, lightheadedness, confusion, presyncope, syncope, and fatigue. Vague associated symptoms can be subtle and without chest pain, especially in women, elderly individuals, and those with comorbid conditions such as diabetes.

ACS is most commonly due to coronary artery atherosclerosis, the long-term result of a cascade of chronic inflammatory processes that lead to the development of plaques. The fibrous cap over the plaques may be unstable and can rupture, leading to a platelet-rich thrombosis, which can partially or completely obstruct blood flow. Usually, ischemic symptoms at rest develop when coronary vessel stenosis exceeds 95% obstruction. Risk factors for atherosclerotic disease include hypertension, hyperlipidemia, diabetes, smoking, increased weight, increased age, male sex, renal insufficiency, sedentary lifestyle, Western diet, and family history of atherosclerotic disease. In the United States, ACS is most common in the sixth decade of life and has a male-to-female ratio of 3:2. Approximately 900 000 Americans experience AMI per year, and 30% of these individuals die within 30 days.

Less common causes of arterial obstruction that can result in ACS include embolic events, vasospasm, and coronary artery dissection. ACS may also occur as a result of diffuse myocardial ischemia and infarction in the setting of noncardiac disease such as severe anemia, hypoxemia, or sepsis. Rarely, acute rupture of the ventricular wall can occur in late-presenting cases of myocardial infarction.

ACS is a major cause of morbidity and mortality throughout the world; however, while overall cases have declined, cases of NSTEMI have risen due to increasingly sensitive troponin assays.

ACS represents a spectrum of disease severity that is differentiated by ECG findings and serum cardiac enzyme (troponin) levels:
  • STEMI – New ST segment elevation at the J point in 2 contiguous leads on ECG and elevated cardiac enzyme levels.
  • NSTEMI – Elevated cardiac enzyme levels without ST elevations. New horizontal or downsloping ST depressions and/or T-wave inversions in 2 or more contiguous leads may or may not be present on ECG.
  • UA – Chest pain and/or other symptoms of ischemia that are new, worsening, or occurring at rest in the absence of abnormal cardiac enzyme levels. ST-segment depressions and T-wave inversions may or may not be present on ECG. This is distinguished from stable angina, in which chronic coronary artery disease causes chest discomfort that is provoked by exertion or stress and resolves spontaneously with rest or nitroglycerin in a predictable manner.


I20.0 – Unstable angina
I21.9 – Acute myocardial infarction, unspecified

394659003 – Acute coronary syndrome

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

Other cardiac causes of chest pain:
  • Microvascular angina
  • Pericarditis – Sharp pain, positional (improved with leaning forward), recent illness or myocardial infarction (or other risk factors), pericardial friction rub, diffuse ST elevations on ECG.
  • Aortic dissection – Tearing chest pain, hypotension, tachycardia, CT; can be diagnosed with CT angiogram of the chest and abdomen. The dissection may involve the coronary artery, causing a STEMI on ECG. 
  • Coronary vasospasm
  • Spontaneous coronary artery dissection
  • Takotsubo cardiomyopathy
  • Congestive heart failure
  • Mitral valve disease (eg, Mitral valve prolapse, Mitral regurgitation, or Mitral valve stenosis)
  • Substance related (eg, Cocaine-related cardiomyopathy- or stimulant-related ischemia or cardiomyopathy)
  • Expanding aortic aneurysm – Similar risk factors to ACS can be seen on ultrasound or CT. See Abdominal aortic aneurysm.
Pulmonary causes:
  • Pulmonary embolism – Pleuritic chest pain, tachycardia, shortness of breath, syncope, evidence of right heart strain on ECG, CT angiogram of the chest; presentation can also be atypical. 
  • Pneumothorax / Hemothorax
  • Pneumonia – Pleuritic chest pain, cough, fever. See Community-acquired pneumonia.
  • Acute bronchitis
  • Malignancy (see, eg, Lung cancer)
  • Pleurisy
  • Sarcoidosis
  • Acute chest syndrome
  • Pulmonary hypertension
Gastrointestinal causes:
  • Gastroesophageal reflux disease – Burning pain, pain after eating large or spicy meals, and pain on abdominal examination.
  • Peptic ulcer disease
  • Esophageal motility disorder
  • Esophagitis
  • Eosinophilic esophagitis
  • Hiatal hernia
  • Spontaneous rupture of esophagus
  • Referred pain from abdominal viscera (eg, acute Acute cholecystitis, Acute pancreatitis) – Can see abnormal liver function tests and pancreatic enzyme levels.
  • Sickle cell acute pain crisis
Musculoskeletal causes:
  • Costochondritis – Sharp, localized, reproducible, history of traumatic injury
  • Rheumatic diseases (eg, Rheumatoid arthritis, Fibromyalgia)
  • Chest wall trauma
Psychiatric causes:
  • Panic disorder / Generalized anxiety disorder 
Infectious causes:
  • Herpes zoster (shingles) – Look for vesicular rash in dermatomal pattern; pain may precede the development of the rash.

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Management Pearls

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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Last Reviewed:08/21/2022
Last Updated:11/29/2022
Copyright © 2024 VisualDx®. All rights reserved.
Potentially life-threatening emergency
Acute coronary syndrome
A medical illustration showing key findings of Acute coronary syndrome (Prodromal Symptoms) : Chest pain, Fatigue, Malaise, Dyspnea
Copyright © 2024 VisualDx®. All rights reserved.