Acute coronary syndromes
Synonyms and keywords: acute coronary syndrome, acute coronary syndromes, ST-elevation myocardial infarction, Non-ST-segment elevation acute coronary syndrome, unstable angina, STEMI, UA, , NSTEMI, NSTE-ACS

# Overview
Acute coronary syndrome (ACS) refers to a spectrum of conditions resulting from acute myocardial ischemia and/or infarction that is most often due to an
abrupt reduction in coronary blood flow. The most common symptom prompting diagnosis of ACS is chest pain, often radiating to the left arm or angle of the jaw, pressure-like in character, and associated with nausea and sweating. ACS should be distinguished from stable angina, which is chest pain that develops during exertion and resolves at rest. Traditionally, ACS has been classified into non-ST-elevation myocardial infarction (NSTEMI), ST-elevation MI (STEMI), and unstable angina. Unstable angina is differentiated from NSTEMI by the absence of elevated cardiac biomarkers. The basic pathology in both conditions involves a non-occlusive thrombus formation from a previously disrupted atherosclerotic plaque causing an inadequate blood supply to the heart muscle. Though ACS is usually associated with coronary thrombosis, it can also be associated with other causes such as cocaine use. Cardiac chest pain can also be precipitated by anemia, bradycardias or tachycardias.

# Classification
- Traditionally, ACS has been classified into:
Unstable angina (UA)
Non-ST-segment elevation myocardial infarction (NSTEMI)
ST-segment elevation myocardial infarction (STEMI).
- Unstable angina (UA)
- Non-ST-segment elevation myocardial infarction (NSTEMI)
- ST-segment elevation myocardial infarction (STEMI).
- According to this classification, unstable angina was defined as clinical and electrocardiographic (ECG) evidence of myocardial ischemia in the absence of an elevated troponin level.
- However, the widespread use of the high-sensitivity troponin assays made UA and NSTEMI indistinguishable since it was shown that almost all patients previously named UA actually have increased high-sensitivity troponin levels.
- In other words, it is very unlikely that patients with clinical and ECG evidence of myocardial ischemia have normal high-sensitivity troponin levels. 
- Consequently, in recent guidelines, the acute coronary syndromes are classified into two broad categories:  
Non-ST-segment elevation acute coronary syndrome (NSTE-ACS), encompassing :
Non-ST-segment elevation myocardial infarction (NSTEMI)
Unstable angina
ST-segment elevation myocardial infarction (STEMI)
- Non-ST-segment elevation acute coronary syndrome (NSTE-ACS), encompassing :
Non-ST-segment elevation myocardial infarction (NSTEMI)
Unstable angina
- Non-ST-segment elevation myocardial infarction (NSTEMI)
- Unstable angina
- ST-segment elevation myocardial infarction (STEMI)
- Therefore, acute coronary syndromes can be classified as follows:

# Defining Lesion Severity. 2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization. (Please do not edit).

## Angiography to Define Anatomy and Assess Lesion Severity
The standard procedure for defining coronary anatomy and assessing the degree of coronary artery stenosis is still coronary angiography.
- Severe Stenosis:  diameter stenosis severity of 70% for non-left main disease and 50% for left main illness .
- A diameter stenosis severity of 40% to 69% is referred to as an angiographically intermediate coronary stenosis, and it usually necessitates further examination to determine its physiological significance .
- Longer  lesions may cause more ischemia than a single severe lesion .

# Causes
- ACS is characterized by a sudden imbalance between myocardial oxygen consumption and demand, which is usually the result of coronary artery obstruction. 
- The most common causes of coronary artery obstruction are:
Atherosclerotic plaque rupture and subsequent coronary thrombus
- Atherosclerotic plaque rupture and subsequent coronary thrombus
- Other conditions may also cause an imbalance, including:
Excessive myocardial oxygen demand (in the setting of a stable flow-limiting lesion)
Coronary artery spasm causing vasospastic (Prinzmetal) angina
Coronary embolism
Coronary arteritis
Noncoronary causes of myocardial oxygen supply-demand mismatch :
Hypotension
Severe anemia
Hypertension
Tachycardia
Hypertrophic cardiomyopathy
Severe aortic stenosis
Nonischemic myocardial injury:
Myocarditis
Cardiac contusion
Cardiotoxic drugs
Multifactorial causes:
Stress cardiomyopathy (Takotsubo cardiomyopathy)
Pulmonary embolism
Severe heart failure (HF)
Sepsis
- Excessive myocardial oxygen demand (in the setting of a stable flow-limiting lesion)
- Coronary artery spasm causing vasospastic (Prinzmetal) angina
- Coronary embolism
- Coronary arteritis
- Noncoronary causes of myocardial oxygen supply-demand mismatch :
Hypotension
Severe anemia
Hypertension
Tachycardia
Hypertrophic cardiomyopathy
Severe aortic stenosis
Nonischemic myocardial injury:
Myocarditis
Cardiac contusion
Cardiotoxic drugs
- Hypotension
- Severe anemia
- Hypertension
- Tachycardia
- Hypertrophic cardiomyopathy
- Severe aortic stenosis
- Nonischemic myocardial injury:
Myocarditis
Cardiac contusion
Cardiotoxic drugs
- Myocarditis
- Cardiac contusion
- Cardiotoxic drugs
- Multifactorial causes:
Stress cardiomyopathy (Takotsubo cardiomyopathy)
Pulmonary embolism
Severe heart failure (HF)
Sepsis
- Stress cardiomyopathy (Takotsubo cardiomyopathy)
- Pulmonary embolism
- Severe heart failure (HF)
- Sepsis
For a complete list of causes for UA click here, for NSTEMI click here, and for STEMI click here.

# Differentiating Acute coronary syndromes from other Diseases
- View the page on diagnosis using the clinical prediction rule for ACS for more detail.
- To view the detailed differential diagnosis of chest pain click here.
- Acute Coronary Syndrome (ACS) may be differentiated from other diseases as follows:     
The following table summarizes the significant history, and diagnostic test findings that will help differentiate the acute coronary syndromes from one another, as well as from other coronary artery diseases:

# SYNTAX Score to Calculate the Complexity of Coronary Artery Lesions. 2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization. (Please do not edit.)

## Differential Diagnoses of Acute Coronary Syndromes in the Setting of Chest Pain

# Treatment
- To view the detailed treatment of Unstable angina/NSTEMI click here.
- To view the detailed treatment of STEMI  click here.

# 2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization. Recommendations  to prefer PCI or CABG (Please do not edit)

## Patients With Complex Disease

## Patients with Diabetes

## Patients With Previous CABG

## Dual antiplatelet therapy (DAPT)

## Revascularization in Pregnant Patients

## Revascularization in Older Patients

## Revascularization in Patients With Chronic Kidney Disease

## Revascularization in Patients Before Noncardiac Surgery

## Revascularization in Patients to Reduce Ventricular Arrhythmias

## Revascularization in Patients With Spontaneous coronary artery dissection (SCAD)

## Revascularization in Patients With Cardiac Allografts

# 2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization (Please do not edit). RECOMMENDATIONS FOR ADDRESSING PSYCHOSOCIAL FACTORS AND LIFESTYLE CHANGES AFTER REVASCULARIZATION

## Cardiac Rehabilitation and Education

## Smoking Cessation in Patients After Revascularization

## Psychological Interventions in Patients After Revascularization

# 2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization (Please do not edit). Revascularization Outcomes

## Assessment of Outcomes in Patients After Revascularization