Acute coronary syndromes

	Acute Coronary Syndrome Chapters
Heart Attack Patient Information
Unstable Angina Patient Information
Overview
Classification Unstable Angina Non-ST Elevation Myocardial Infarction ST Elevation Myocardial Infarction
Causes
Differential Diagnosis
Treatment
AHA/ACC Guidelines for Acute Coronary Syndrome
Guideline for Risk Stratification in ACS
Guideline for Pre-Hospital Evaluation and Care
Guidelines for Initial Management of ACS
Guidelines for Patients with Atrial Fibrillation Complicating ACS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S [2]; Tarek Nafee, M.D. [3]; Sabawoon Mirwais, M.B.B.S, M.D.[4]

Synonyms and keywords: ACS

Overview

Acute coronary syndrome (ACS) refers to any group of symptoms attributed to obstruction of the coronary arteries. 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. Acute coronary syndrome usually occurs as a result of one of three problems: ST-elevation myocardial infarction (30%), non ST-elevation myocardial infarction (25%), or unstable angina (38%). These types are named according to the appearance of the electrocardiogram. There can be some variation as to which forms of myocardial infarction (MI) are classified under acute coronary syndrome. ACS should be distinguished from stable angina, which is chest pain that develops during exertion and resolves at rest. New-onset angina however should be considered as a part of acute coronary syndrome, since it suggests a new problem in a coronary artery. Though ACS is usually associated with coronary thrombosis, it can also be associated with cocaine use. Cardiac chest pain can also be precipitated by anemia, bradycardias or tachycardias.

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, acute coronary syndrome is 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)