What is Acute Coronary Syndrome?
Acute Coronary Syndrome (ACS) is a situation of medical emergency that refers to a group of clinical conditions compatible with acute myocardial ischemia (AMI) and/or infarction. ACS occurs when the blood supply to the heart is blocked due to destabilization of a previously stable atherosclerotic plaque.2,3
There are three classifications according to the presence of Electrocardiography (ECG) abnormalities and Myocardial Infarction (MI):2,3
- Unstable angina;
- NSTEMI (non ST-segment-elevation MI);
- STEMI (ST-segment-elevation MI).2,3
How is AMI diagnosed?
Myocardial infarction (MI), commonly known as a heart attack, is defined pathologically as the irreversible death of myocardial cells caused by ischemia. Clinically, MI is a syndrome that can be recognized by a set of symptoms, chest pain being the hallmark of these symptoms in most cases, supported by biochemical laboratory changes, electrocardiographic (ECG) changes, or findings on imaging modalities able to detect myocardial injury and necrosis.
The Fourth Universal Definition of Myocardial infarction proposes that the term acute myocardial infarction(AMI) should be used only when there is acute myocardial damage with clinical evidence of acute myocardial ischemia.4
The diagnosis of AMI requires elevation or drop in troponin values and the presence of at least one of the following criteria:
- Symptoms of acute myocardial ischemia;
- New ischemic electrocardiographic (EKG) findings;
- Development of new abnormal Q waves;
- Imaging evidence of loss of viable myocardium or abnormal motion of any of the walls due to ischemic cause; or
- Identification of a coronary thrombus on angiography.
Should this not be the case, then the proposal is to refer only to myocardial damage.4 High-sensitivity (hs)–cTn assays are recommended for routine clinical use.5 Myocardial injury is defined as being present when blood levels of cTn are increased above the 99th percentile upper reference limit (URL).5,6 The injury may be acute, as evidenced by a newly detected dynamic rising and/or falling pattern of cTn values above the 99th percentile URL, or chronic, in the setting of persistently elevated cTn levels.