Acute coronary syndrome
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An acute coronary syndrome (ACS) is a set of signs and symptoms suggestive of sudden cardiac ischemia, usually caused by disruption of atherosclerotic plaque in an epicardial coronary artery. The acute coronary syndromes include Unstable Angina (UA), Non-ST Segment Elevation Myocardial Infarction (NSTEMI), and ST Segment Elevation Myocardial Infarction (STEMI), commonly referred to as a heart attack.
ACS should be distinguished from stable angina, which develops during exertion and resolves at rest. In contrast with stable angina, unstable angina occurs suddenly, often at rest or with minimal exertion, or at lesser degrees of exertion than the individual's previous angina ("crescendo angina"). New onset angina is also considered unstable angina, since it suggests a new pathophysiologic process in the coronary artery.
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[edit] Signs and Symptoms
The signs and symptoms of ACS may include:
- chest pain
- shortness of breath
- nausea
- vomiting
- diaphoresis (sweating)
- palpitations
- anxiety or sense of impending doom
- a feeling of being acutely ill
[edit] Diagnosis
As it is only one of the many potential causes of chest pain, the patient usually has a number of tests in the emergency department, such as a chest X-ray, blood tests (including myocardial markers such as troponin I or T, and a D-dimer if a pulmonary embolism is suspected), and telemetry (monitoring of the heart rhythm).
[edit] Cardiac Biomarkers
According to Lemos, the use of cardiac markers can be divided into two applications; [1]
- Diagnosis
- Risk stratification
[edit] Biomarkers for Diagnosis
The aim of diagnostic markers is to identify patients with ACS even when there is no evidence of myocyte necrosis.
- Ischemia-Modified Albumin (IMA) - In cases of Ischemia - Albumin undergoes a conformational change and loses its ability to bind transitional metals (copper or cobalt). IMA can be used to assess the proportion of modified albumin in ischemia. Its use is limited to ruling out ischemia rather than a diagnostic test for the occurrence of ischemia.
- Myeloperoxidase (MPO) - The levels of circulating MPO, a leukocyte enzyme, elevate early after ACS and can be used as an early marker for the condition.
[edit] Biomarkers for Risk Stratification
The aim of prognostic markers is to reflect different components of pathophysiology of ACS. For example:
- Natriuretic peptide - Both B-type natriuretic peptide (BNP) and N-terminal Pro BNP can be applied to predict the risk of death and heart failure following ACS.
- Monocyte chemo attractive protein (MCP)-1 - has been shown in a number of studies to identify patients with a higher risk of adverse outcomes after ACS.
[edit] Treatment
[edit] STEMI
If the ECG confirms changes suggestive of myocardial infarction (ST elevations in specific leads, a new left bundle branch block or a true posterior MI pattern), thrombolytics may be administered or primary coronary angioplasty may be performed. In the former, medication is injected that stimulates fibrinolysis, destroying blood clots obstructing the coronary arteries. In the latter, a flexible catheter is passed via the femoral or radial arteries and advanced to the heart to identify blockages in the coronaries. When occlusions are found, they can be intervened upon mechanically with angioplasty and perhaps stent deployment if a lesion, termed the culprit lesion, is thought to be causing myocardial damage.
[edit] NSTEMI and NSTE-ACS
If the ECG does not show typical changes, the term "non-ST segment elevation ACS" is applied. The patient may still have suffered a "non-ST elevation MI" (NSTEMI). The accepted management of unstable angina and acute coronary syndrome is therefore empirical treatment with aspirin, heparin (usually a low-molecular weight heparin such as enoxaparin) and clopidogrel, with intravenous glyceryl trinitrate and opioids if the pain persists.
A blood test is generally performed for cardiac troponins twelve hours after onset of the pain. If this is positive, coronary angiography is typically performed on an urgent basis, as this is highly predictive of a heart attack in the near-future. If the troponin is negative, a treadmill exercise test or a thallium scintigram may be requested.
[edit] Prevention
Acute coronary syndrome often reflects a degree of damage to the coronaries by atherosclerosis. Primary prevention of atherosclerosis is controlling the risk factors: healthy eating, exercise, treatment for hypertension and diabetes, avoiding smoking and controlling cholesterol levels); in patients with significant risk factors, aspirin has been shown to reduce the risk of cardiovascular events. Secondary prevention is discussed in myocardial infarction.
[edit] References
- ^ James De Lemos, MD (2006). Cardiovascular Biomarkers for Acute Corony Syndromes Using a Multi-Marker Strategy.
