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 (USA), Non-ST Segment Elevation Myocardial Infarction (NSTEMI), and ST Segment Elevation Myocardial Infarction (STEMI), commonly referred to as a heart attack.
Signs and Symptoms
The signs and symptoms of ACS may include:
- chest pain
- shortness of breath
- diaphoresis (sweating)
- anxiety or implending sense of doom
- a feeling of being acutely ill
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, is worsening, and does not respond or only partially responds to nitrate drugs (such as glyceryl trinitrate). Exertional angina that occurs at worsening rate ("crescendo angina") is similarly regarded as "unstable".
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).
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), thrombolysis 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.
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.
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.