Acute coronary syndrome

The acute coronary syndrome (ACS) is the development of chest pain of cardiac nature, often but not exclusively associated with an abnormal electrocardiogram (ECG). It is the most common presentation of myocardial infarction (heart attack), and investigations are aimed at confirming this pathology. Treatment depends largely on the findings on the ECG. It is a very common cause for emergency room attendance.

It is largely synonymous with unstable angina, as opposed to 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 or only partially respond to nitrate drugs (such as glyceryl trinitrate). Exertional angina that occurs at worsening rate ("crescendo angina") is similarly regarded as "unstable".

Symptoms

Acute coronary syndrome is a clinical diagnosis, i.e. based on the medical history and physical examination it is the doctor's impression that the pain may originate from the heart. If the pain is severe, close monitoring and symptomatic treatment may already be given before all investigations are complete. Two common mnemonic is in use for these situations: MOVE (monitor, oxygen, venous access, ECG) and MONA (morphine, oxygen, nitrate, aspirin).

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).

Treatment

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), 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 tube is passed up a large artery to identify blockages in the coronaries, with angioplasty and usually a stent insertion if a blockage is found.

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.

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.