Acute coronary syndrome (ACS) is when plaque build up within the coronary arteries causes reduced blood flow to the heart.

In early stages this may 'only' cause symptoms ie anginal pain, in extreme cases this will cause death of cardiac tissue and death.

Myocardial tissue is not able to regenerate effectively, and damage is permanent. If the area of damage is large there is poor long term outlook.

There are three types of acute coronary syndrome which reflect increasing degrees of heart damage: Unstable angina, non-ST elevated myocardial infarction, and ST elevated myocardial infarction.

Angina

• Stable: Reduced blood flow is causing chest pain, but permanent tissue damage has not yet occurred. Symptoms manifest during physical exertion or stress. Stable angina is not considered ACS.
• Unstable: When anginal pains occur even at rest the patient this indicates ACS and higher risk of an MI.

Myocardial Infarction (MI)

Near or total blockage of a coronary artery causes cardiac cells to be deprived of oxygen after which they will start dying (ischaemia). The area of damage becomes increasingly larger until blood flow can be restored, this is why the blockage needs to be removed as quickly as possible. The most effective way to remove the blockage is manually (eg PCI).

Two main tests to confirm MI has occured:

• Blood tests - detect the presence of cardiac cell enzymes (troponins) released into the blood stream by dying cardiac cells
• Abnormal ECG readings (see illustration below) - A Non-ST elevated MI (NSTEMI) may be considered to be less severe than an ST-elevated MI (STEMI), but NSTEMI is still a serious condition, and treated similarly to STEMI eg with PCI.

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The most effective way of removing the blockage is by medical procedure. PCI is a procedure where a wire with a balloon is threaded into the coronary artery, the balloon is inflated to open it up and then a tubular wire mesh called a stent is inserted to keep it open. A drug eluting stent releases medication to prevent growth of scar tissue from re-occluding the artery. Check out the linked video:

PCI: You Tube video

US Pharmacist drug eluting stent

PCI is an invasive procedure but not considered to be a surgical procedure.

Alternative to PCI is a coronary by-pass graft (CABG) (also known as a heart by pass) which is a surgical procedure.

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The 80% occlusion of the left anterior descending artery is determined via angiography, an procedure which uses contrast dye and X-ray imaging.