What is an ST Elevation Myocardial Infarction?

Solomon Branch

A myocardial infarction (MI), commonly referred to as a heart attack, occurs if a patient's coronary artery, an artery that wraps around the heart and provides the blood supply to it, is blocked to some extent by a blood clot. In an ST elevation myocardial infarction (STEMI), the patient's coronary artery is blocked completely. Once the blood supply is cut off, the heart tissue that was supplied blood by the coronary artery can, if left untreated, infarct, another word for die.

The anatomy of a heart attack.
The anatomy of a heart attack.

The movement of the heartbeat is often measured by an echocardiogram (ECG), a device that measures the electrical impulses coming from the heart and uses certain letters to label parts of the process. The “ST” in ST elevation myocardial infarction is the portion of the heartbeat where there should be little or no electrical activity; it usually appears as a flat line on a ECG chart. When a patient's ST segment is elevated, it indicates that there is electrical activity, and this in turn usually indicates that there is lack of blood flow to the heart.

The movement of the heartbeat is often measured by an ECG.
The movement of the heartbeat is often measured by an ECG.

There are two sub-categories of myocardial infarction: ST elevation myocardial infarction (STEMI) and Non-ST elevation myocardial infarction (NSTEMI). NSTEMI is the less serious of the two, as it indicates only a partial blockage of the coronary artery; STEMI is full blockage. Both STEMI and NSTEMI often have similar symptoms but are treated slightly differently, depending on the level of severity.

Typical symptoms for both STEMI and NSTEMI are sudden chest pain that usually radiates to the left side of the neck and down the left arm, shortness of breath, anxiety, and sweating. There might also be nausea, vomiting, and palpitations. There may also be no symptoms, or what’s known as a “silent” MI. This happens about 25 percent of the time. It is also important to know that women don’t usually have the same typical symptoms as men; they often have indigestion, weakness, nausea, and shortness of breath.

Treatment for an ST elevation myocardial infarction is usually with medications that breakdown the clot, a process known as thrombolysis. The medications have enzymes in them that interfere with the fibers that form clots, eventually breaking them down and clearing the artery. If it is more severe, a procedure known as angioplasty is performed. Angioplasty, referred to as percutaneous coronary intervention when done on the heart, is a surgical procedure that widens the blood vessels by inserting a catheter and balloon into them. The balloon is expanded to widen the vessel and break-up the deposits that cause blockage.

NSTEMI is treated with medications to keep the arteries open. Percutaneous coronary intervention surgery is sometimes performed, typically when a patient first arrives in the hospital if the blockage is more severe. If there are many blockages and the patient is stable enough, coronary artery bypass surgery may be performed. This procedure can be done for both STEMI and NSTEMI.

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