ST-segment elevation myocardial infarction (STEMI) is the term cardiologists use to describe the classic heart attack. This is one of the types of myocardial infarction in which part of the heart muscle (myocardium) has died due to a violation of the blood supply to this area.
The ST segment refers to the flat area of an electrocardiogram (ECG) , specifically the flat area that connects two different complexes on the graph (QRS complex and T wave). When a person has the most severe type of heart attack, this segment will no longer appear flat but abnormally elevated.
Types and severity
STEMI is one of the three types of acute coronary syndrome (ACS) . ACS occurs when plaque ruptures within a coronary artery, causing a partial or complete blockage of that artery. The obstruction itself occurs when blood clots form around the ruptured area.
When a blockage occurs, the portion of the heart muscle served by this artery rapidly suffers from a lack of oxygen, called ischemia . Chest pain (angina) is usually the first sign of this. If the blockage is large enough, part of the heart muscle will begin to die, leading to a heart attack.
ACS is classified according to the degree of obstruction and the resulting damage to the heart muscle:
- ST-segment elevation myocardial infarction (STEMI) : When a complete blockage of the coronary artery occurs, leading to the death of heart muscle tissue, we call it STEMI, the worst form of ACS .
- Unstable angina : In some cases, clots form, dissolve, and reform over a period of hours or days without causing a permanent blockage. When this happens, a person may experience angina that comes back over and over again, even at rest. This type of ACS is called unstable angina.
- Non-ST-segment elevation myocardial infarction (STEMI) : occurs when an obstruction does not completely stop blood flow. While some cell death occurs, other parts of the muscle will survive. This may be called a "partial heart attack."
Regardless of how an ACS episode is classified, it is still considered a medical emergency because unstable angina and STEMI are usually early signs of a serious heart attack.
STEMI usually produces severe pain or pressure in or around the chest, often radiating to the neck, jaw, shoulder, or arm. Excessive sweating, shortness of breath, and a deep sense of impending doom are also common.
Sometimes the signs can be much less obvious and present with nonspecific or generalized symptoms, such as:
- Pain in the shoulder blades, arm, chest, jaw, left arm, or upper abdomen
- Pain sensation described as a "clenched fist in the chest."
- Discomfort or tightness in the neck or arm.
- Indigestion or heartburn
- Nausea and vomiting
- Sudden fatigue or exhaustion
- Difficulty breathing
- Dizziness or lightheadedness
- Increased or irregular heart rate
- Clammy skin
As a general rule of thumb, anyone at significant risk for a heart attack should pay close attention to any unusual symptoms above the waistline.
In most cases, the diagnosis of STEMI can be made quickly after the person is under medical care. A review of symptoms followed by an evaluation of the ST segment with ECG is usually sufficient to initiate treatment by a physician. A cardiac enzyme test can also help, but this is usually done after the start of acute treatment.
It is important to stabilize the person as quickly as possible. In addition to pain and stress, STEMI can cause sudden death due to ventricular fibrillation (a serious heart rhythm disorder) or acute heart failure (when the heart cannot pump enough blood to supply the body adequately).
Once a heart attack has happened, the muscle itself can be seriously damaged. A common consequence of this is chronic heart failure and an increased risk of dangerous cardiac arrhythmias (irregular heartbeats).
Treatment should begin as soon as STEMI is diagnosed. In addition to taking medications to stabilize the heart muscle (including morphine, beta- blockers , and statins), efforts will be made to immediately open the blocked artery.
This requires speed. If the artery does not open within three hours of the blockage, at least permanent damage can be expected. Generally speaking, most of the damage can be minimized if the artery unblocks within the first six hours after the attack.
Some damage can be prevented for up to 12 hours. After that, the longer it takes to unblock the artery, the more damage will occur.
Once the acute phase of treatment is complete and the clogged artery is reopened, there is still much to do to stabilize the heart and reduce the likelihood of a second heart attack.
This generally includes a prolonged recovery period, which includes an exercise-based rehabilitation program, diet changes, and the use of anticoagulants (blood thinners) and lipid-control medications.