Introduction
A heart attack (myocardial infarction) is a medical emergency in which blood flow to the heart is cut-off. Heart attacks occur due to constriction and blockage of blood vessels that supply oxygenated blood to the heart. This lack of oxygen supply damages the heart muscles and leads to a heart attack. STEMI (ST-elevation myocardial infarction) is a type of heart attack affecting the heart's lower chambers. The electrical activity in the heart’s lower chambers is altered in STEMI, leading to a more serious and life-threatening type of heart attack. STEMI is usually very severe and fatal. Two to ten percent of patients who have had STEMI die within a month’s time. Thus, prompt emergency medical management plays a crucial role in determining the survival and prognosis of the patient.
What Happens in STEMI?
An acute coronary syndrome is an umbrella term that includes ST-elevation type of heart attack (STEMI), non-ST-elevation heart attacks (NSTEMI), and unstable angina (sudden chest pain at rest). In all three heart problems in acute coronary syndrome, the blood flow to the heart is limited or blocked. In STEMI, the blood flow to the heart is blocked due to clots or fat obstructing the heart's major blood vessels (coronary arteries). The muscles of the heart begin to get damaged and die due to the lack of blood and oxygen. This causes a distinct wave pattern in the electrocardiogram (ECG), a test that measures the heart’s electrical activity. The ST segment of the wave (in the electrocardiogram result wave pattern) is usually flat in normal people.
However, in STEMI, the ST segment of the wave is elevated. This denotes that one of the blood vessels supplying the heart is completely blocked and that the muscles of the heart’s lower chambers (ventricles) are in the process of dying due to the absence of blood flow. The muscles of the heart’s lower chamber (ventricles) pump blood to all body parts, lungs, brain, and other vital organs. If they get damaged and die, the heart will be unable to pump blood to support the body, leading to a life-threatening emergency. If the muscles of the heart’s lower chamber go without blood supply for a longer duration, the damage can be permanent. This can be prevented or minimized with prompt and timely management of the heart attack and restoring blood flow to the heart by removing the blocks in the blood vessels.
What Are the Warning Signs of STEMI?
Not all heart attacks are intense and sudden. They exhibit a wide range of symptoms varying between individuals. If a person exhibits the symptoms of a heart attack, it is important to call for emergency care or rush to the emergency department to ensure survival. The most common warning signs to look for include the following:
-
Chest discomfort that does not go away, pressure or tightness in the chest.
-
Chest pain radiating to the left arm.
-
Intense central chest pain.
-
Radiating pain (to both arms, jaws, back, or stomach).
-
Breathlessness or shortness of breath.
-
Cold sweats.
-
Dizziness or fainting.
-
Increased heart rate.
-
Faint heartbeat.
How Is STEMI Diagnosed?
The healthcare provider performs various tests to confirm STEMI (heart attack). These include:
-
Electrocardiogram (ECG): Electrocardiograms show the electrical activity in the heart in the form of a wave pattern. This test is crucial in diagnosing ST wave segment elevation in STEMI.
-
Echocardiography: This is an imaging test to look for any abnormalities in the heart structure, muscles, and valves.
-
Computed Tomography: This scan generates a detailed image of the heart (layer-by-layer) using X-rays and computerized processing. At times, a dye or contrast is injected into the patient’s blood to check for blockages in the blood vessels.
-
Magnetic Resonance Imaging (MRI): High-resolution images of the heart are obtained using magnetic resonance imaging.
-
Lab Tests: When the heart muscles get damaged, they release troponin (a chemical) into the blood. Thus testing for troponin in the blood helps to confirm a heart attack.
How Is STEMI Managed in the Emergency Department?
Time plays a crucial role in STEMI treatment. The quicker treatment is initiated, the more favorable outcome is expected. If the patient’s blood oxygen levels are low, oxygen supplementation is given. The various treatments for STEMI include:
1. Percutaneous Coronary Intervention: A catheter (or a hollow tube) is inserted into a major blood vessel (of the wrist or thigh) and is threaded up to the heart. Then, a dye or contrast is injected into the blood vessels to identify the block or obstruction. Once the block is identified in the major blood vessels supplying the heart, a balloon is inflated on the end of the catheter to clear the block, ensuring blood flow to the heart. This procedure is performed by highly skilled heart specialists (interventional cardiologists). Sometimes, a stent (a scaffold-like device) is placed during the percutaneous coronary intervention to hold the blood vessel open to prevent another clot from blocking it.
2. Medications: Various medications are administered to stabilize the patient and to treat the heart attack. These include:
- Beta-Blockers: These medications slow down the rate at which the heart beats, enabling the heart muscles to handle the decreased blood supply. These reduce heart damage and prevent irregular rhythms.
- Statins: High blood cholesterol can result in plaque formation (fatty deposits) in the major blood vessels supplying the heart, blocking the heart’s blood supply. Statins are medications that prevent the production of cholesterol in the liver, thus lowering blood cholesterol levels.
- Antiplatelet Medications and Aspirin: The medications are blood thinners that prevent clot formation in the heart’s major blood vessels and stents.
- Clot Dissolving Medications: Medications to dissolve the clots blocking the blood vessels (thrombolysis) are administered in STEMI.
- Nitroglycerin: Nitroglycerin causes the blood vessels to widen (vasodilatation), thus ensuring sufficient blood flow. It relieves chest pain caused due to blood vessel blockage.
- Pain Medications: Strong pain medications such as Morphine are used to treat severe chest pain.
3. Surgery: Coronary artery bypass grafting or open heart surgery is a surgical procedure used in severe or complete blockage of the heart's major blood vessels. A graft (a blood vessel from another body part) is used to bypass the block, and the blood is diverted around the block to reach the heart. This procedure restores the blood and oxygen supply to the heart.
Regular follow-ups and diagnostic check-ups are necessary after an episode of STEMI or heart attack. Cardiac rehabilitation programs that provide advice on diet, nutrition, exercise, and physical training also help recover after a heart attack.
Conclusion:
ST-elevation myocardial infarction (STEMI) is a type of heart attack that is typically severe and fatal. It is a medical emergency that requires prompt medical attention and treatment. One of the major blood vessels (coronary arteries) supplying blood and oxygen to the heart is completely blocked (with clots or plaques) in STEMI. The heart muscles (of the lower chambers) undergo permanent damage and die. This is life-threatening and requires prompt treatment with medications, invasive procedures such as percutaneous coronary intervention, and open heart surgeries to restore blood flow.
