A myocardial infarction, or heart attack, occurs when a blocked blood vessel deprives the heart muscle of oxygen, leading to tissue damage. A ST-Elevation Myocardial Infarction (STEMI) is a severe type of heart attack defined by an abnormal pattern, ST-segment elevation, on an electrocardiogram. This finding indicates a complete blockage of a major coronary artery.
A STEMI is a time-sensitive medical emergency, as the obstruction of blood flow causes injury through the full thickness of the heart muscle. This event requires immediate medical intervention to restore blood flow and minimize damage.
The Underlying Cause of a STEMI
The heart muscle receives oxygenated blood through coronary arteries. The cause of a STEMI is the complete occlusion of one of these arteries. This blockage is most often the culmination of a long-term process known as atherosclerosis, which involves the gradual buildup of fatty deposits, cholesterol, and other substances into hard structures called plaques within the artery walls.
The event that triggers a STEMI is the rupture of an atherosclerotic plaque. When a plaque tears, the body initiates a clotting process, resulting in a large blood clot (thrombus) at the site. This thrombus can grow large enough to completely obstruct the artery, halting blood flow.
Without a blood supply, the heart muscle is starved of oxygen (ischemia), and if blood flow is not restored quickly, the affected muscle tissue begins to die (infarction). Several risk factors accelerate atherosclerosis:
- Smoking
- High blood pressure (hypertension)
- Elevated cholesterol levels (hyperlipidemia)
- Diabetes
Recognizing the Warning Signs
The most common symptom of a STEMI is chest pain, described as a heavy, squeezing, or crushing sensation in the center of the chest that lasts for more than 15 minutes. The pain may also radiate from the chest to other areas, such as the left arm, jaw, neck, shoulders, or back.
Individuals may also experience other symptoms, including:
- Sudden, profuse sweating (diaphoresis)
- Pale or clammy skin
- Shortness of breath (dyspnea)
- Dizziness or lightheadedness
- Nausea and vomiting
Not everyone experiences these classic symptoms. Women, older adults, and people with diabetes are more likely to have atypical presentations. These can include sudden and overwhelming fatigue, discomfort that feels more like indigestion or heartburn, or a sense of anxiety. Pain may be absent or less pronounced, making it more challenging to identify the event as a heart attack.
Diagnosis in an Emergency Setting
Upon arrival at a medical facility with suspected heart attack symptoms, the primary diagnostic tool is a 12-lead electrocardiogram (ECG or EKG). An ECG should be performed and interpreted within 10 minutes of first medical contact. This test records the electrical signals generated by the heart.
In the context of a STEMI, the ECG reveals a distinct abnormality called ST-segment elevation. The ST segment is a specific part of the heart’s electrical waveform, and its elevation in two or more contiguous leads signals a complete blockage of a major coronary artery.
To confirm the diagnosis and assess heart muscle damage, blood tests measure levels of cardiac biomarkers. The most specific of these is troponin, a protein released into the bloodstream when heart muscle cells die. Elevated troponin levels confirm that a myocardial infarction has occurred, although results may not be immediately available. Therefore, treatment decisions for a STEMI are made based on the ECG findings without waiting for blood test results.
Immediate Medical Interventions
The guiding principle for treating a STEMI is “time is muscle,” as prompt restoration of blood flow saves heart tissue. The preferred treatment is primary percutaneous coronary intervention (PCI), or coronary angioplasty, ideally performed within 90 minutes of arrival at a capable hospital.
During a PCI, a physician guides a catheter through an artery in the wrist or groin to the blocked coronary artery. A balloon at the catheter’s tip is inflated to compress the clot and plaque, and a small mesh tube called a stent is often deployed to keep the artery open.
If a patient cannot be transported to a PCI-capable hospital within 90 to 120 minutes, an alternative strategy is used. This involves administering intravenous “clot-busting” medications known as fibrinolytics, which work by dissolving the thrombus blocking the artery.
Alongside these primary therapies, other medications are administered immediately. A loading dose of aspirin is given to help prevent further blood clot formation, and nitroglycerin may be used to dilate blood vessels and relieve chest pain.
Recovery and Long-Term Management
After immediate treatment, patients are monitored in a cardiac care unit (CCU) to observe heart rhythm and manage complications. The length of the hospital stay varies depending on the extent of heart damage and the patient’s overall condition.
A component of recovery is cardiac rehabilitation, a medically supervised program of exercise, education, and counseling. Its goal is to help patients regain physical strength, improve cardiovascular fitness, and reduce their risk of future cardiac events.
Long-term management involves medications and lifestyle changes. Patients are prescribed drugs to prevent new blood clots, manage cholesterol, and reduce the heart’s workload, including:
- Antiplatelet drugs, such as aspirin and clopidogrel
- Statins to lower cholesterol and stabilize plaques
- Beta-blockers to reduce the heart’s workload
- ACE inhibitors to lower blood pressure
Adopting a heart-healthy lifestyle is a foundation of secondary prevention. This includes:
- Following a diet low in saturated fats and sodium
- Quitting smoking
- Engaging in regular physical activity
- Developing strategies for managing stress