Myocardial Infarction (MI), commonly known as a heart attack, is a life-threatening condition that occurs when there is a complete blockage of one or more coronary arteries. This prevents oxygen-rich blood from reaching part of the heart muscle, leading to cell death (necrosis).
It is a major cause of morbidity and mortality worldwide and often results from the progression of coronary artery disease (CAD). Early recognition and prompt intervention are critical to saving lives.
Pathophysiology of MI
1. Atherosclerosis:
- Coronary arteries narrow due to plaque buildup (cholesterol, fat, and calcium deposits).
2. Angina:
- Narrowed arteries restrict blood flow, leading to ischemia (low oxygen supply).
- Manifests as chest pain during exertion.
- Plaque rupture triggers the formation of a blood clot (thrombus).
- This completely blocks the coronary artery.
- The heart muscle deprived of oxygen undergoes irreversible necrosis.
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Signs and Symptoms of MI
MI symptoms can vary, but classic features include:
- Sudden, crushing chest pain that radiates to the left arm, jaw, or back.
- Pain that persists despite rest and medications.
- Shortness of breath.
- Nausea and vomiting.
- Sweating (diaphoresis).
- Pale, clammy, or dusty skin.
Atypical Presentation in Women
- Fatigue
- Shoulder blade discomfort
- Shortness of breath
- Sometimes misdiagnosed as indigestion or anxiety
Key Point: Women and elderly patients may present with atypical symptoms, delaying diagnosis.
Diagnosis of Myocardial Infarction
Several diagnostic tools are used to confirm MI:
1. Electrocardiogram (ECG)
- ST-Elevation → Indicates complete blockage (STEMI).
- ST-Depression or T-wave inversion → Suggests partial blockage (NSTEMI).
2. Cardiac Biomarkers
- Troponin: Most sensitive and specific marker of myocardial cell damage.
- Levels rise within hours of infarction.
3. Stress Test
- Used after stabilization to assess residual ischemia.
- Can be chemical or exercise-based.
4. Imaging Studies
- Echocardiogram: Assesses wall motion abnormalities.
- Coronary angiography: Identifies exact site and severity of blockage.
Immediate Treatment: The MONA Protocol
MONA is a mnemonic used for the initial emergency management of MI:
M – Morphine: Relieves pain and reduces cardiac workload.Definitive Treatment
1. Clot-Busting Therapy (Thrombolytics)
- Medications such as Streptokinase, Alteplase (-teplase, -ase drugs) dissolve blood clots.
- Most effective if given within 6 hours of symptom onset.
- Caution: Risk of bleeding must always be monitored.
2. Percutaneous Coronary Intervention (PCI)
- Also known as angioplasty with stent placement.
- Restores blood flow mechanically.
- Preferred over thrombolytics if available.
3. Coronary Artery Bypass Graft (CABG)
- Surgical procedure to reroute blood around blocked arteries.
- Used in multi-vessel disease or when PCI fails.
4. Endarterectomy
- Surgical removal of plaque inside arteries in selected cases.
Prevention and Long-Term Management
After acute management, long-term therapy focuses on preventing recurrence.
Medications
- Antiplatelets (Aspirin, Clopidogrel): Prevent further clot formation.
- Beta-blockers: Reduce myocardial oxygen demand.
- Calcium channel blockers: Improve coronary blood flow.
- Statins: Lower LDL cholesterol and stabilize plaques.
- ACE inhibitors / ARBs: Improve survival post-MI.
Lifestyle Modifications
- Quit smoking.
- Control diabetes and hypertension.
- Adopt a heart-healthy diet (low fat, low sodium, rich in fiber).
- Exercise regularly (under medical supervision).
- Manage stress.
Comparative Table: Angina vs Myocardial Infarction
| Feature | Angina | Myocardial Infarction (MI) |
|---|---|---|
| Cause | Partial blockage of coronary arteries | Complete blockage of coronary artery |
| Pain Duration | Few minutes | >20 minutes, persistent |
| Relief | Rest, nitroglycerin | Not relieved by rest/medications |
| ECG | ST depression (ischemia) | ST elevation (STEMI) or T-wave inversion |
| Troponin | Normal | Elevated |
| Outcome | Reversible | Irreversible myocardial damage |
Conclusion
Myocardial Infarction (MI) is a cardiac emergency caused by complete blockage of coronary arteries. It evolves from atherosclerosis and angina to infarction when a clot forms and obstructs blood supply.
- Classic symptom: Crushing chest pain radiating to the arm or jaw.
- Key diagnosis: ECG + Troponin.
- Initial treatment: MONA protocol.
- Definitive treatment: PCI, CABG, or thrombolytics.
- Long-term care: Antiplatelets, statins, lifestyle modifications.
Prompt recognition and treatment dramatically improve survival rates and reduce complications.
FAQs on Myocardial Infarction
Q1: What is the difference between STEMI and NSTEMI?
STEMI: Complete blockage of coronary artery with ST-elevation on ECG.
NSTEMI: Partial blockage with elevated troponin but no ST-elevation.
Q2: How quickly should treatment for MI begin?
Ideally within the first 90 minutes (“golden hour”) for best outcomes.
Q3: Can women have a heart attack without chest pain?
Yes, women often present with atypical symptoms like fatigue, shortness of breath, or back pain.
Q4: What foods should MI patients avoid?
High-fat, high-salt, and processed foods. Instead, follow a Mediterranean-style diet.
Q5: Can MI be prevented?
Yes. By controlling risk factors—smoking, hypertension, diabetes, cholesterol, obesity—and adopting a heart-healthy lifestyle.
