1. ACUTE MYOCARDIAL INFARCTION (AMI)

Definition

Acute myocardial infarction is the necrosis (death) of a portion of the heart muscle due to a sudden lack of oxygen, usually caused by an obstruction in a coronary artery.

Epidemiology

• One of the leading causes of death worldwide.

• More common in men over 45 and women over 55.

• Higher incidence in industrialized countries.

Risk Factors

• Hypertension

• Hypercholesterolemia

• Diabetes mellitus

• Smoking

• Obesity

• Physical inactivity

• Family history of heart disease 

Symptoms

• Chest pain (pressing, central or left-sided)

• Pain radiating to the left arm, jaw, or back

• Nausea, sweating, shortness of breath

• Anxiety, feeling of impending doom

• In diabetics and the elderly, it may be silent (without pain)  

Complications

• Arrhythmias (e.g., ventricular fibrillation)

• Heart failure

• Cardiogenic shock

• Rupture of the heart or interventricular septum

• Sudden death 

Pathophysiology – ACUTE MYOCARDIAL INFARCTION (AMI)

What Happens in the Body:

1. Formation of an atherosclerotic plaque

• Fats and cholesterol accumulate in the coronary arteries, forming a plaque.

2. Plaque rupture

• The plaque can suddenly rupture, exposing its contents to the bloodstream.

3. Thrombus (clot) formation

• Platelets activate and form a clot over the ruptured plaque, blocking the artery.

4. Ischemia

• The heart muscle (myocardium) downstream of the blockage doesn’t receive oxygen.

• If the blockage lasts too long (20–30 minutes), cells begin to die.

5. Infarction

• The affected area undergoes necrosis, i.e., cell death: this is the infarction.

• The longer the duration, the greater the damage.

6. Body’s response

• The body may react with arrhythmias, increased heart rate, chest pain, cold sweat.

• The heart loses strength and may develop heart failure.

Resolution (if intervened in time):

• Medical treatment or angioplasty clears the blocked artery.

• Blood and oxygen flow are restored.

• Early intervention can save still-viable myocardial cells.

• With therapy and rehabilitation, the heart can adapt and partially recover function.

Diagnosis – Patient Explanation

1. Electrocardiogram (ECG)

• Purpose: To assess the heart’s electrical activity.

• Findings: Blockages in coronary arteries show changes (like ST segment elevation).

• Importance: Quickly identifies a heart attack and determines the need for urgent intervention. 

2. Blood tests (troponin, CK-MB)

• Purpose: The heart releases certain substances into the blood when damaged.

• Findings: Troponin and CK-MB are markers of cardiac injury.

• Importance: Elevated levels indicate heart muscle cell death, confirming a heart attack.

3. Echocardiogram

• Purpose: An ultrasound of the heart.

• Findings: Assesses heart movement, identifies areas not contracting well, effusions, or complications.

• Importance: Helps determine if the heart attack has damaged part of the heart muscle.

4. Coronary angiography

• Purpose: To visualize the heart’s arteries directly.

• Findings: Identifies blocked arteries and the location of blockages.

• Importance: Allows immediate intervention by clearing the artery with a balloon (angioplasty) or placing a stent.

Pharmacological Therapy – Acute Myocardial Infarction (AMI)

1. Aspirin (acetylsalicylic acid)

• Purpose: To prevent the formation of new clots.

• Mechanism: An antiplatelet agent: prevents platelets from sticking together.

• Monitoring: Watch for possible bleeding (gums, urine, stool); avoid in active ulcers. 

2. Nitroglycerin

• Purpose: To reduce chest pain and improve blood flow to the heart.

• Mechanism: Dilates blood vessels (vasodilator), lowers blood pressure and heart workload.

• Monitoring: Monitor for low blood pressure, headaches, dizziness; check BP before each dose.

3. Beta-blockers (e.g., metoprolol)

• Purpose: To slow the heart rate and reduce oxygen consumption.

• Mechanism: Block the effects of adrenaline on the heart.

• Monitoring: Watch for bradycardia (slow heartbeat), low blood pressure, fatigue.

4. ACE inhibitors (e.g., ramipril, enalapril)

• Purpose: To protect the heart and help prevent heart failure.

• Mechanism: Lower blood pressure and improve heart remodeling after a heart attack.

• Monitoring: Monitor for dry cough, dizziness; check blood pressure and potassium levels.

5. Statins (e.g., atorvastatin, simvastatin)

• Purpose: To lower cholesterol and stabilize arterial plaques.

• Mechanism: Inhibit cholesterol production in the liver.

• Monitoring: Watch for muscle pain; periodically check liver function tests.

6. Heparin or other anticoagulants (e.g., enoxaparin)

• Purpose: To prevent new clots during acute phases.

• Mechanism: Thins the blood more effectively than aspirin.

• Monitoring: Monitor for bleeding, bruising; check blood counts and coagulation parameters.

Nursing Care

• Continuous ECG monitoring

• Pain assessment and administration of prescribed medications

• Vital signs monitoring

• Psychological support for the patient and family

• Health education: diet, smoking cessation, physical activity, home therapy

• Preparation and assistance for diagnostic tests or procedures.

Understanding myocardial infarction on echocardiography

Understanding myocardial infarction on electrocardiogram (ECG)