Myocardial Infarction

Myocardial Infarction

Myocardial infarction refers to the necrosis in heart muscle resulting from an insufficient supply of oxygenated blood to an area of the heart. The inadequate blood supply is due to SUDDEN occlusion of a coronary artery supplying heart muscles.

Causes of Myocardial Infarction

The following condition can cause myocardial infarction:

  • Atherosclerosis: It refers to the development of fatty deposits on the walls of the arteries in the heart. The deposition of fat makes the arteries narrower and reduces the blood flow to the heart muscles. If place rupture suddenly, a clot forms over it and cause sudden blockage of that coronary artery resulting in heart attack.

Myocardial infarction can also occur due to reasons other than blockage of arteries. The following are such causes, and it constitutes only 5% of all myocardial infarctions.

  • Spasm of the artery: The muscle lining the blood vessels undergo spasm and restrict the blood flow to the heart muscles.
  • Trauma: The injuries to coronary arteries can end up in myocardial infarction
  • Embolism: It is the lodging of a blockage-causing piece of material inside a blood vessel resulting in infarction.
  • Electrolyte imbalance: The high or low levels of important minerals like potassium can cause an infarction.
  • Rare medical conditions: Rare diseases cause narrowing of blood vessels.

Signs and Symptoms of Myocardial Infarction

Signs and symptoms of myocardial infarction include:

  • Chest Pain (Angina) chest pain or discomfort, which is very severe, like crushing, constricting, or weight over the chest. Pain is retrosternal, diffuse, and radiating to the left body side (upper limb and shoulder), right upper limb, jaw, back, and epigastrium.
  • Shortness of breath or trouble breathing
  • Heart Palpitations
  • Stomach discomfort that feels like indigestion
  • Profuse Sweating
  • Drowsiness
  • Fatigue
  • Anxiety or a feeling of “impending doom”
  • Nausea and vomiting
  • Insomnia

Risk Factors of Myocardial Infarction

  • Age: About 80% of heart disease deaths occur in people aged 65 or older. Although now more patients in younger age also having with heart attack.
  • Sex: Males are more likely to develop heart attacks earlier in life than women. The rate of heart attack increases after menopause in women.
  • Family history: It is an independent risk factor for acute myocardial infarction. A family history of acute myocardial infarction in a first-degree relative doubles the risk of myocardial infarction.
  • Lifestyle: Lack of physical activity, a diet high in sodium, sugar and fat, and addictions (smoking, alcohol consumption and drug abuse) increase the risk of heart attack.
  • Comorbidities: Diseases like diabetes, hypertension, hyperlipidemia, and obesity, sedentary increase the risk of myocardial infarction.

Stages of Myocardial Infarction

The myocardial infarction has two phases:

  • An Early Evolving Phase: It comprises the first 6 hours associated with an occluded coronary artery. This phase is usually responsive to treatment.
  • Later Convalescent Phase: After the first 6 hours, the heart attack is not usually responsive to treatment in a way that dead heart muscle may not salvageable by restoring blood supply.

Diagnosis and Tests

The doctors diagnose myocardial infarction by enquiring about the patient’s medical history, signs, symptoms, and physical examination. They may ask the patient to undergo some imaging tests and blood tests.

Various diagnostic tests include:

  • Electrocardiogram (ECG): An ECG is the most basic test for this condition, and it records the electrical signals travelling through the heart.
  • Blood tests: Certain heart enzymes (Troponin–T, Troponin-I, CK-MB, AST, LDH) slowly leak into the blood after heart damage. Blood tests help analyse these enzymes.

In addition, various confirmatory tests could be recommended, such as:

  • Chest X-Ray: It will show the size of the heart, and checks the fluid in the lungs.
  • Echocardiogram: This test is handy to understand heart chambers’ functioning and identify regional wall motion abnormalities.
  • Angiogram (Coronary Catheterization): It is a special type of X-Ray used to visualise the heart’s blood vessels after injecting a liquid dye into it. It shows blocked coronary artery.
  • Cardiac CT scan (Computerised Tomography) or MRI (Magnetic Resonance Imaging): These are the imaging techniques used to create an image of the heart and to assess the extent of heart damage.
  • Biochemical Parameters: Healthcare professionals must assess the patient’s lipid profile, blood sugar, renal parameters, and liver functions.

Alternate Name

Myocardial infarction is commonly known as heart attack.


Acute myocardial infarction is the leading cause of morbidity and mortality worldwide. MI accounts for 10-25% of all deaths in industrialised countries.

Myocardial ischemia with nonobstructive coronary arteries is common in young patients, constituting 9%-15% of all acute myocardial infarction cases.

Expected Prognosis with timely treatment, the damage to heart is aborted with good results.

Poor prognostic factors include:

  • Advanced age
  • Gender (females are more prone)
  • Diabetes
  • Previous heart attack.
  • Late presentation

Long term prognosis depends on ventricular function and degree of obstruction.

Natural Progression

The gross and microscopic changes in the heart show the initial ischemia followed by necrosis or cell death. It eventually leads to tissue fibrosis.


The pathogenesis includes:

  • Occlusive intracoronary thrombus: A thrombus over a plaque results in myocardial infarctions.
  • Vasospasm: The spasm of blood vessels can be with or without atherosclerosis. One can associate it with platelet aggregation.
  • Emboli: It creates blockage inside a blood vessel resulting in infarction.

Possible Complication

80-90% of people develop major complications. 50% of Sudden cardiac deaths occur within an hour.

The few common possible complications are:

  • Arrhythmias
  • Cardiogenic shock
  • Progressive heart failure
  • Thrombus or thromboembolism
  • Myocardial rupture

Primary Prevention

Lifestyle Modification

  • Maintain a healthy weight. Experts consider a BMI of 25 or higher as overweight.
  • Eat a healthy diet, including vegetables, fruits, whole grains, and pulses. Reduce food having excess salt, sugar, and saturated fat.
  • Complete stoppage of smoking and tobacco in any form.
  • Indulge in 30 - 60 min of regular physical activity.
  • Follow relaxation techniques and meditation to manage stress.
  • Undergo regular health Screening, including monitoring blood pressure, blood sugar, and cholesterol levels.
  • Ensure quality sleep.

Secondary Prevention

It focuses on the early detection of the disease and reduces the impact of disease on the life of patients.

Medical Interventions

The most common cause is an abnormal amount of lipid in the blood. Medical professionals commonly use statin therapy to treat it.

Hypertension is another common cause; doctors treat it with beta-blockers and others medicines as appropriate along with advice for lifestyle change.

Lifestyle interventions:

  • Weight reduction
  • Dietary sodium restriction
  • Avoid smoking and tobacco
  • Daily physical activity
  • Stress control

Treatment and Care


  • Anti-clotting medications such as Aspirin and other blood-thinning medicines as indicated
  • Nitroglycerine dilates the blood vessels and relieves chest pain.
  • Thrombolytic (Clot-busting) medications are used in the first 12 hours of a heart attack to break the clot and dissolve it.
  • A heart attack can result in the improper beating of the heart. Antiarrhythmic medications can stop or prevent these malfunctioning.

Interventional Surgery

  • Primary Percutaneous coronary intervention (PCI) restores the blood supply to the affected heart muscle.
  • Coronary artery bypass grafting (CABG) takes a blood vessel elsewhere in the body to create a bypass around the blocked artery section. This procedure is often called open-heart surgery or bypass surgery.

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