How do artery blockages lead to Heart Attack?

A heart attack occurs when there is a blockage in the artery supplying blood and oxygen to the heart. Sometimes, there is the building of fatty deposits in heart arteries, causing plaque formation over time. A plaque rupture results in blood clot/s, potentially blocking the heart arteries, causing a heart attack.

In myocardial infarction, there is an insufficient supply of oxygen-rich blood flow to the heart muscle resulting in damage to that region. The heart muscle usually begins to die if the blood supply is not restored with treatment.

Types:

• STEMI (ST-segment elevation myocardial infarction) Heart Attacks – ST segment is elevated in ECG as the coronary artery is completely blocked. A large part of the heart muscle does not receive blood.
• NSTEMI (non-ST-segment elevation myocardial infarction) Heart Attacks – No change in the ST segment in ECG. Partial blockage of the coronary artery and less damage to the heart muscle.
• Coronary artery spasm – Blood flow through the artery is restricted as the artery wall tightens, causing a heart attack.
• Demand ischemia – Arteries are not blocked, but the heart’s demand for oxygen is more than that available in the body. 

What are the Causes of Heart Attack?

A heart attack occurs when the blood and oxygen supply to the heart muscle is cut off, resulting in damage to the heart muscle. This damage becomes irreversible if the blood supply is not restored within 30 minutes of blockage. The common causes of heart attack are:

• Blockage of the coronary arteries by cholesterol and other substances.
• Coronary artery disease or Atherosclerosis – Deposition of fat in the artery or plaque that may rupture and cause blood clot resulting in complete or partial blockage of blood flow through the coronary artery.
• Spontaneous coronary artery dissection (SCAD) – Condition in which one or more of the coronary arteries tear.
• Spontaneous coronary artery dissection (SCAD)
• Severe spasm of the coronary artery.

Risk factors:

• Age – Men above 45 years of age and women above 55 years are at a higher risk.
• Family history – People with a family history of heart disease, especially those whose relatives were diagnosed before 55 years of age, show a higher incidence of a heart attack.
• Medical conditions – Type 1 diabetes, high blood pressure, high levels of triglycerides, or LDL cholesterol are more likely to get a heart attack.
• Unhealthy lifestyle habits – Smoking, excessive alcohol consumption, sedentary lifestyle, and a diet rich in saturated fat show a higher heart attack rate.
• Preeclampsia – This condition develops during pregnancy and is characterized by a rise in blood pressure and excess protein in the urine. It increases the lifetime risk of a heart attack in women.
• Metabolic syndrome – is another risk factor for heart attack, like obesity, high blood pressure, and high blood sugar are called. 
• Gender – Men are more susceptible at a younger age as compared to women. The risk factor in women rises after menopause.

Signs and symptoms of Heart Attack

• Pain or discomfort in the center or left side of the chest that lasts for more than a few minutes
• Pain in one or both arms, back, shoulder, neck, jaw, and upper part of the stomach.
• Shortness of breath
• Unusual tiredness for no reason
• Sweating
• Nausea
• Dizziness
• No pain or an indigestion type of discomfort (seen in “silent heart attack”).

Complications:

Complications associated with a heart attack that requires medical care are:

• ArrhythmiaComplete heart block
• Heart failure
• Cardiogenic shock
• Heart rupture

Diagnosis:

• Electrocardiogram (ECG) identifies signs of heart damage and that of previous or current heart attack as it records the heart’s electrical activity.
• Blood tests – Levels of troponin, creatine kinase (CK) or CK–MB tests, serum myoglobin, and other proteins in the blood are evaluated to identify the heart damage and signs of a heart attack.
• Coronary Angiography – Blockages in the coronary artery are determined using special x–rays and a catheter.
• Echocardiogram (echo) – Soundwaves are used to identify which regions of the heart are damaged and their impact on heart functioning.

How is Heart Attack treated?

• Restoring the blood flow to the heart muscle to limit the damage to the heart muscle is the primary goal of early treatment.
• The other main treatment objectives are to relieve pain, preserve the heart muscle function, and prevent death.
• Medical Procedures – 
  • Coronary angioplasty or percutaneous transluminal coronary angioplasty (PTCA) – A balloon is used to open the blood vessels. A stent is kept to keep the artery open. The different types of PTCA are:
    • Balloon angioplasty
    • Coronary artery stent
    • Atherectomy
    • Laser angioplasty
  • Coronary artery bypass grafting – Rerouting the blood to restore the blood supply to the heart muscle by bypassing the blocked section of the coronary artery.  
• Medications – The different drugs used to treat and prevent heart attacks are:
  • Angiotensin-converting enzyme (ACE) inhibitors – Captopril, enalapril, etc. to lower blood pressure and reduce strain on the heart.
  • Anticlotting medicines – Aspirin, clopidogrel, etc., to prevent platelets from clumping and forming unwanted clots.
  • Anticoagulants – Dabigatran, edoxaban, etc., to prevent clot formation in arteries.
  • Beta-blockers – Metoprolol, acebutolol, etc., to decrease the heart’s workload and prevent another heart attack.
  • Statins – Atorvastatin, lovastatin, etc., to lower blood cholesterol levels to reduce the chances of another attack.
• Emergency treatment – 
  • Intravenous therapy – Nitroglycerine to dilate the arteries, relieve the chest pain, and morphine to reduce the myocardial oxygen demand and ease the pain.
  • Oxygen therapy – To improve oxygenation to the damaged heart muscle.
  • Fibrinolytic therapy
  • Antiplatelet therapy
  • Monitor the heart and vital signs continuously.

How to prevent Heart Attack? How to live with it?

• Living with a heart attack –
  • Regular checkup and medical follow up
  • Heart-healthy eating
  • Managing stress
  • Maintaining a healthy weight
  • Quitting smoking
• Preventing a heart attack –
  • Cardiac rehabilitation to prevent another attack 
  • Increase physical activity
  • Improving mental health
  • Taking the prescribed medications

When to see a doctor? :

Contact a cardiologist or the local emergency number immediately if there is severe pressure or pain in the center of the chest that gets worse or doesn’t get better by taking nitroglycerin. The cost of coronary angiography ranges from Rs. 10K to 15 K, and that of bypass surgery lies around Rs. 3 to 4 lakhs.

References:

• [1] – https://www.cdc.gov
• [2] – https://www.heartfoundation.org.nz
• [3] – https://www.hopkinsmedicine.org
• [4] – http://www.secondscount.org
• [5] – https://www.nhlbi.nih.gov
• [6] – https://www.nhs.uk