A COMMON DISEASE IN HK

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A COMMON DISEASE IN HK

• CHAN CHUNG
• 7B

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Acute myocardial infarction (AMI)

• Acute myocardial infarction (a medical term for
  heart attack) is the rapid development of
  myocardial death caused by a critical imbalance
  between the oxygen supply and demand of the
  myocardium.

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• This usually results from plaque rupture with
  thrombus formation in a coronary vessel,
  resulting in an acute reduction of blood supply
  to a portion of the myocardium. It is a
  non-infectious disease

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This is a normal coronary artery with a nice,
big, unobstructed lumen for supplying plenty of
blood to the myocardium.
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This composite picture demonstrates cross
sections of coronary artery with atherosclerosis.
At the left the lumen is about 50 blocked. At
the left, there has been thrombosis with
organization and recanalization to leave three
small remaining lumens.
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This cross section of coronary artery
demonstrates 75 narrowing
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CAUSES

• The most common cause of AMI is narrowing of the
  blood vessels due to atheromatous plaques, which
  contain cholesterol and deposit on the blood
  vessels.

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• The roughness of these areas may promote platelet
  breakdown and sets in motion the clotting
  process. This is development of thrombus. This
  can result in partial or complete occlusion of
  the vessel and cut off the oxygen supply from
  blood. This course accounts to about 90 of this
  disease.

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• The other course is the vasospasm (contraction of
  the muscular coats of the blood vessels) of the
  coronary arteries. This may lead to the slowing
  down of blood flow and even rupture of the inner
  lining of the coronary arteries and bleed. This
  results in thrombosis.

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This is normal myocardium. There are cross
striations and central nuclei.
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This is an early acute myocardial infarction.
There is increasing loss of cross striations, and
some contraction bands are also seen.
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LONG TERM REASONS

• There are several risk factors that are supposed
  to increase the incidence of acute myocardial
  infarction.

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• Smoke-----Carbon monoxide and nicotine in the
  cigarette allow easier penetration of cholesterol
  into blood vessels.
• Nicotine narrows the blood vessels, causing an
  increase in blood pressure and heart rate.
• Carbon monoxide competes with oxygen in the red
  blood cells so that there is less oxygen carried
  to the heart. Smokers produce more fibrinogen
  which greatly stimulates the sticking of blood
  platelets on the surface of the inner lining of
  the artery.

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• Obesity-----Excess weight increases the work of
  the heart to supply the body with the needed
  oxygen. It also raises blood pressure and blood
  cholesterol levels which can speed up the
  atherosclerotic process.

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• High blood pressure-------High blood pressure
  increases the workload of the heart, causing its
  wall to thicken and become stiffer

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• It has also been shown that people with gout
  (caused by high uric acid in the body) has higher
  chance of AMI. This is because the uric acid
  deposited on the coronary artery and speeds up
  the thrombosis

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SYMPTOMS

• Chest pain,
• Pain may radiate to the jaw, neck, arms, back.
  The left arm is affected more frequently than the
  right arm.
• Anxiety
• Cough
• Nausea and vomiting
• Wheezing
• Elderly patients and those with diabetes may feel
  fatigue or weakness.

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• Sudden death is defined as death occurring within
  an hour of onset of symptoms. Such patients tend
  to have severe coronary atherosclerosis (75
  lumenal narrowing). Often, a complication such as
  coronary thrombosis or rupture has occurred. The
  mechanism of death is usually an arrhythmia (Loss
  or abnormality of rhythm, denoting especially an
  irregularity of the heartbeat)

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TREATMENT

• Antithrombotic agents -- These agents prevent the
  formation of thrombus associated with myocardial
  infarction and inhibit platelet function by
  blocking cyclooxygenase and subsequent
  aggregation. Antiplatelet therapy has been shown
  to reduce mortality by reducing the risk of fatal
  myocardial infarctions, fatal strokes, and
  vascular death. Aspirin is one of the example.

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• Beta blockers -- reduce blood pressure, which
  decreases myocardial oxygen demand. These drugs
  also reduce the activity of the sympathetic nerve
  and hence reduce the workload of the heart.

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• Thrombolytic(Breaking up or dissolving a
  thrombus) agents -- These agents dissolve the
  thrombus deposited on the coronary artery to make
  the blood flow again and prevent the death of the
  myocardium. This kind of treatment works most
  efficiently 6 hours after the onset of acute
  myocardial infarction

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PREVENTION

• Having diets with low salt, low cholesterol and
  low fat to prevent obesity and lower blood fats
• Doing regular exercise can improve heart
  function, blood pressure and blood cholesterol
  level

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• Quit smoking

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END
LSC Good picture, good presentation