Myocardial Infarction

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Myocardial Infarction

• Daisy Carmona
• Biology 2401

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What is a myocardial infarction?

• A myocardial infarction is commonly known as
  heart attack.
• A heart attack is the death of part of the heart
  muscle due to its sudden loss of blood supply.
• most heart attacks occur when an unstable,
  atherosclerotic plaque lesion, filled with
  cholesterol and fat, suddenly breaks apart, thus
  forming an open wound within the artery wall.
  Blood platelets and clotting proteins rush to the
  wound and form a clot called a thrombus. The
  clot can enlarge in a matter of moments, causing
  obstruction of blood flow to the heart with
  resultant angina (chest pain). If the blood flow
  becomes completely obstructed, a heart attack
  ensues.
• Many people confuse heart attacks with a stroke.
  But, a stroke or brain attack occurs when a blood
  clot blocks a blood vessel or artery, or when a
  blood vessel breaks, interrupting blood flow to
  an area of the brain, and it has nothing to do
  with the heart.

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What are the causes of a heart attack?

• In his book, The McDoughall Program for a Healthy
  Heart , author John McDoughall, MD, outlines the
  following key elements that can lead to a heart
  attack
• The presence of high total cholesterol and LDL
  cholesterol
• The initial injury to the lining of the artery
  wall
• The formation of unstable, cholesterolfilled,
  fatfilled plaques
• The rupture of the plaque
• The formation of a clot over the open plaque
• The clot closing off blood flow to the heart or
  brain (or other major organ), causing a heart
  attack or stroke.
• At a recent conference on the Mind-Body
  Connection (Friends Connection, Mar,00,
  Moorestown, NJ) that it is his observation that
  many heart attacks can be traced back to a very
  stressful life event that occurred about four to
  seven days prior.

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Visual of a heart attack
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Cause and Effect

• A complete blockage of a coronary artery by a
  blood clot.
• A coronary artery is an artery that supplies
  blood (along with essential nutrients) to the
  heart muscle. Death of the heart muscle often
  causes chest pain and electrical instability of
  the heart muscle tissue.
• Permanent brain damage and death can occur unless
  oxygenated blood flow is restored within five
  minutes.

• The loss of blood supply
• Orderly transmission of electrical signals in the
  heart is important for the regular beating
  (pumping) of the heart. Electrical instability of
  the heart causes ventricular fibrillation
  (chaotic electrical disturbance).
• A heart undergoing ventricular fibrillation
  simply quivers, and cannot pump or deliver
  oxygenated blood to the brain.

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Coronary Artery

• Healthy Coronary Artery
• smooth muscle is red, and connective (supporting)
  tissue is black (elastic) or blue (collagen).

• Coronary Artery with stable plaque

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Coronary Artery (cont.)

• Rupture of plaque in the coronary artery

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Tests that prevent heart attacks

• Angioplasty (Percutaneous Transluminal
  Angioplasty)
• PURPOSE-PTCA is a non-surgical procedure that
  relieves narrowing and obstruction of the
  arteries to the muscle of the heart (coronary
  arteries). This allows more blood and oxygen to
  be delivered to the heart muscle.
• PROCEDURE- PTCA is accomplished with a small
  balloon catheter inserted into an artery in the
  groin or arm, and advanced to the narrowing in
  the coronary artery. The balloon is then inflated
  to enlarge the narrowing in the artery. When
  successful, PTCA can relieve chest pain of
  angina, improve the prognosis of patients with
  unstable angina, and minimize or stop a heart
  attack without having the patient undergo open
  heart coronary artery bypass graft (CABG)
  surgery.
• Electrocardiogram (ECG or EKG)-
• PURPOSE- The electrocardiogram (ECG or EKG) is a
  noninvasive test that is used to reflect
  underlying heart conditions by measuring the
  electrical activity of the heart.
• PROCEDURE- By positioning leads (electrical
  sensing devices) on the body in standardized
  locations, information about many heart
  conditions can be learned by looking for
  characteristic patterns on the ECG.

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Balloon Angioplasty
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Test (cont.)

• Implantable Cardiac Defibrillators
• PURPOSE-The ICD is capable of monitoring the
  heart rhythm. When the heart is beating normally,
  the device remains inactive. If the heart
  develops a life-threatening tachycardia, the ICD
  delivers an electrical "shock(s)" to the heart to
  terminate the abnormal rhythm and return the
  heart rhythm to normal.
• PROCEDURE- A local anesthetic is injected under
  the skin over the area where the ICD will be
  placed, usually in the right or left upper chest
  near the collarbone. The lead is then inserted
  into a vein located in the upper chest near the
  collarbone. The tip of the lead is placed on the
  inner wall of the heart with the visual guidance
  of x-rays. If there is more than one lead, the
  process is repeated. The other end of the lead
  (or leads) is connected to the defibrillator
  unit, which is then inserted under the skin at
  the incision site. Because there are no nerve
  endings inside the blood vessels and the heart,
  the patient usually does not feel the placement
  of the lead(s).

• Homocysteine -
• PURPOSE-testing for homocysteine blood levels is
  conducted because elevated levels of homocysteine
  in the blood are believed to cause narrowing and
  hardening of the arteries. This narrowing leads
  to diminished blood flow through the affected
  arteries. Elevated levels of homocysteine in the
  blood also increase the tendency to excessive
  blood clotting. Blood clots inside the arteries
  further diminish the flow of blood. The resultant
  lack of blood supply to the heart muscles causes
  heart attacks, and the lack of blood supply to
  the brain causes strokes.
• PROCEDURE- Blood testing

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Tests (cont.)

• Coronary Artery Bypass Graft-
• PURPOSE- CABG surgery creates new routes around
  narrowed and blocked arteries, allowing
  sufficient blood flow to deliver oxygen and
  nutrients to the heart muscles.
• PROCEDURE- The cardiac surgeon makes an incision
  down the middle of the chest and then saws
  through the breastbone (sternum). This procedure
  is called a median (middle) sternotomy (cutting
  of the sternum). The heart is cooled with iced
  salt water, while a preservative solution is
  injected into the heart arteries. This process
  minimizes damage caused by reduced blood flow
  during surgery and is called "cardioplegia."
  Before bypass surgery can take place, a
  cardiopulmonary bypass must be established.
  Plastic tubes are placed in the right atrium to
  channel venous blood out of the body for passage
  through a plastic sheeting (membrane oxygenator)
  in the heart lung machine. The oxygenated blood
  is then returned to the body. The main aorta is
  clamped off (cross clamped) during CABG surgery
  to maintain a bloodless field and to allow
  bypasses to be connected to the aorta. The most
  commonly used bypass vessel is the saphenous vein
  from the leg. Bypass grafting involves sewing the
  graft vessels to the coronary arteries beyond the
  narrowing or blockage. The other end of this vein
  is attached to the aorta.

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Coronary Artery Bypass
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Tests (cont.)

• Tilt -table Test
• PURPOSE- The tilt-table test is designed to
  detect one of the most common causes of fainting,
  postural hypotension (orthostatic hypotension).
  Postural hypotension is a common cause of an
  episode of temporary loss of consciousness.
  Postural hypotension results from changing body
  position from a prone, supine or sitting position
  to a more vertical position. Poor tone of the
  nerves to blood vessels in the legs can cause a
  disproportionate distribution of blood to the
  legs, instead of to the brain, so a person feels
  lightheaded and may even faint.
• PROCEDURE- It involves placing a patient on a
  table with a foot-support. The table is then
  tilted upward. The tilt-table may start off in a
  horizontal position and be tilted by degrees to a
  vertical position. The patient's blood pressure
  and pulse and symptoms are recorded with the
  patient in each position.

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Treatment Options

• The immediate goal of treatment is to quickly
  open the blocked artery and restore blood flow to
  the heart muscle a process called "reperfusion."
  Once the artery is open, the heart attack is
  generally halted and the patient becomes pain
  free. Early reperfusion minimizes the extent of
  heart muscle damage and preserves the pumping
  function of the heart. Delay in establishing
  reperfusion can result in irreversible death to
  the heart muscle cells and reduced pumping force
  of the remaining heart muscle. The amount and
  health of the remaining heart muscle is the major
  determinant of the future quality of life and
  longevity for a patient after a heart attack.
  Optimal benefit is obtained if reperfusion can be
  established in the first 4- 6 hours of a heart
  attack.
• Certain clot dissolving medicines (thrombolytic
  agents) such as tissue plasminogen activator
  (TPA) or TNK given intravenously can successfully
  open up to 80 of acutely occluded coronary
  arteries. The earlier these agents are
  administered, the better the success at opening
  the artery, and the more effective the
  preservation of heart muscle. If thrombolytic
  administration is given too late (more than 6
  hours after the onset of the heart attack), most
  of the muscle damage may have already occurred.
  When there will be a potential delay in the
  ability to perform PTCA, either if the hospital
  does not have a catheterization laboratory with
  the ability to perform PTCA, or if there are
  logistic reasons why PTCA will be delayed,
  thrombolytic therapy is then be promptly
  administered to allow prompt reperfusion. PTCA
  may then be performed in patients who fail to
  respond to thrombolytic therapy. Thrombolytic
  therapy carries a significant bleeding risk, such
  that some patients are not candidates for this
  therapy (patients with recent surgery or major
  trauma, recent stroke, bleeding ulcer, or other
  related conditions.

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Symptoms

• A Heart Attack may cause some or all of these
  symptoms
• Pain, pressure, fullness, discomfort or squeezing
  in the center of the chest
• Stabbing chest pain
• Radiating pain to shoulder(s), neck, back, arm(s)
  or jaw
• Shortness of breath or difficulty breathing
• Pounding heartbeats (palpitations) or feeling
  extra heartbeats
• Upper abdominal pain
• Nausea, vomiting or severe indigestion
• Sweating for no apparent reason
• Dizziness with weakness
• Sudden extreme fatigue
• Panic with feeling of impending doom
• Most people report flu-like symptoms.

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Statistics

• Approximately one million Americans suffer a
  heart attack annually. Four hundred thousand of
  these victims die as a result.
• Approximately 90 to 95 of heart attack victims
  who reach the hospital survive.
• The 5 to 10 who later die are those who have
  suffered major heart muscle damage, or who suffer
  an "extension" or enlargement of their heart
  attack.
• Heart attacks frequently occur from 400 A.M. to
  1000 A.M. due to higher adrenaline amounts
  released from the adrenal glands during the
  morning hours.
• 1.5 million heart attacks occur in the United
  States each year with 500,000 deaths.
• A heart attack occurs about every 20 seconds with
  a heart attack death about every minute.
• The National Registry of Myocardial Infarctions
  (New England Journal Med., 22Jul99) reports that
  women have a worse outcome than men after having
  a heart attack. Data showed that women under the
  age of 50 had twice the mortality of men after
  having a heart attack. Variances likely reflect
  increased severity of the disease in younger
  women.

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Statistics (cont.)

• Almost 14 million Americans have a history of
  heart attack or angina.
• About 50 of deaths occur within one hour of the
  heart attack outside a hospital.
• There is a 6 to 9 early mortality from heart
  attack for those who survive long enough to reach
  the hospital.
• From 1983 to 1993, heart attack deaths fell about
  30 overall but have not fallen nearly as much
  for women.
• Studies show the most common time for a heart
  attack to occur is Monday morning. Saturday
  morning ranks second. Another common time is
  during the early morning hours, when blood
  platelets are stickier.
• 60 of women erroneously listed cancer as the
  leading cause of death among women. Deaths from
  all cancers in the USA are half as common as
  deaths from cardiovascular disease.
• Chewing an uncoated aspirin right away, at the
  first sign of chest discomfort or distress, can
  reduce the amount of damage to the heart muscle
  during a heart attack.
• Costs related to heart attack exceed 60 billion
  dollars per year.

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Works Cited

• www.womensheartfoundation.org
• www.medicinenet.com