Download Additional Notes on The Heart

Additional Notes on The Heart
What is a heart attack?
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A heart attack, or myocardial infarction, occurs when one of more regions
of the heart muscle experience a severe or prolonged decrease in oxygen
supply caused by a blocked blood flow to the heart muscle.
Death of the heart muscle often causes chest pain and electrical instability of
the heart muscle tissue.
Electrical instability of the heart causes ventricular fibrillation (chaotic
electrical disturbance). Orderly transmission of electrical signals in the heart is
important for the regular beating (pumping) of the heart.
A heart undergoing ventricular fibrillation simply quivers, and cannot pump or
deliver oxygenated blood to the brain.
Permanent brain damage and death can occur unless oxygenated blood flow is
restored within five minutes.
Many of the heart attack deaths are due to ventricular fibrillation of the heart that
occurs before the victim can reach any medical assistance or the emergency room.
These electrical disturbances of the heart can often be successfully treated with
medications or other means by paramedics in the “field,” or upon arrival to the
hospital. 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.
What causes a heart attack?
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A heart attack is caused by the formation of a blood clot on a cholesterol
plaque located on the inner wall of an artery to the heart (coronary artery).
Cholesterol is a fatty chemical which is part of the outer lining of cells in the
body. Cholesterol plaque is the formation of a hard, thick substance within the
artery walls which is caused by deposits of cholesterol in the artery walls; a
process that begins in the late teens.
Over time, the accumulation of cholesterol plaque causes thickening of the
artery walls and narrowing of the arteries; a process called atherosclerosis.
Plaque accumulation can be accelerated by smoking, high blood pressure,
elevated cholesterol, and diabetes.
Ultimately, atherosclerosis causes significant narrowing of the coronary
arteries. During exercise or excitement, the narrowed coronary arteries cannot
increase the blood supply to meet the increased oxygen demand of the heart
muscle. When the heart muscle is thus deprived of blood oxygen, a condition
called ischemia results; ischemia may be associated with chest pain (angina
pectoris).
Typically, angina occurs with exertion, and subsides with rest. When the
narrowing in the artery becomes critical, angina at rest or “unstable” angina
may result. Unstable angina can be the harbinger of a heart attack in the near
future.
Occasionally the surface of the cholesterol plaque in the artery may rupture, which
leads to the formation of blood clot on the surface of the plaque, which then
completely occludes blood flow in the vessel and results in a heart attack. The cause
of this “plaque rupture” is largely unknown, but contributing factors may include
cigarette smoking, elevated LDL cholesterol, elevated levels of adrenaline, high blood
pressure, and other mechanical and biochemical forces.
What are the symptoms of a heart attack?
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Chest pain or pressure is a common symptom of heart attack. Cardiac chest
pain is often vague, or dull, and may be described as a pressure or band-like
sensation, squeezing, heaviness, or other discomfort.
Heart attacks frequently occur from 4:00 A.M. to 10:00 A.M. due to higher
adrenaline amounts released from the adrenal glands during the morning
hours.
Increased adrenaline in the bloodstream can contribute to the above mentioned
plaque rupture. Interestingly, heart attacks do not usually happen during
exercise, although exercise is commonly associated with exertional angina.
Approximately one quarter of all heart attacks are silent, without chest pain. In
diabetics, the incidence of “silent” heart attacks may be much higher. The pain
or discomfort of a heart attack may be very mild despite its ominous
implications. For this reason, patients may attribute the symptoms to
"indigestion," "fatigue," "stress," or other common maladies.
Denial is also a common element which can dangerously delay the seeking of
medical attention. One cannot overemphasize the importance of seeking
prompt medical attention in the presence of symptoms possibly consistent with
a heart attack
Treatment
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Anti-platelet agents, like aspirin, reduce the tendency of platelets in the blood
to clump and clot. Aspirin is given to ALL patients with a heart attack, unless
there is a history of significant intolerance to aspirin.
An anti-coagulant, heparin, is given intravenously or as a subcutaneous
injection in the hospital as a blood-thinning agent to prevent blood clots and to
maintain an open artery during the initial 24-72 hours.
Nitroglycerin, a vasodilator (blood vessel dilator), which opens the blood
vessel by relaxing the muscular wall of the blood vessel, is given
intravenously to prevent blood vessel spasm and to potentially minimize the
size of the heart attack.
ACE (angiotensin converting enzyme) inhibitors, another class of vasodilators,
are often given orally after a large heart attack to improve the heart muscle
healing process. Examples of ACE inhibitors include captopril (Capoten),
enalapril (Vasotec), lisinopril (Zestril and Prinivil). These medications reduce
the stress load to the heart, thereby helping the damaged heart muscle to
recover.
Beta blocking agents, such as propanolol, metoprolol, and atenolol, are also
often given during the acute heart attack to decrease the amount of muscle
damage.
Long-term administration of these agents following a heart attack has been
shown to improve survival and reduce the risk of future heart attacks.
Oxygen is also commonly administered during the acute phase of a heart attack, as are
narcotics such as morphine; these agents aid in the reduction of discomfort and
actually help minimize the amount of heart damage.
Angina (chest pain) is not a heart attack, but may be a warning of an impending heart
attack. Angina also occurs when the heart muscle is not receiving enough oxygen.
With angina, however, no permanent damage is done to the heart muscle.
Angina is most commonly experienced with an activity such as shoveling snow,
walking upstairs or uphill, consuming a large meal, or a stressful event.
The symptoms of angina are similar to those of a heart attack. They are most
commonly described as a squeezing, burning, tightness, fullness, or pressure across
the chest. This discomfort may radiate to the shoulder, arms (especially the left), neck,
jaw, teeth, earlobes, as well as the upper back between the shoulder blades. Numbness
or tingling in the arms or hands may occur. Angina can be mistaken for indigestion.
Unlike a heart attack, angina may be relieved by rest and/or nitroglycerin within 15
minutes.