Heart is the wondrous pump that powers the human body. With each
heartbeat, it sends life-giving blood throughout the body. Blood carries oxygen and food
to all the body cells. The rhythmic beating of the heart begins about seven months before
we are born. When the heart stops beating, we die unless a special device circulates and
oxygenates our blood.
The heart is a large, hollow, muscular organ divided into two pumps
that lie side by side. Veins transport blood from throughout the body to the right-sided
pump. That pump sends the blood to the lungs, where it picks up oxygen. The oxygenated
blood then flows to the left side of the heart, which pumps it through arteries to the
rest of the body. Valves control the flow of blood through the heart. The left-sided pump,
which delivers blood throughout the body, is larger and stronger than the right pump.
The nervous system regulates the heart and other parts of the
circulatory system. A division of the nervous system, the autonomic nervous system,
automatically controls the heart rate, increasing or decreasing it, depending on the
body's needs. For example, the heart pumps slowly while a person sleeps, providing
relatively small amounts of oxygen to the body. But the heart rate can be quickly speeded
up and so increase the oxygen output enormously when a person exercises, becomes
frightened, or needs to fight or run.
Disease can strike any part of the heart. Disorders of the heart and
blood vessels are the leading cause of death in the United States and many other
countries. The most common heart disease affects the arteries that supply the heart muscle
itself with blood. Disorders of those arteries usually develop over a person's lifetime.
Deposits of fatty material block the arteries and so reduce the blood supply to the heart.
If the heart muscle receives too little blood, it may work poorly or even die. Damage to
the heart muscle resulting from a shortage of blood is called a heart attack. A mild heart
attack may force a person to lead a less active life. A severe attack may make the heart
unable to supply the body with enough blood even at rest and so cause a person's death.
Disease may also strike other parts of the heart with equally destructive effects.
Some of the most exciting advances in medicine have been in cardiology,
the medical field that deals with diseases of the heart and blood vessels. For thousands
of years, people with heart diseases did not even know they had such a problem. In the
1900's, doctors have learned to diagnose and treat certain heart conditions that once
meant death. Discoveries of new drugs and the great progress in surgery have added years
to the lives of many heart patients. Doctors have transplanted hearts and even developed
machines that can temporarily do the work of the heart.
Today, much research in cardiology focuses on learning about the causes
of heart disease so that it can be prevented. Other research seeks to reduce death and
disability from heart disease through the further development of new medicines and
surgical techniques. For patients who have untreatable disorders, research continues into
improving heart transplantation and producing an effective artificial heart.
Interesting Facts About The Heart
- The Human Heart is fully developed about eight weeks after
conception, when the embryo is only about 1 inch (2.5 centimeters) long. The heart begins
to beat even earlier--four weeks after conception, when it is just a simple tube.
- Ancient Egyptians believed that the heart was the center of the
emotions and the intellect. An illustration from the ancient
Egyptian Book of the Dead shows the god Anubis weighing a dead person's heart against a
feather, the symbol of truth.
- The Body's Entire Supply of Blood, about 5 quarts (4.7 liters), is
pumped through the body every minute. In one day, the heart pumps nearly 2,000 gallons
(7,600 liters) of blood. In a 70-year lifetime, the heart pumps about 51 million gallons
(193 million liters) of blood and beats 2 1/2 billion times.
- Diseases of the Heart and Blood Vessels are the leading cause of death in the
United States. More than twice as many people die from cardiovascular diseases as from all
forms of cancer. More than half of these deaths are caused by heart attacks.
- Heart Muscle differs in several ways from other muscles in the body. For
instance, heart muscle has certain cells that act as "leaders." These cells
contract and relax rhythmically, causing surrounding cells to do the same. Even when the
leader cells are removed from the heart, they continue their rhythmic beat.
- A Tireless, Powerful Muscle, the heart performs enough work in one hour to lift
3,000 pounds (1,400 kilograms)--roughly the weight of a small car--about 1 foot (30
centimeters) off the ground.
Angina Pectoris, is chest pain that occurs when the heart does not
receive enough blood.
Angiography, is a technique used to X-ray
Angioplasty, is a technique used to
clear arteries that have become blocked with fatty deposits.
Arrhythmia, pronounced uh RIHTH mee
uh, is an abnormal heart rhythm.
Arteriosclerosis, is the hardening,
thickening, and loss of elasticity in artery walls.
Atherosclerosis,is the formation of fat
deposits on the inner lining of arteries.
Atrium, is either of the two upper chambers
of the heart.
Cardiology, is the branch of medicine that
deals with the diagnosis and treatment of disorders of the heart.
Coronary Arteries are the vessels
that supply oxygen-rich blood to the heart muscle itself.
Coronary Artery Disease (CAD) is the
narrowing of the arteries that supply blood to the heart, reducing the amount of blood the
heart muscle receives.
Coronary Bypass is a type of surgery used to
rechannel blood flow past blocked coronary arteries.
Diastole, pronounced dy AS tuh lee, is the
period of heart activity when the ventricles relax.
Electrocardiograph (ECG) is an instrument
used to detect heart damage or diagnose heart disorders.
Heart Attack is a sudden and complete
blockage of a coronary artery, stopping blood flow to one section of heart muscle.
Heart Failure occurs when the heart fails to
pump enough blood.
Systole, is the period of heart
activity when the ventricles contract.
Ventricle, is either of the two lower
chambers of the heart.
The structure of the heart
Each person's heart is about the size of the person's fist. A newborn
baby's heart weighs about 2/3 ounce (19 grams). An adult's heart weighs from 9 to 11
ounces (255 to 312 grams). The heart lies near the middle of the chest, between the lungs.
The heart lies closer to the front of the chest than to the back and slightly to the left
Muscular walls. The heart
consists chiefly of muscle. Heart muscle, also called myocardium or cardiac muscle, forms
the walls of the heart as well as the septum, a wall that divides the left and right sides
of the heart. All the muscles contract and relax, thereby pushing blood through the heart.
A membrane called the epicardium covers the outer surface of the heart.
Another membrane, the pericardium, surrounds the epicardium. It completely encloses the
heart and extends above the blood vessels that emerge from the top of the heart. A
slippery fluid between the epicardium and the pericardium enables the heart to contract
Heart muscle differs from the other muscles of the body--skeletal and
smooth muscles. Skeletal muscles, such as those in the arms and legs, have long fibers
with alternate dark and light bands called striations. We can consciously control the
skeletal muscles. Smooth muscles form the walls of the stomach, intestines, and most other
internal organs. The muscles lack striations, and we do not consciously control them. They
work automatically. Heart muscle has striations like skeletal muscle. But it contracts and
relaxes automatically like smooth muscle. In addition, heart muscle cells act as one cell.
When one heart muscle cell contracts or relaxes, the cells around it do the same. For that
reason, the heart beats continuously and rhythmically throughout a person's life.
Chambers. The septum
divides the heart lengthwise, and valves divide it crosswise. Each side of the heart thus
has two chambers, one above the other. A thin membrane called the endocardium lines each
chamber. The top chambers, called the right atrium and left atrium, receive and collect
blood returning to the heart through the veins. After the atria (plural of atrium) have
filled with blood, they contract and squeeze blood into the lower chambers, called the
right ventricle and left ventricle. After the ventricles have filled, they contract and
pump blood out of the heart through the arteries. The ventricles have extremely thick
walls. The ventricles, which must squeeze blood from the heart, are much larger and
stronger than the atria.
Blood vessels. Blood
enters and leaves the heart through several major vessels. Blood from the body flows into
the right atrium through the body's two largest veins. The superior vena cava brings blood
from the head and arms. The inferior vena cava carries blood from the trunk and legs.
Other blood vessels transport blood between the heart and lungs. Pulmonary veins return
blood from the lungs to the left atrium. The pulmonary artery carries blood from the right
ventricle to the lungs. The aorta is the largest artery. It receives oxygenated blood from
the left ventricle and, through numerous branches, distributes it throughout the body. The
pulmonary artery and the aorta are sometimes called the great vessels.
The first arteries that branch from the aorta are the two major
coronary arteries. They bring blood to the heart and so enable it to continue pumping.
These two coronary arteries divide into many branches as they cover the heart. Diseases
that affect the coronary arteries are among the most serious problems cardiologists treat
because the arteries nourish the heart muscle itself.
Valves regulate the flow of blood through the heart. The valves have
flaps that open as blood pours from a chamber. When the flaps close, they prevent blood
from flowing back into the chamber. Two valves separate the atria and the ventricles. They
are called the atrioventricular valves or AV valves. The AV valve between the right atrium
and right ventricle has three flaps and is called the tricuspid valve. The AV valve on the
left side of the heart has two flaps and is called the mitral valve. The heart also has a
valve, called a semilunar valve, between each ventricle and its great vessel--the
pulmonary artery or the aorta. Each semilunar valve has three flaps shaped like half
moons. When the right ventricle contracts, it delivers blood to the pulmonary artery. The
semilunar valve that controls the blood flow to the pulmonary artery is known as the
pulmonic valve. The left ventricle squeezes blood into the aorta. The semilunar valve on
the left side is called the aortic valve.
The work of the heart
Pumping blood to the lungs.
Blood from the body that enters the right side of the heart contains carbon dioxide, a
gaseous waste the cells produce in creating energy. Blood enters the right atrium through
the superior vena cava and inferior vena cava. The atrium fills with blood and then
contracts, squeezing the blood through the tricuspid valve into the right ventricle. After
the ventricle is filled, pressure forces the tricuspid valve to close and the pulmonic
valve, leading to the pulmonary artery, to open. The ventricle contracts, and the blood
gushes through the pulmonary artery and into the lungs. In the lungs, carbon dioxide is
removed from the blood and oxygen is added. The oxygenated blood then flows through the
pulmonary veins to the left side of the heart.
Pumping blood throughout the body.
Oxygenated blood from the lungs enters and fills the left atrium. The atrium then
contracts, which squeezes the blood through the mitral valve into the left ventricle.
After blood fills the ventricle, the mitral valve closes and the aortic valve opens. Blood
pours into the aorta and flows through arteries to the body tissues.
Regulating the heart rate.
Both sides of the heart pump blood at the same time. As the right ventricle contracts and
sends blood to the lungs, the left ventricle contracts and squeezes blood out to the body.
The heart's cycle of activity has two periods, systole and diastole. Systole occurs when
the ventricles contract, and diastole when they relax. One complete contraction and
relaxation of the heart muscle makes up one heartbeat.
The contraction and relaxation of the ventricles also open and close
the heart valves. Closing of the valves produces the "lub dub" sound of the
heartbeat, which doctors can hear with an instrument called a stethoscope. As the
ventricles contract, the mitral and tricuspid valves close, causing the first sound of a
heartbeat. Immediately after the valves close, pressure in the ventricles forces the
aortic and pulmonic valves to open. After the contraction ends, pressure in the ventricle
drops. The aortic and pulmonic valves then close, causing the second heart sound. The
pressure in the atria is then greater than in the ventricles, and so the tricuspid and
mitral valves open and blood begins to fill the ventricles again.
The autonomic nervous system controls the heart rate. Special cells
send electrical impulses (nerve signals) through the heart, causing it to contract and
relax rhythmically. The impulse begins in a small bundle of muscle fibers called the
sinoatrial node, or S-A node. The S-A node is often called the pacemaker of the heart
because it sets the pace of the heartbeat as it sends out rhythmic signals. The S-A node
lies in the right atrium near where the superior vena cava enters the heart. The S-A node
sends impulses along certain pathways, causing the atria to contract when the electrical
signal reaches them. The impulse then arrives at another node, called the atrioventricular
node, or A-V node. The A-V node lies between the atria and ventricles. It delays the nerve
signal briefly, allowing the ventricles enough time to fill with blood. As the impulse
continues, the ventricles contract.
The nerves of the autonomic nervous system control the S-A and A-V
nodes. Stimulation of those nerves can quicken or slow the heartbeat. When the body needs
more blood, as during vigorous exercise, the nervous system stimulates the S-A node, which
increases the rate of its impulses. The impulses keep the heart chambers contracting at a
faster speed, thus pumping more blood.
A person's size largely determines a person's resting heart rate. The
bigger a person is, the slower the heart rate. A newborn baby's heart beats about 120
times per minute. The typical rate for adults is 72 beats per minute. But doctors consider
resting rates from 60 to 100 beats per minute within the normal range. Athletic training
enlarges the heart and slows the heartbeat. Many well-trained athletes have resting rates
from 40 to 60 beats per minute.
Regulating blood pressure.
Blood in the circulatory system, like water in the pipes of a water system, is always
under pressure. Blood pressure refers to the force with which the blood pushes against the
walls of the arteries. That force drives blood from the heart to all parts of the body.
Each person's blood pressure reflects the amount of blood in the body, the strength and
rate of the heart's contractions, and the elasticity of the arteries. Because the heart
pumps in cycles, pressure in the arteries rises and falls during systole and diastole.
Contraction of the heart produces systolic blood pressure, and relaxation produces
diastolic blood pressure.
The heart helps regulate blood pressure by producing a hormone that
aids the kidneys in eliminating salt from the body. Excess salt may contribute to high
blood pressure, a condition doctors call hypertension. Hypertension can injure the heart,
brain, and kidneys. Over many years, it can damage arteries and lead to heart disease.
Coronary artery disease
Disease can strike any part of the heart. However, the term heart
disease usually means coronary artery disease (CAD), the most common form of heart
disease. The condition affects the blood vessels that nourish the heart itself. CAD
narrows the coronary arteries and so reduces the blood supply to the heart.
About 5 per cent of the blood pumped from the heart goes directly to
the coronary arteries. The blood carries the oxygen and dissolved nutrients (foods) the
heart needs to do its work. The heart can store most nutrients. But it cannot store oxygen
and needs a constant supply. Coronary artery disease may affect the heart's ability to
pump by reducing or stopping the oxygen supply.
Some people with CAD suffer severe pain. Others feel no pain and do not
even know they have a heart problem. If the disease worsens, a heart attack may result. A
heart attack damages the heart muscle or may even cause sudden death. Most cases of CAD
can be treated, but the disease should be diagnosed (identified) as soon as possible.
Cardiologists cannot say for certain who will be stricken with coronary artery disease.
However, medical research shows that certain conditions and habits may lead to the
disease. Doctors call those conditions and habits risk factors. Some risk factors fall
beyond a person's control. For example, CAD strikes more men than women and older people
more than younger ones. In addition, the disease may run in a person's family.
Several other risk factors involved in coronary artery disease can be
controlled. The most important risk factor is the amount in the blood of a fatty substance
called cholesterol. The higher a person's cholesterol level is, the more likely coronary
artery disease will strike because the fatty deposits narrow the blood vessels. People can
control the blood cholesterol level by reducing the amount of cholesterol and animal fats
in the diet. See CHOLESTEROL.
Other controllable risk factors that may cause coronary artery disease
include high blood pressure and cigarette smoking. High blood pressure forces the heart to
work harder, which may bring on a heart attack. People can lower their blood pressure by
losing weight, exercising, and eating less salt. Certain medicines also help reduce high
blood pressure. Cigarette smokers are more likely to have CAD than nonsmokers. Heavy
smokers run more than twice the risk of a heart attack than nonsmokers. But smokers who
quit significantly reduce the risk of heart disease. Other risk factors that may
contribute to the development of coronary artery disease include diabetes, extreme
fatness, and stress.
Regular physical examinations often reveal the development of
controllable risk factors. Doctors may then advise patients to quit smoking or to follow a
specific diet to control high blood pressure, the cholesterol level, or weight.
Causes. Nearly all
coronary artery disease results from arteriosclerosis--a hardening, thickening, and loss
of elasticity of the artery walls. In most cases, the inner layer of the artery wall
becomes damaged, causing a form of arteriosclerosis called atherosclerosis. The inner
walls of healthy arteries are smooth, and so blood flows easily. But in atherosclerosis,
deposits of fats and calcium build up on the inner walls, hampering the blood flow through
the artery. The fat and calcium deposits are called plaques.
Plaques can completely block an artery and stop the blood flow. In
addition, they can narrow an artery and so reduce blood flow enough to form a thrombus
(blood clot). Plaques often crack, releasing substances that also can lead to blood clots.
If a blood clot blocks a coronary artery, it causes a heart attack. A blood clot that
occurs in an artery in the brain causes a stroke.
Symptoms and diagnosis.
Coronary atherosclerosis usually takes many years to develop. Doctors have found coronary
artery plaques in young soldiers killed in battle. But symptoms seldom occur until age 50
or later. In some cases, the first symptom is a heart attack or sudden death. However, a
typical early symptom may be pain in the chest from exercising or some other activity that
makes the heart work harder than usual. Doctors call such pain angina pectoris, or simply
angina. The narrowed coronary arteries supply the heart with less oxygen, which may cause
pain when the heart must work harder. After the exercising or other activity is stopped,
the pain usually disappears. However, angina may worsen if left untreated. Patients may
then suffer from frequent attacks, even when resting.
Physicians diagnose coronary artery disease by first listening to their
patients tell of their general physical condition and past illnesses. They note any
history of angina or heart attack and the presence of any risk factors. Physical
examination may reveal other risk factors, such as high blood pressure or heart damage.
Doctors use an instrument called an electrocardiograph to detect heart
damage or disturbances of the heart rhythm. The instrument produces a record called an
electrocardiogram (ECG), which displays the electrical activity of the heart muscle. The
impulses are printed on moving paper that shows the heart's electrical activity as a
series of wavy lines. Major waves represent contraction of the ventricles. Minor waves
represent relaxation of the ventricles and contraction and relaxation of the atria. Most
ECG's are taken with the patient lying down. But many physicians take a patient's ECG
during exercise. Such a stress ECG shows whether a patient's heart--even if the patient
has no chest pain--receives enough oxygen during vigorous exercise.
Doctors also use a method called radionuclide imaging to detect CAD. A
doctor injects a radioactive element into a patient's bloodstream. The doctor can view the
element on a screen as it spreads into the heart muscle. Areas that do not receive blood
appear blank on the image. Doctors generally use radionuclide imaging with a stress ECG.
If the usual diagnostic techniques leave doubt, physicians may perform
cardiac catheterization followed by coronary angiography. They insert a long, flexible
tube called a catheter through a large blood vessel, usually an artery in the area where
the thigh and abdomen meet. They push the catheter up to where the coronary arteries begin
and inject dye. The inside of the arteries can then be viewed and recorded on X-ray film
called an angiogram. The test clearly shows the condition of the coronary arteries.
Coronary angiography presents a small risk of injury or even death. Doctors therefore
perform it only in difficult diagnostic cases.
Treatment. Doctors cannot
cure coronary artery disease. In some cases, they advise patients to change their life
style to help slow the development of CAD. Victims can be treated with drugs or surgery to
help them live a normal life. Doctors evaluate each patient with CAD to determine which
treatment would provide the greatest benefit.
Physicians prescribe various drugs to treat different symptoms of CAD.
Several drugs relieve angina. For example, nitroglycerin tablets placed under the tongue
enlarge the coronary arteries, enabling more blood to flow past the fatty deposits.
Nitroglycerin can stop angina pain within two minutes. Beta-blockers and calcium blockers
may prevent angina. Beta-blockers slow the action of the heart and reduce its contracting
force. The heart's demand for oxygen then decreases, making it easier for the heart to
pump. Calcium blockers work like beta-blockers on the heart and also relax the coronary
arteries. The two drugs also relieve high blood pressure. The drug digitalis strengthens
the action of weak hearts. Many doctors advise coronary artery disease patients to take
one aspirin tablet a day. Aspirin thins the blood and can help prevent blood clots in the
If drugs fail to control coronary artery disease, doctors consider
other techniques to correct the problem. In the easiest technique, coronary angioplasty or
simply angioplasty, doctors insert a catheter with a deflated balloon attached into the
narrowed area of the coronary artery. They then inflate the balloon, which pushes the
blockage aside and enlarges the artery. Angioplasty works in about 85 per cent of patients
at first. But in about a third of those patients, blockage returns within three months.
For some patients, various methods may prolong the benefits of angioplasty. For example,
intense beams of light from devices called lasers burn away new plaque deposits. Or the
placement of tiny metal props in the artery may keep it open.
Should catheter methods fail, most cardiologists suggest coronary
artery bypass graft surgery. In bypass surgery, doctors first remove a short piece of a
blood vessel, usually a vein from the patient's leg or from an artery in the chest. They
attach one end of the vessel to the aorta and the other end to the affected coronary
artery, bypassing the blocked section. Surgeons can stop the heart to perform a bypass by
using a heart-lung machine. The device has an electric pump and a system of membranes that
do the work of the heart and lungs. The machine removes carbon dioxide from the blood and
delivers oxygenated blood to the body tissues. A coronary bypass can ease symptoms of
angina and prolong the lives of patients with more severe CAD. But it does not stop
Almost all heart attacks occur when a blood clot suddenly and
completely blocks a coronary artery. The condition is called a coronary thrombosis, or
simply a coronary. The heart muscle supplied by the blocked artery becomes damaged because
it receives too little oxygen. Unless blood flow returns within minutes, muscle damage
increases. The heart cells begin to die after four to six hours without blood. The damage
can affect the heart's ability to pump and cause the death of the victim. The body reacts
to a heart attack with its own defenses. Substances in the blood can dissolve clots and
permit blood to flow freely again. If the clot is dissolved within four to six hours of
the attack, the heart suffers less damage.
Symptoms. Before having a
heart attack, many people suffer from angina, feel dizzy, have indigestion, or experience
other symptoms. Some people have no warning signs. Most heart attacks cause severe pain.
Victims describe the pain as a dull, crushing ache in the chest, but it may extend into
the neck, jaw, arms, or back. The pain may last from a few minutes to several hours.
A person who has chest pain and suspects it may mean a heart attack
should seek medical help immediately. Some victims may stop breathing, and their heart may
stop beating. A first-aid technique called cardiopulmonary resuscitation (CPR) can
maintain a person's breathing and circulation until medical help arrives and the victim is
taken to a hospital. But cardiopulmonary resuscitation should be performed only by someone
trained in the technique.
Diagnosis and treatment. Soon
after a heart attack victim reaches the hospital, doctors use an ECG to make sure the
patient actually had a heart attack and not chest pain resulting from some other disorder.
Injured heart muscle causes abnormal ECG waves. Doctors also use certain blood tests to
detect a heart attack. But the tests are not useful until six hours after the attack.
If a victim still has pain, doctors may administer a painkilling drug,
such as morphine. They also use drugs to dissolve clots in the blocked artery. If the
drugs fail to dissolve the clots, doctors may perform emergency angioplasty or bypass
After being hospitalized, heart attack patients are monitored for
complications in the intensive care unit. Two major complications are heart failure and
arrhythmia. Heart failure occurs if the heart does not pump enough blood because of
extensive damage to the heart muscle. In most cases, heart failure can be successfully
treated. In arrhythmia, the heart's electrical system produces an abnormal rhythm. One
kind of arrhythmia, ventricular fibrillation, occurs when electrical signals in the
ventricles fire randomly. Ineffective heart rhythm and sudden death may result from
ventricular fibrillation. Arrhythmias can be readily treated under medical care.
The death rate among heart attack victims who do not get medical care
is more than 20 percent. Some of them die before reaching a doctor. Other victims ignore
their symptoms. The death rate among hospitalized patients ranges from 5 to 10 percent.
Heart attack patients with repeated chest pain, arrhythmias, or heart failure have a
greater risk of another attack than do patients without those problems.
History of heart research
Early beliefs about the heart. In ancient times, many people believed
that the heart had special importance. For example, the Chinese thought that each emotion
originated in a certain organ and that happiness dwelt in the heart. Chinese physicians
diagnosed many illnesses and prescribed treatment by taking the pulse at the wrist. The
ancient Egyptians considered the heart to be the source of intelligence and emotion.
The ancient Greeks learned from battlefield injuries and animal
sacrifices that the heart was a beating organ. In the A.D. 100's, the Greek physician
Galen developed the first medical theories based on scientific experiments. Galen observed
the heartbeat and realized that the heart put blood in motion. But he thought that the
heart's right ventricle forced blood into the left ventricle through holes in the septum.
Galen also believed that the liver converted food into blood, which then flowed through
the body and was used up.
Discovery of circulation.
Doctors accepted Galen's theories--in spite of the many errors--until the 1500's. In the
mid-1500's, a Flemish-born physician named Andreas Vesalius described veins and arteries.
He also showed that no holes exist between the heart's chambers. Also in the 1500's,
Michael Servetus, a Spanish physician and theologian, reasoned that blood flows between
the heart and lungs. But his studies were not publicized because of his unpopular
The theory of blood circulation was first published in 1628, by William
Harvey, an English physician. His work became the basis of modern research on the heart
and blood vessels. Harvey showed that the heart works like a pump. He described how blood
flows from the heart to the lungs, back to the heart, out to the body, and back to the
heart. Harvey believed that small blood vessels called capillaries connect arteries and
veins. The idea of capillaries had been proposed in the 1500's by an Italian anatomist
named Andrea Cesalpino. Marcello Malpighi, an Italian physician, proved their existence in
1661. In the early 1700's, Stephen Hales, an English clergyman and scientist, became the
first person to measure blood pressure. He placed a glass tube in a horse's artery after
breaking through the animal's skin. Hales published the result of this experiment in 1733.
Invention of new medical instruments.
During the 1800's, many inventions expanded doctors' knowledge of the heart and helped in
their diagnosis and treatment of heart problems. In 1816, a French physician named Rene
Laennec invented the stethoscope, which enabled doctors to listen to sounds of the heart
and other organs. In 1880, Samuel Siegfried von Basch, a Viennese physician, developed the
sphygmomanometer, an instrument to measure blood pressure without breaking the skin.
Russian physician Nikolai Korotkoff used a stethoscope in 1905 to take the pulse while
measuring blood pressure, thus recording systolic and diastolic blood pressure. Doctors
still use this technique.
In 1903, Willem Einthoven, a Dutch physiologist, invented the string
galvanometer, a device to measure minute electrical currents generated by the activity of
the heart, and so developed the basis of the electrocardiograph. By the 1920's, the
electrocardiograph had become the chief diagnostic tool in cardiology.
Development of heart surgery.
An American cardiologist named James B. Herrick made the first diagnosis of a heart attack
in 1912. In 1938, Robert E. Gross, an American surgeon, performed the first successful
repair of a congenital heart defect. Gross sewed the hole in the artery of a child
suffering from patent ductus arteriosus. In 1944, Helen Brooke Taussig and Alfred Blalock,
two American physicians, developed an operation to help correct abnormal circulation of
In 1952, American surgeon Charles Hufnagel operated on a beating heart
and implanted the first artificial heart valve. In 1953, another American surgeon, John H.
Gibbon, and his associates successfully used a heart-lung machine they developed, which
enabled doctors to stop the heart while the device pumped and oxygenated the blood.
Doctors could then repair defects that could not be corrected while the heart beat.
F. Mason Sones, Jr., an American surgeon, performed the first
angiography in 1958 and gained the first view of blockages caused by CAD. The coronary
bypass operation was perfected in the late 1960's by Rene Favaloro, an Argentine physician
working in the United States. In 1967, American surgeons Michael DeBakey and Adrian
Kantrowitz successfully implanted the first assisting heart. This device temporarily
helped a diseased or overworked left ventricle.
The first heart transplants and artificial hearts. A team of South
African surgeons headed by Christiaan Barnard performed the first human heart transplant
in 1967. The patient lived 18 days and died of a lung infection. Norman Shumway pioneered
in heart transplants in the United States. He and his surgical team performed the first
U.S. heart transplant on an adult patient in 1968. Shumway refined transplant techniques
and performed more transplants than any other surgeon.
In the late 1960's and early 1970's, doctors performed many heart
transplants. But most patients died within a year, mainly because the body rejected the
new organ. Doctors almost stopped doing heart transplants. Then in the 1980's, they began
using a drug called cyclosporine to fight rejection. Cyclosporine greatly increased the
survival rate among transplant patients. The shortage of donor hearts has become the chief
obstacle to successful heart transplants today.
In 1982, an American surgical team headed by William DeVries implanted
the first permanent artificial heart in a human patient. Robert Jarvik, an American
physician, designed the device. The patient, Barney Clark, suffered from many medical
complications and died 112 days later. A number of other patients received the Jarvik
heart, but none of them survived two years. In 1990, the U.S. Food and Drug Administration
withdrew approval of the Jarvik device. Another model, similar to the Jarvik, is used as a
temporary replacement heart at a few medical centers in the United States.
Progress in treatment and prevention occurred about the same time as
the dramatic advances in heart surgery. In the late 1960's, researchers developed
beta-blockers. These drugs help in reducing high blood pressure, preventing angina, and
controlling certain arrhythmias. Calcium blockers, which work like beta-blockers, appeared
in the 1970's.
In 1977, a Swiss physician named Andreas Gruentzig performed the first
angioplasty, a nonsurgical procedure to open a blocked artery. Researchers also developed
various techniques to use with angioplasty to prolong its effectiveness. The first
implantable defibrillator became available in 1985. The device senses excessive
contractions of the ventricles and sends a small electrical shock to stop them.
Meanwhile, prevention of heart disease has centered on eliminating
controllable risk factors. High blood pressure, high blood cholesterol, and cigarette
smoking are major causes of CAD. Removal of those risk factors may prevent the development
of the disease.
Much of what has been learned about preventing heart disease comes from
extensive medical research. For example, the Framingham Heart Study has provided
considerable knowledge about the risk factors involved in coronary artery disease. The
study began in 1948 in Framingham, Mass., and has examined the functioning of the heart in
more than 5,000 people. Such research has led scientists to develop new drugs to treat
high blood pressure and high cholesterol.
Many people have improved the condition of their heart by learning the
value of preventive medicine. For example, they have their blood pressure and cholesterol
level checked regularly. Many people with mild high blood pressure have reduced it by
limiting the salt and calorie content of their diet. Others have lowered their cholesterol
level by watching the amount of cholesterol, saturated fat, and calories in their diet. In
addition, more and more people exercise regularly, which helps keep body weight down and
so helps lower cholesterol and blood pressure.