Download Your Heart Anatomy And Procedures

Your Heart
Anatomy and Procedures
Your heart is a muscular organ about the size of your fist. It is located behind the
lower part of your sternum (breast bone). With each beat of the heart, the heart muscle
pumps and circulates blood through the body. The heart can be divided into two sides
with a muscular wall separating them called the septum. Each side of the heart (R & L)
have two chambers stacked on top of each other. The upper chambers are called atria
and the lower chambers are called ventricles.
Blood flow through the heart is a continuous action providing the body with
oxygen rich blood. Every minute, at rest, the heart beats 60-80 beats per minute and
pumps approximately 5 liters of blood through the body. When exercising, the heart rate
and the amount of blood pumped each minute increases to meet the physical demand.
The flow of blood follows a
continuous loop to supply the body
with needed nutrients. The valves
in the heart ensure that the blood
flows in one direction. Oxygen
depleted blood enters the right atria
from the body through the venous
system (vena cava). When the atria
contracts the blood is propelled into
the right ventricle through the
tricuspid valve. When the ventricle
contracts the forward flow of blood
sends the circulation through the
pulmonary valve to the lungs. It is
in the lungs that the blood releases
carbon dioxide and picks up
oxygen. The oxygen rich blood then
returns to the left atria which
contracts and propels the blood
through the mitral valve to the left
ventricle. It is the left ventricle that sends the blood through the aortic valve to the
whole body. Once you understand the blood flow one can see that the ventricles are the
primary pumps of the heart. The left ventricle is the largest muscle chamber in the heart
with the most workload placed upon it.
For the heart muscle to contract it needs a stimulation to direct it. This is done
through an electrical system that is present in the muscle. Each heart muscle cell has
the potential to create stimulation. In a healthy heart, the normal electrical pathways
occur along fixed lines of specialized cells that produce an even contraction when
stimulated.
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Your Heart
Anatomy and Procedures
Electrical stimulation starts in the top of the right atria at the sinus atrial (SA)
node, which has a resting rate of 60-80 firings per minute. This node acts as a spark
plug and fires a stimulation that travels through the atria resulting in contraction of
the right and left atria at the same time.
Because the blood needs to fill the ventricles
from the atria there is a delay in the electrical
charge reaching the ventricles. The electrical
stimulation can only reach the ventricles
through the conducting system, which
consists of the atrioventricular (AV) node
and the bundle of HIS and its branches.
These pathways allow for quick transmission
through the ventricles and a strong contraction
results. The electrical system in the heart is
well balanced and relies on intact pathways.
The system will respond to increased
demands placed on the heart from exercise,
stress or illness by increasing its firing
capabilities. Disruption in the conduction
system will lead to irregular stimulations,
which we call arrhythmias.
Like any muscle in your body the heart also needs to have oxygen to function
and it does this by having its own circulatory system. Coronary arteries are blood
vessels that originate off the aorta and surround your heart muscle. They feed
oxygen rich blood to the heart muscle. There
are two main coronary arteries the left and
the right. The left artery divides into two
arteries the anterior descending branch,
which supplies blood to most of the left side of
the heart and also the septum. The other
branch is called the circumflex and it
provides blood to the outer left and back of the
heart. The right coronary artery supplies
blood to the right side of the heart and in most
people it supplies the blood to the SA and AV
nodes. Over time the heart may produce
additional arteries, which are called collateral
circulation. These vessels increase the
supply of blood through new pathways that
branch off the main arteries. The coronary arteries are susceptible to a buildup of
plaque inside their walls which can lead to blocking the flow of blood to the heart
muscle. This is known as coronary artery disease.
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Your Heart
Anatomy and Procedures
When cardiac disease states exist the function of the heart will be impaired. It is
the goal at COACH to maintain and improve cardiac health through improving risk
factors to optimize the function of the heart.
Cardiac Disease States
Arteriosclerosis
Arteriosclerosis is a chronic disease of the arteries characterized by an
abnormal thickening and hardening of the vessel walls that result in a loss of elasticity.
Atherosclerosis is a specific type of arteriosclerosis, but the terms are sometimes used
interchangeably. Coronary arteries are particularly susceptible to atherosclerosis. In this
condition, thickening of the vessel results in a buildup of plaque made up of fats,
cholesterol, and other substances found in blood. The plaque causes narrowing of the
vessel and can restrict blood flow. This process is known as Coronary Artery Disease
(CAD). It is not usually until the diameter is decreased 70% that symptoms appear in
the form of Angina or chest pain. In the coronary arteries, an unstable plaque deposit
may break off resulting in a rough area on the arterial wall, which may attract the
formation of a clot. It can be this clot formation that creates a 100% blockage of the
coronary artery so that the flow of oxygen rich blood to the heart muscle is blocked
completely. The result of this process is known as a heart attack or myocardial
infarction (MI).
Hypertension (High blood pressure)
Blood pressure is the pressure (mmHg) exerted on the walls of the blood
vessels. The pumping of the ventricle as well as the tension of the artery walls will
determine the blood pressure. The systolic pressure or top number in a blood
pressure result is the measure of the pressure force when your heart contracts and
pushes out the blood from the ventricles. The diastolic pressure or lower number is
the measure of when your heart relaxes between beats.
systolic
120
80
diastolic
High blood pressure or hypertension is an elevation in the blood pressure either
systolic, diastolic or both and is generally felt to be present with consistent pressures
over 140/85. Hypertension increases your risk of cardiac disease, heart attack, and
stroke. Hypertension is one of the most controllable risk factors for coronary artery
disease. It is felt to accelerate coronary artery disease and increase the workload of the
heart. Monitoring and management of high blood pressure is described in Risk Factors
(p.9).
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Your Heart
Anatomy and Procedures
Angina
Angina is the medical term applied to lack of blood flow to the heart muscle
(ischemia) causing pain or discomfort. It occurs when the heart muscle is not getting
enough oxygen. This can result from either a lack of supply of blood through the
coronary arteries to the heart muscle cell and/or an increased demand for oxygen to the
heart muscle cells from exercise, stress or illness. Coronary artery blockages are the
primary cause of angina. The pain or discomfort felt is quite individual and can include
vague sensations, feelings or aches in the chest area. Often people describe angina as
a sense of pressure or burning, squeezing, heaviness, and frequently indigestion. The
pain can radiate to your neck, shoulders or arms. There are primarily two types of
angina. Stable angina is the type that occurs from an increased demand for oxygen. It
usually occurs consistently with a certain level of exertion and is relieved by rest and/or
taking the medication nitroglycerine. Unstable angina is defined as chest
pain/discomfort occurring at rest or if the pattern of angina changes. This is a more
serious form of angina as it may indicate a large blockage in the coronary arteries. It
can be due to coronary artery spasm or plaque rupture (unstable angina). Treatment for
angina is primarily medical through the use of medications and can sometimes include
interventional such as angioplasty, stents, or coronary artery bypass surgery.
Aneurysms
An aneurysm is a ballooning or bulging of a blood vessel due to weakening of the
wall from disease, injury or an abnormality from birth. Often aneurysms occur due to
high blood pressure placed on the weakened area. Aneurysms can occur in vessels in
many vessels including those in and out of heart (aorta), coronary arteries, and the
arteries in the brain. Management includes blood pressure control or surgery to correct
the aneurysm.
Myocardial Infarction or Heart Attack
A myocardial infarction commonly known as a heart attack happens when the
blockage of blood flow (oxygen) to the heart muscle is of sufficient intensity and duration
to cause recognizable death (necrosis) to the heart muscle tissue. It is usually the result
of a blocked coronary artery by a plaque or blood clot. An area of dead muscle
surrounding the blockage cannot be regenerated and instead scar tissue forms in the
area. This scar tissue takes a few weeks to form depending on the size of the infarct
and is non-functioning tissue. That means it cannot contract like the other muscle fiber
nor can it transmit the electrical impulses in the heart. The location & size of the infarct
will determine how the heart functions after. Collateral circulation (newly formed
arteries) may help decrease the amount of damage and may help in the healing
process.
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Your Heart
Anatomy and Procedures
Symptoms include
♥ Persistent, crushing chest pain that may
radiate to arms, jaw, neck, and shoulder
blades (persists > 20 minutes, often
unrelieved by nitroglycerin)
♥ Pressure, tightness, or aching
♥ Nausea, indigestion
♥ Cold Sweat
♥ Shortness of breath
♥ Anxiety, feeling of impending doom
Treatment
♥ Relief of symptoms (morphine,
oxygen, nitroglycerin via intravenous)
♥ Blood thinners to dissolve the clot
and halt heart muscle damage
♥ Risk factor modification to reduce
future heart events
Prompt treatment is necessary as damage occurring to the heart may be minimized if
treatment is started immediately.
Arrhythmias
An arrhythmia is an abnormal rate or rhythm in the heart which results in a
beating of the heart that is not efficient in pumping the blood. These heart rhythms can
be irregular or regular and cause symptoms such as palpitations, dizziness, or fainting.
Treatment can be through medications, surgery, and the use of pacemakers.
Types of arrhythmias include:
Premature contractions are extra beats that can originate either in the atria or
ventricles. Generally these beats are not harmful and do not require treatment if they
are not symptomatic.
Bradycardia is an excessive slowing of the heartbeat. This can originate in the
atria where the sinus (SA) node slows or lower down in the conduction system where
there may be a blockage or slowing of the electrical conduction. Symptoms may
include fatigue, dizziness or fainting. Treatment should be sought and may include
medications or surgical implantation of a pacemaker.
Tachycardia is a rapid beating of the heart. These arrhythmias can originate in
the ventricles or more commonly in the atria. During these rhythms the excessively fast
heart rate is not usually caused by the spark plug (sinus node) but another site or
multiple sites in the atria are firing rapidly. Palpitations, dizziness, and fainting may
occur. Medical attention should be sought and may consist of medications or
cardioversion, which is performed in the hospital.
Atrial Fibrillation occurs where the atria beats irregularly and not as one strong
coordinated contraction. Blood cannot be pumped effectively into the lower chambers.
Atrial fibrillation is the most common tachycardia (excessive fast rate) occurring in ~6%
of individuals over 65 years of age. Treatment is directed to slowing the rate so the
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Your Heart
Anatomy and Procedures
heart can pump more efficiently or eliminating the fibrillation completely by having the
sinus node take over again as the spark plug. This is done through medications or
cardioversion.
Congestive Heart Failure (CHF)
CHF is the inability of the heart to function as an effective pump to meet the
needs of the body. This inability to pump may be a result of a heart attack, viral
infection, intravenous drug abuse or some other illness. Please see Heart Function
section (purple).
Cardiac Procedures
Angiogram:
An angiogram is a test that takes X-ray pictures of the coronary arteries and the vessels
that supply blood to the heart. During the angiogram, a special dye is injected a catheter
into the coronary arteries so that the blood vessels become visible. This allows the
cardiologist to determine if there are any blockages in the coronary arteries.
Angioplasty:
An angioplasty is a procedure designed to dilate (widen or expand) narrowed coronary
arteries, in order to enhance blood flow to the heart. The procedure is very similar to an
angiogram. The catheter used has a balloon on its tip, which is inflated and deflated a
number of times to compress the plaque and enlarge the diameter of the coronary
artery. Frequently a coronary stent is inserted during the procedure to “prop” open the
coronary artery. It is made of a mesh-like material and remains in the coronary artery.
Once properly placed, stents do not move (migrate). This procedure is also known as
Percutaneous Coronary Intervention (PCI).
Transcatheter Aortic Valve Implantation (TAVI):
A TAVI is a minimally invasive procedure that allows doctors to replace a diseased
valve using a long catheter tube inserted through an artery in the groin. A new
specifically designed replacement valve that is attached to a flexible stainless steel
mesh is then sent up the catheter where it is implanted over the existing valve in a
beating heart. This is typically a 90 minute procedure and patients are discharged from
hospital as early as 3-4 days after the procedure. It is offered to patients who are
considered “too sick” for open heart surgery. Aortic valve replacement is still considered
the “gold standard”, with excellent outcomes that have been proven over long periods of
follow-up.
Coronary-Artery Bypass-Graft (CABG) Surgery:
The need for CABG is determined from diagnostic tests and assessment. If the results
of an angiogram show one or more vessels are significantly occluded bypass may be
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Your Heart
Anatomy and Procedures
recommended. CABG or open-heart surgery is a surgical procedure where arteries or
veins are taken from one part of the body and sutured around the blockage in the
coronary artery. A portion of a vein from the leg or arm or the internal mammary artery
is used. During surgery these arteries or veins are connected directly to the coronary
arteries on the surface of the heart beyond the blockages. This way blood can flow
through them to bypass the narrowed or closed points. CABG will improve the blood
flow to the heart. Exercise tolerance is improved and fatigue is reduced. Angina is often
eliminated following CABG.
Echocardiogram: This is an ultrasound of the heart. This enables the doctor to visualize
the hearts function as a muscle, the chambers, and the valves in the heart in a
noninvasive manner aiding in the diagnosis of a variety of cardiac abnormalities.
Electrocardiogram (ECG): This is a graphic record of the hearts electrical system. This
provides important information about the rhythm, size and electrical abnormalities of the
heart, such as previous heart attacks.
Heart Valve Surgery: Heart valves may need repair due to birth defects, rheumatic
fever, bacterial infections or aging. If a valve does not close properly, blood can leak
back through the valve. Heart valve problems increase the workload of the heart. When
the heart can no longer keep up, heart failure may result. Valves can be repaired or
replaced through open heart surgery. The best solution is chosen for each individual
patient based on diagnostic tests.
Pacemaker: This is a small battery operated device that produces the electrical impulse
needed to keep the heart beating in a regular rhythm. The lead (a wire) is implanted in
the wall of the heart. The pacemaker functions like a thermostat, if the pulse drops too
slow the pacemaker will kick in. A pacemaker cannot remove extra beats or prevent
fast rhythms and is used only for bradycardias (slow rhythms). It is usually implanted
under the collarbone or in the abdomen.
Nuclear Medicine Testing: This involves the use of radioactive substances to help
diagnose coronary artery disease and areas of injured heart muscle. These scans are
done at rest and after exercise on the treadmill. The radioactive substance is injected
intravenously and absorbed in the heart. If patients are unable to exercise on a treadmill
(i.e. bad hips), a chemical stress test (Persantine Cardiolite) for the heart is
administered. Persantine is a medication that increases your heart rate mimicking your
heart at exercise.
REFERENCES:
1.
2.
American College of Sports Medicine Resource Manual for Guidelines for Exercise Testing and Prescription. 3 rd ed.
Baltimore: Williams & Wilkins, 1998.
Andreoli K et al. Comprehensive Cardiac Care 6th ed., C. V Mosby Co. 1987.
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Your Heart
Anatomy and Procedures
3.
4.
5.
6.
7.
Canadian Guidelines for Cardiac Rehabilitation and Cardiovascular Disease Prevention. First Edition. National Guidelines
Committee, James A. Stone, BZ, MSc,MD, PhD, FRCPC, Cleo Cyr, Rn CCN, ACSM Certified, et al. 3:39-47, 1999.
The Merck Manual. Sixteenth Edition. 25:473-522, Merck Research Laboratories, 1992.
Micheal D. Lemonick. Where Heart Trouble Begins. Time Magazine July 19, 1999.
American Heart Association. Fighting Heart Disease and Stroke. What is a heart Attack? Angina Pectoris. American Heart
Association (AHA Web site), 2000.
Sibbald, W. Synopsis of Critical Care 3rd ed. Williams and Wilkins., Baltimore. 1988.
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