Ablation
Non-surgical destruction of heart tissue by using a catheter to direct
an electrical current or radio frequency to the tissue. Used, for instance, in the
treatment of Wolff-Parkinson-White syndrome.
Accessory pathway
An extra pathway that bypasses the normal route of electrical
conduction, allowing electrical impulses to travel from the atria to the ventricles
without passing through the AV node and bundle of His. For instance, in
Wolff-Parkinson-White syndrome, an accessory pathway known as bundle of Kent occurs
between the atria and ventricles causing early depolarization of the ventricles. See
Wolff-Parkinson-White syndrome
Acid-base balance
Balance of the level of acids and bases in the blood and plasma. Normal
blood pH is 7.35-7.42. The most common acid is hydrogen ions. The most common base is
bicarbonate.
Acidemia
Abnormally high level of acid in the blood, low pH (< 7.35)
resulting from either the accumulation of acid in the blood or the loss of base from the
body.
Acidosis
Acidosis is a severe condition resulting from either the accumulation
of acid in the blood or the loss of base from the body.
Acute myocardial infarction
Acute myocardial infarction occur following acute myocardial ischemia
with sufficient severity and duration to result in permanent myocardial damage.
Alkalemia
A blood pH above normal (> 7.45) resulting from either the
accumulation of base in the blood or the loss of acids from the body.
Alkalosis
Alkalosis is a condition resulting from either the accumulation of base
or loss of acid from the body.
Aneurysm
An aneurysm is an abnormal dilation or swelling of a blood vessels or
ventricles
Angina pectoris
A clinical syndrome due to myocardial ischemia typically characterized
by a discomfort or pressure that is deep and poorly localized on the chest or arm,
typically associated with physical exertion and relieved promptly by rest.
Angiotensin-converting enzyme (ACE)
An enzyme found in the lungs that converts angiotensin I to angiotensin
II. Angiotensin II is a vasoconstrictor that also acts in the kidneys to cause retention
of water.
Angiotensin converting enzyme (ACE) inhibitor
ACE inhibitors are vasodilator drugs used to decrease pressure by
interfering with the conversion of angiotensin I to angiotensin II, therefore decreasing
peripheral vascular resistance.
Antegrade
Antegrade is flow in the normal direction.
Aorta
The aorta is a large artery arising directly from the left ventricle,
carrying oxygenated blood from the left ventricle to the systemic circulation.
Aortic valve
Are semilunar valve that separate the left ventricle from the aorta.
They open in systole (ventricular contraction) to allow flow of blood out of the aorta and
close at the end of ventricular contraction to prevent backflow of blood into the left
ventricle.
Arrhythmia
An irregular heartbeat or disturbances in heart rhythm.
Arteriole
A small blood vessel branching off of an artery. Arterioles further
divide to give rise to the capillary network.
Arteriosclerosis
Arteriosclerosis is the progressive thickening and loss of elasticity
in the walls of arteries due to deposition of plaques consisting of cholesterol,
platelets and clots.
Artery
A blood vessel that carries blood away from the heart. All arteries
except the pulmonary artery carry oxygenated blood.
Ascending aorta
The ascending aorta is the portion of the aorta which begins at the
aortic valve and extends upward to the aortic arch, connecting the aorta arch to the left
ventricle.
Asystole
Asystole is when the heart does not beat.
Atherosclerosis
The progressive blockage of arteries from a build-up of fatty plaques
on the inner artery walls.
Atria
The atria are the upper chambers of the heart that collect blood
before passing it on to the ventricles (atrium singular). The right atrium is the upper
right cardiac chamber that receives deoxygenated blood from the inferior and superior
venae cavae and delivers blood to the right ventricle. The left atrium is the upper left
cardiac chamber that receives oxygenated blood from the pulmonary veins and delivers blood
to the left ventricle.
Atrial fibrillation
Atrial arrhythmia is characterized rapid atrial rhythm due to multiple
reentrant "wavelets" travelling throughout the atria, causing the upper chambers
to contract in a chaotic manner (fibrillate). There are usually no P waves. Ventricular
rhythm may be normal, although a wider QRS of the ventricular escape rhythm. Atrial
fibrillation may occur in hypertensive diseases or pericarditis.
Atrial flutter
Atrial flutter is a rapid atrial rhythm, usually at about 300 bpm,
characterized by a 'sawtooth' waveform. It occurs due to one or two macroreentrant
circuits within the atria.
Atrial tachycardia
A rapid atrial rhythm (150-200 bpm) in which the QRS complex remains
normal. There my be some overlap of the T and P wave.
Atrioventricular fistula (AV fistula)
An atrioventicular fistula is a abnormal connection between an artery
and a vein, bypassing the capillary bed.
Atrioventricular node (AV node)
Specialized heart conducting tissue that receives impulses from the
sinoatrial node and propagates them to the ventricles. It is located between the atria and
the ventricles in the lower-middle of the right atrium. It serves as an electrical relay
station by briefly slowing the electrical impulses traveling from the atria to the
ventricles to allow time for the atria to contract and fill the ventricles before the
ventricles contract.
Atrioventricular Septum
The physical wall that separates the atria from the ventricles.
Autonomic nervous system
Autonomic nervous system is the part of the nervous system that
controls unconscious systemic functions, such as respiration and beating of the heart. The
autonomic nervous system is divided into two; the sympathetic and the parasympathetic
nervous system. These two systems govern are responsible for opposing signals. A
sympathetic signal ("fight or flight") will speed the heart rate and strength of
contraction. A parasympathetic signal slows the heart rate. In this way, the
autonomic nervous system regulates the blood pressure.
Autoregulation
The ability of an organ system to control the blood flow to itself by
dilating or constricting the arterioles that supply blood to it to meet it's metabolic
needs.
B
Beta blocker
A group of drugs that reduce heart rate by blocking the effect of
catecholamines and the sympathetic nervous system to the heart. A decrease in heart rate
causes a decrease in oxygen demand in the myocardium.
Bicarbonate
The most common and important base found in the plasma and
blood. Bicarbonate is a important metabolic component of the acid-base balance,
involved in regulation on the normal acid-base balance (pH 7.35-7.42). The bicarbonate ion
concentration is regulated by the kidneys by increasing or decreasing the resorption of
HCO3- in the renal tubule. The normal [HCO2-] is maintained between 22 - 26 mEq/L with a
mean of 24 mEq/L
Blood pressure
Blood pressure is the pressure of blood traveling through the main
arteries of the body. Systolic pressure is measured when the ventricles of the heart are
contracting, diastolic pressure is measured when the ventricles are at rest. The blood
pressure levels vary with age. For a young adult, the healthy pressure averages 120
systolic and 80 diastolic. Blood pressure also varies temporarily with physical or
emotional stress and exercise. Hypertension is when the blood pressure is too high and
hypotension is when it is too low. The autonomic nervous system regulates the body's blood
pressure.
Blood volume
This is the amount of blood circulating throughout the body.
Blood Gas
A laboratory test that usually includes the pH, pO2, pCO2, Total CO2,
HCO3-.
Bohr effect
Describes the influence of carbon dioxide on the affinity of oxygen
binding affinity of hemoglobin. An increasing in the carbon dioxide level decreases the
oxygen binding affinity of hemoglobin.
Bradycardia
A heart rate, usually less than 60 bpm.
Bundle branches
The portion of the conduction system that from the bundle of His to the
Purkinje fibers. The Bundle of His splits into a right bundle for the right ventricle and
two left bundles for the left ventricle.
Bundle of His
Specialized conducting tissue that carries the electrical stimuli from
the AV Node to the ventricles. The Bundle of His splits into a right bundle for the right
ventricle and two left bundles for the left ventricle.
Bundle of Kent
An accessory pathway that exists between atria and ventricles and
causes early depolarization of the ventricle in Wolff-Parkinson-White syndrome.
C
Calcium channel blocker
A drug that blocks entry of calcium into cells and therefore, inhibits
the contraction of smooth muscle. It results in the dilation of blood vessels and
reduction in blood pressure.
Capillaries
The smallest blood vessels in the body. They branch from arterioles and
join to venules. The walls are only one cell thick. Capillaries allow exchange of oxygen,
nutrients, and other substance through their walls to the tissue beds, and removal of
carbon dioxide and waste products from the tissue beds into the blood stream.
Carbonic anhydrase
An enzyme found primarily in the kidney and red blood cells that
accelerates the reversible reaction of carbon dioxide (CO2) and water (H20) to form
carbonic acid (H2CO3-)
Cardiac arrest
Occurs is when the heart stops pumping blood. This can occur in
ventricular fibrillation when the ventricles are beating too erratically to effectively
pump blood, or in asystole because the heart stops beating completely. Cardiac arrest
victims quickly lose consciousness, their pulse disappears, and they stop breathing.
Emergency cardiopulmonary resuscitation (CPR) and defibrillation is necessary.
Cardiac output
The volume of blood pumped by the left ventricle over one minute.
Cardiac output is given by the heart rate multiplied by the stroke volume.
Cardiac muscle
(see myocardium)
Cardiogenic shock
Cardiogenic shock is the failure to maintain enough blood to maintain a
normal body blood pressure (and supply adequate blood to the tissues) because of
inadequate cardiac output, for instance in myocardial infarction. Cardiogenic shock can
result in fainting, organ failure or death.
Cardiovascular system
Refers to the heart and all the blood vessels.
Catecholamine
A group of neurotransmitter that includes dopamine, epinephrine and
norepinephrine. These neurotransmitters are found in the CNS and the sympathetic nervous
system
Central venous pressure
Cholesterol
Fat related compound that occurs naturally and plays a vital role in
metabolism. However, high cholesterol is a risk factor in coronary artery disease. It
results in fatty deposits on arterial walls and an increased blood pressure. The
recommended daily intake of dietary cholesterol is less than 200 - 300 mg. per day.
Chronic constrictive pericarditis
See pericarditis
Compensation
The process where one acid-base imbalance offsets another imbalance in
an effort to bring the pH back within normal limits. For example metabolic acidosis with a
[HCO3-] causes rapid ventilation causing respiratory alkalosis, a decreased in the pCO2 to
less than 35 mmHg.
Congenital defects
Congenital defects are organ defects present at birth.
Congestive heart failure
Global failure of the heart to maintain adequate circulation of blood
due o loss of pumping ability. It is generally accompanied by fluid accumulation in body
tissues and lungs. As a consequences patients have hypotension, difficulty breathing and
edema. Severe cases result in death.
Coronary arteries
The arteries of the heart. Blood flows into the coronary arteries
during diastole.
Coronary sinus
The opening into the right atrium to which the veins of the left
coronary circulation drain deoxygenated blood before it flows into the right atrium.
Coronary artery disease
Refers to the atherosclerotic narrowing of the major coronary
arteries.
Coronary thrombus
A blood clot that obstructs a blood vessel of the heart, blocking the
supply of blood to a section of the heart. The resulting lack of blood may cause a
myocardial infarction or death of that section of the heart muscle.
Cyanosis
Cyanosis occurs when blood is the arteries is carrying inadequate
oxygen. A blue tint appears in the patient's skin.
D
Descending aorta
Portion of the aorta that begins after the aorta arches. The descending
aorta travels down along the spinal cord. The section of the descending aorta from the
aortic arch to the diaphragm is the also called the thoracic aorta. The section of the
descending aorta below the diaphragm is also called the abdominal aorta.
Defibrillation
Defibrillation is the method by which an electrical shock is delivered
to the heart through externally applied electrode paddles or pads placed on the chest to
terminate fibrillation (ineffective, uncoordinated, chaotic muscular contractions of the
heart).
Depolarization
Change of the electrical polarity of a membrane because of flow of ion
in and out of the cell across the cell membranes. In the heart in sinus rhythm, it is
caused by electrical impulses arising from the SA node.
Diastole
Refers to the resting phase of the cardiac cycle when the ventricles
relax and fill with blood between contractions (see also blood pressure).
Digitalis
A medication that increases the force of heart contraction and slows
down the heart rate. It is a calcium blocker that slows the outflow of intracellular
calcium during contractions.
Dyspnea
Shortness of breath or difficulty breathing .
E
Echocardiography
Recording sound waves bounced off the heart to visualize cardiac
activity and produce images of the heart structure.
Electrocardiogram
EKG or ECG is the recording of the electrical activity of the heart
taken by a machine called an electrocardiograph.
Electrolyte imbalance
Ejection fraction
The percent of the left ventricular volume that is ejected in one
contraction of the ventricule. It is calculated as stroke volume divided by ventricular
end-diastolic volume.
Embolus
A small particle of blood, clot, fat or air that travels through the
bloodstream and lodges in small vessels.
Embolism
An embolism occurs when an embolus traveling though the blood stream
and lodges in a small vessel to block blood flow (see also pulmonary embolism).
Endothelium
The lining of blood vessels, heart and lymphatic system.
Endocarditis
An inflammation of the endocardium (the lining of the heart) and
valves, frequently caused by a bacterial infection. Symptoms include fever, heart murmurs
and heart failure.
Endocardium
The inner lining of the heart, arteries, veins and valves. Folds of
this linings form the cusps of the heart valves.
Endomyocarditis
Inflammation of the muscle and lining membrane of the heart. Symptoms
include arrhythmias, enlargement of the heart and murmurs.
Epicardium
The outer layer of the heart and the inner layer of the pericardial sac
surrounding the heart.
Erythropoiesis
Process by which the bone marrow produces red blood cells and other
cellular blood elements.
Extravascular
Outside of the vascular system, for instance, fluid in the interstitial
space.
F
Fibrillation
Rapid, chaotic heart beats that makes the heart ineffectively in
pumping blood. It can affect with the atria (atrial fibrillation) or ventricles
(ventricular fibrillation).
Fibrin
Fibrin is an insoluble protein that forms clots. It is formed by the
action of thrombin on fibrinogen.
Fibrinogen
Fibrinogen is a protein produced in the liver, and secreted into the
blood. It is the precursor to fibrin in the clotting process.
Fistula
A duct or passage formed by the imperfect closing leading from one
organ to either the body surface or to another hollow organ. Fistulas can also be formed
surgically.
G
Great vessels
Refers to the large arteries and veins arising from the heart.
H
Haldane effect
The haldane effect is the influence of oxygen on the affinity of
hemoglobin to bind with carbon dioxide. Increasing the oxygen level decreases the affinity
of hemoglobin for carbon dioxide.
HCO3-
See bicarbonate.
Heart attack
Refers to either cardiac arrest or myocardial infarction.
Heart block
Heart block occurs when the heart beats too slowly because of a problem
with the conduction of electrical impulses from the sinoatrial node. There are varying
degrees of heart block. In complete heart block (or third degree heart block) the
electrical impulses stop completely and the ventricles beats at their slow base rate of
20-40 beats per minute (versus a healthy average of 70 beats per minute). Causes of heart
block include congenital heart disease, death of heart muscle (myocardial infarction),
myocarditis, diseased valves, and scarring of the electrical conductive tissue of the
heart. An artificial pacemaker can restore the heart's rhythm.
Heart failure
Loss of the ability by the heart (ventricles) to pump blood. Therefore,
blood begins to stagnate in the tissues, causing back pressure. This back pressure results
in swelling of veins in the body and neck, edema, lung congestion and breathlessness. In
cases where not enough blood reaches the vital organs of the body, cardiogenic shock
results. Causes of heart failure include coronary thrombosis, myocardial infarctions,
diseased valves and arrhythmias.
Hematocrit
The percent of the blood that is cellular elements. Hematocrit is
normally 35-45 % of blood.
Hemoglobin
Red pigmented complex protein found in the red blood cells. It's
function is to transport oxygen and carbon dioxide.
Hemolysis
Normal breakdown or mechanical destruction of the red blood cell
releasing hemoglobin.
Hemostasis
Coagulation mechanisms to stop bleeding.
Heparin
A negatively charged polysaccharide found that naturally prolongs the
time it takes blood to clot by catalyzing anti-thrombin III. It is normally found in lung
and gut mucosa.
Homeostasis
Maintenance of a normal physiological balance in a system.
Hydrogen ions
Protons or the ions released when an acid is dissolved in water (or
plasma). H+
Hypercapnea
Abnormally high CO2 level in the blood, pCO2 > 45 mmHg.
Hypercholesterolemia
Excessive cholesterol in the blood.
Hyperkalaemia.
High potassium (K+) concentration. It may result in atrial
fibrillation, ventricular fibrillation, wide QRS, and wide, tall T waves.
Hyperlipidemia:
Excessive quantity of cholesterol and triglycerides in the blood.
Hyperplasia
Enlargement of an organ due to increase in rapid cell division.
Hypertension
Increase of systolic and diastolic blood pressure above their healthy
range as determined by age. Causes of hypertension include clogged or narrowing of
arteries, kidney disease or unknown causes (essential hypertension). Severe cases of
hypertension can lead to heart failure.
Hypertrophy
Enlargement of an organ due to increase in size of its constituent
cells.
Hypervolemia
Increase of blood volume to above normal.
Hypokalaemia
Low potassium levels in the blood. May result in heart arrythmias. A
common sign of Hypokalaemia is slight depression of the ST segment or small or absent
T waves.
Hypotension
Decrease of systolic and diastolic blood pressure below normal range as
determined by age. It can be caused by a severe loss of blood, myocardial infarction,
pulmonary embolisms or arrhythmias. Symptoms include lightheadedness, fainting, sweats, a
weak pulse, and loss of circulation in the limbs.
Hypovolemia
Decreased blood volume below normal
Hypoxemia
Reduction of oxygen level in the blood below normal.
Hypoxia
Reduction of oxygen level in tissues below normal.
I
Inferior vena cava
Interatrial septum
A ridge of tissue between the two atria of the heart.
Interstitial
The space in the tissues between cells outside the vascular system.
Ischemia
When the need for oxygen exceeds the supply of oxygen leading to tissue
damage and/or necrosis.
Ischemic heart disease
Result from myocardial ischemia due to atherosclerotic cardiovascular
disease, when the need for oxygen exceeds the supply of oxygen to the heart..
J
Junctional rhythm
A heart rhythm initiated in the AV node in the event of SA node
failure. The AV node can act as a secondary pacemaker for the heart in the event of SA
node failure. Junctional rhythm is usually at a rate of 40-60 bpm.
L
Left atrium
Left ventricular function
The function of the left ventricle which receives blood from the left
atrium and pumps it out into the general circulation through the aortic valve.
Left ventricular hypertrophy
Long QT interval
A QT interval longer than 0.42 seconds. The QT interval normally varies
with heart rate, becoming shorter at faster rates. See also QT interval.
M
Macro reentrant circuits
Rhythm disturbances characterized by large circular electrical patterns
or wavelets that occur in atrial flutter, atrial fibrillation, ventricular fibrillation
and Wolff-Parkinson-White syndrome.
Mean arterial pressure
Mediastinum
The mass of tissues and organs separating the sternum in front and the
vertebral column behind. It contains the heart and its large vessels, trachea, esophagus,
thymus and lymph nodes.
Metabolic
Intracellular chemical reactions to produce energy.
Metabolic acidosis
Increase in acid or primary loss of bicarbonate from the extracellular
fluid. Reflected by a low pH and low HCO3-, less than 22 mEq/L.
Metabolic alkalosis
Increase of base or loss of acid from the extracellular fluid.
Reflected by a high pH and high HCO3-, greater than 26 mEq/L.
Mitral
The bicuspid valve separating the left atrium and ventricle to prevent
back flow into the atrium during ventricular systole.
Mitral insufficiency
Abnormal back flow or regurgitation of flow through the mitral valve
during ventricular systole.
Mitral regurgitation
Abnormal back flow of blood from the left ventricle into the left
atrium, resulting from imperfect closure of the mitral valve.
Mitral stenosis
Narrowing of the normal area of the mitral valve causing a pressure
drop across the valve during left ventricular filling
Murmur
Abnormal sound made by blood that is flowing irregularly, or
turbulently in the heart or arteries. May be caused by a narrowed vessel or valve, a
leaking valve, or too much blood flow through a normal vessel. The presence usually
requires further evaluation. Systolic murmurs occur when the heart is contracting.
Diastolic murmurs occur when the heart is relaxing. Continuous murmurs usually indicate
abnormal communications between arteries and veins or between the aorta and other parts of
the heart.
Myocardial ischemia
Condition in which oxygen demand exceeding supply such that oxygen
delivery to and waste removal from the myocardium falls below normal levels.
Myocardial infarction
Damage to the heart muscle caused by occlusion of one or more of the
coronary arteries.
Myocardium
Specialized muscles that comprises most of the walls of the heart.
Cardiac muscles have intercalated disks between the muscle fibers to allow rapid
conduction of electrical impulses. They work continuously throughout the organisms life.
They contract to pump blood throughout the body at a rhythm dedicated by the SA node.
N
Normal sinus rhythm
The normal cycle of electrical stimulation of the heart that begins in
the sinoatrial node (SA node), traveling to the left atrium and down to the
atrioventricular node (AV node) and then continues to down the bundle of His and splits
into three bundle branches in the ventricles. The electrical stimulation of the heart is
necessary to produce the muscular contraction that is responsible for the pumping action
of the heart. The normal sinus rhythm is description on an EKG as each P wave is followed
by a QRS, heart rate >60 and <100
P
P50
Hemoglobin P50 is the partial pressure of oxygen where hemoglobin is
50% saturated with oxygen, normally about 27 mmHg.
P wave
A small rounded wave on an electrocardiogram (EKG) that indicates
atrial contraction.
Pacemaker
A device that provides the electrical stimulation to cause the heart
muscle to contract. A pacemaker can be either temporary or permanent depending upon the
need of the patient and it can function either as the primary stimuli for the heart, or it
can be used in a backup mode.
Parasympathetic nervous system
A major part of the autonomic nervous system, mediated by the vagus
nerve. Tends to slow down the heart rate
Parasympathetic tone
Abnormal increase in the activity of the vagus nerve which can cause
bradycardia (a slowing-down of the heart) with resulting dizziness and/or fainting. This
response (known as a vagovagal reflex) can sometimes occur as a result of irritation or
pressure to the larynx (back of throat/voicebox) or trachea (windpipe).
Partial pressure
The pressure exerted by a gas dissolved in plasma or blood in mmHg, for
example pO2 is the partial pressure exerted by dissolved oxygen. Partial pressure can be
used to tell the amount of that gas dissolved in the blood.
pCO2 (paCO2)
The partial pressure (tension) exerted by CO2 in mmHg. The amount of
CO2 dissolved in the blood is measured by the partial pressure it exerts and is reported
in mmHg. pCO2 is a measurement of the ventilation status of the patient.
Pericardium
The tough non-elastic membrane surrounding the heart that attached to
the great vessels and other anatomical structures in the mediastinum. The pericardium is
lubricated, protecting the heart from friction.
Pericarditis
Inflammation of the pericardium. Among the causes of pericarditis are
viral infection and cancer. Pericarditis can results in fever, chest pain, and the
build-up of too much fluid in the sac, known as pericardial effusions. Rarely, the
pericardium thickens in chronic constrictive pericarditis, interfering with the
functioning of the heart.
Pericardial effusions
See pericarditis
Peripheral vascular resistance
Resistance to the flow of blood through the peripheral vascular
beds
pH
The inverse log of the hydrogen ion activity. Used as a measure of the
alkalinity or acidity of the blood or solution on a 14 point scale with 1 being acidic and
14 being alkaline. The body normally pH is maintained within very strict limits. Normal pH
is 7.35 - 7.45 with a mean of 7.40.
Plasma
The acellular, colorless liquid portion of the blood
Plasmin
The substance found in the blood that digests fibrin resulting in clot
dissolution
Plasminogen
The precursor to plasmin that is activated by tissue plasminogen
activator (TPA)
pO2
The partial pressure of oxygen. A constant supply of oxygen is needed
to maintain living tissue. 21% of the air we breath is oxygen and at sea level it exerts a
pO2 of ~159 mmHg. The air is taken into lungs with each inhalation and moved into the
alveoli where the pO2 is ~100 mmHg. The O2 diffuses into the blood and dissolves in the
plasma where it exerts a pO2 of ~95 mmHg. In normal arterial blood with a pO2 of ~95 mmHg
the blood is ~98% saturated with oxygen. The oxygen is carried to the tissue by the blood
and by the time the venous blood returns to the lungs it has a pO2 of ~40 mmHg and is ~75%
saturated. The paO2 is assessed to provide a measure of the arterial oxygenation.
Polycythemia
A medical condition characterized by too many red blood cells in the
circulation.
Polymorphous ventricular tachycardia
See Torsade de pointes
Premature atrial contraction
PR interval
The interval of time between the P wave and the R wave on the ECG
PT
Prothrombin time
PTT
Partial thromboplastin time
Pulmonary artery
Carries deoxygenated blood from the right ventricle to the lungs. The
pulmonary artery splits into a left and right branches, one for each lung. The pulmonary
artery is the only artery in the body that carries oxygen-poor blood.
Pulmonary circulation
Refers to the blood vessels connecting the heart and the lungs, that
is, pulmonary arteries and veins.
Pulmonary embolisms
Blocks of the pulmonary arteries caused by a blood clot logging into
the small pulmonary arteries
Pulmonary hypertension
Occurs when the blood pressure in the blood vessels supplying the blood
to the lungs is too high. This increased pressure causes the right ventricle of the heart
to become enlarged, and may result in fainting, chest pain and heart failure. Other
possible complications include, embolisms, septal defects, mitral valve diseases, and
chronic lung diseases.
Pulmonary veins
Carry oxygenated blood from the lung to the left atrium. They are the
only veins in the body that carry oxygen-rich blood. They are also the only blood
vessels that have cardiac muscle.
Pulmonary valve
Pulmonary stenosis
Pulmonary valvular stenosis; narrowing of the normal area of the
pulmonary valve causing a pressure drop across the valve during left ventricular
systole
Q
QRS complex
EKG representation of the heart's electrical impulse as it passes
through the ventricles.
QT interval
An EKG measurement of the time between ventricular depolarization and
repolarization.
R
R - R interval
The interval from the peak of one QRS complex to the next. It is used
as an indicator of regularity when evaluating the heart's rhythm on an EKG
Refractory period
The period following depolarization of the heart's muscle cells during
which the cardiac cells cannot be reactivated until repolarization has been completed.
Repolarization
The restoration of electrical polarity via an increase in ion
differential between the cell membranes of the myocardium. It is necessary in preparation
for the next heart beat
Right atrium
Right bundle branch block
Right coronary artery
Respiration
The chemical processes at the tissue cellular level that converts
carbohydrates, oxygen and water to heat, ATP and carbon dioxide
Respiratory acidosis
An abnormal physiological process in which there is a reduction in
alveolar ventilation relative to the rate of CO2 production. It is reflected by a high
pCO2 (pCO2 > 45 mmHg) and low pH. Treat by increasing ventilation.
Respiratory alkalosis
An abnormal physiological process in which there is an increase in the
rate of alveolar ventilation relative to the rate of CO2 production. Reflected by a low
pCO2 (pCO2 < 35 mmHg) and high pH. Treat by decreasing ventilation.
Retrograde
Electrical impulse travelling opposite the normal direction of flow,
for instance from the AV node backwards to activate the atria.
Right ventricle
S
SA node (sinoatrial node)
A cluster of special muscle fibers located in the right atrial wall of
the heart considered to be the primary pacemaker of the heart. It normally generates
regular electrical impulses that cause the heart muscle to contract.
Shock
An acute peripheral circulatory failure due to decreased cardiac
output, poor circulatory control (heart ineffective in pumping) or loss of circulating
fluid. It is marked by hypotension, tachycardia, coldness of skin and anxiety.
Sinoatrial node
Specialized heart muscle that serves as an pacemaker for the heart. The
sinoatrial node sends one electrical signal telling the atrium to contract and another
signal to the AV node for relay to the ventricles.
Sick sinus syndrome
A rhythm disturbance characterized by disruptions in the generation of
SA nodal impulses or conduction from the SA node. The SA node may be partially or totally
destroyed via inflammatory and/or degenerative processes. EKG characteristics include
sinus bradycardia, atrial fibrillation, supraventricular tachycardia (SVT), and sinus node
arrest. Treatment usually requires a permanent pacemaker
Sinus bradycardia
A heart rate of less than 60 beats per minute that originates in the SA
node
Sinus rhythm
The normal cycle of electrical stimulation of the heart that begins in
the sinoatrial node (SA node), traveling to the left atrium and down to the AV node. It
then continues to down the bundle of His and splits into the bundle branches to each
ventricle. The electrical impulse produce the muscular contraction of that heart that is
responsible for the pumping action of the heart.
Sinus tachycardia
A heart rate greater than 100 beats per minute that originates in the
SA node.
Stenosis
Narrowing or blockage of an artery, leading to a decreased blood flow.
Stenosis is usually caused by atheroma, fatty plaques and scar tissue that build-up on
artery walls.
Stroke volume
Sudden cardiac death
Cardiac arrest. Caused by an irregular heartbeat.
Supraventricular arrhythmia
An irregular heart beat that originates in the atria or AV node.
Superior vena cava
Supraventricular tachycardia
Sympathetic nervous system
Part of the autonomic nervous system that usually functions to excite
or speed up the systems it enervates. The sympathetic nervous system is responsible for
giving the opposite message as its counterpart, the parasympathetic nervous system.
Systemic circulation
Refers to blood flow through all of the blood vessels in the body
except those that supply the lungs.
Systole
Refers to the period of time during contraction of the ventricle(s),
when blood is ejected from the ventricles into the aorta and pulmonary artery
Systolic blood pressure
The blood pressure measured in the arteries during systole
T
Tetralogy of fallot (TOF)
Congenital heart condition characterized by an over riding aorta and
right ventricular outflow tract (pulmonary artery) obstruction.
Thrombus
A blood clot, usually formed at a site of injury to stop bleeding
Tricuspid atresia
Small or undeveloped tricuspid valve
Tricuspid valve
Tricuspid regurgitation
Tachycardia
Tachycardia is an increase of the heart rate above the normal level.
Usually, any heart rate that is greater than 100 beats per minute is tachycardia. Possible
causes are arrhythmias, illness, exercise, stress or excitement.
Torsade de pointes
Also known as polymorphous ventricular tachycardia. A form of
ventricular tachycardia where there are wide QRS complexes with multiple morphologies and
the axis seems to twist about the isoelectric line. There is also a changing R - R
intervals. Usually, it is reversible. Common causes include heart block,
hypokalaemia or hypomagnesaemia, drugs and a congenital long QT syndromes.
V
Vagal tone
Parasympathetic activity of the vagus nerve that causes a slowing-down
of the heart. Abnormal increase in the vagal tone can cause bradycardia resulting in
dizziness and/or fainting.
Valves
Flap-like structures that prevent the backflow of blood flow through
the heart or veins.
Vasoconstriction
A decrease in diameter of arterioles restricting blood flow to an organ
or portion of the body
Vasodilate
An increase in diameter of arterioles allowing more blood flow to
an organ.
Vein
A blood vessel that carries blood toward the heart. All veins, except
the pulmonary vein) usually carry deoxygenated blood.
Vena cava
The large veins collecting the venous return from the head, neck and
shoulders (superior vena cava) and the legs and gut (inferior vena cava). They drain into
the right atrium
Ventilation
The movement of gas in and out of the lungs to facilitate blood
oxygenation and carbon dioxide removal
Ventricle
A chamber in the heart which pumps blood either from the right
side of the heart through the pulmonary trunk and arteries to the capillaries of the lung,
or which pumps oxygenated blood into the aorta to all the tissues of the body
Ventricular fibrillation
Ineffective, uncoordinated muscular contractions of the heart's
ventricles. Can lead to cardiac arrest or myocardial infarction.
W
Wolff- Parkinson-White (WPW) syndrome
An atrioventricular conduction disorder, characterized by the presence
of two separate atrioventricular conduction pathways. It can be identified by the presence
of a slurred upstroke to the QRS indicating a "delta" wave on the EKG, a short
PR interval and a broad QRS. An accessory pathway, bundle of Kent, exists between atria
and ventricles and causes early depolarization of the ventricle.
