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Chapter 13
Cardiology and the
Cardiovascular System
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
What is Cardiology?
• Cardiology: The medical specialty dealing with the
diagnosis and treatment of disorders of the heart
• Latin: cardium
Greek: kardia
• Heart’s primary purpose: To supply the body with blood
and oxygen it needs to function properly
• Pumps blood through a closed circuit of vessels in a
continuous loop, carrying oxygen and nutrients from the
heart to parts of the body and deoxygenated blood back
to the heart to be reoxygenated
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The Cardiovascular System
• Blood vessels—A network of interconnecting arteries,
arterioles, capillaries, venules, and veins—provide the
pathway through which blood is transported between the
heart and body cells. Functions:
–
Arteries and arterioles – distribute
–
Capillaries – exchange
–
Veins and venules – collect
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• Arteries: Carry blood away from the heart to supply
organs and tissues with oxygen and nutrients
• Arterioles: Smaller arteries which adjust their diameter
to increase or decrease blood flow to a particular body
tissue
• Capillaries: Allow oxygen and nutrients to pass from the
blood in the arterioles into tissues and allow waste
products to pass from tissues into the blood.
• Venules: Small vessels that gather blood from the
capillaries
• Veins: The larger vessels that carry deoxygenated blood
back to the heart
•
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Anatomy of The Heart
• The heart is composed almost entirely of muscle
• Two Different Pumps:
– Pumps deoxygenated blood into the lungs to
gather oxygen
– Pumps oxygenated blood from the lungs
throughout the body
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• Pericardium
– Surrounds the heart like a sac
Layers:
– Epicardium – outer layer
– Myocardium – middle layer
– Endocardium – inner layer
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• Chambers: Sections through which blood is
pumped
– Right atrium (upper chamber)
– Left atrium (upper chamber)
– Right ventricle (lower chamber)
– Left ventricle (lower chamber)
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• Valves: Open and close to maintain blood flow
through the heart
– Tricuspid valve – between right atrium and right
ventricle
– Mitral valve – between left atrium and left ventricle
– Pulmonary valve – between the right ventricle and
pulmonary artery
– Aortic valve – between the left ventricle and the
aorta
• Leaflets: Prevent backflow of blood during
heartbeat
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• Coronary arteries: A network of blood vessels that
supply oxygen- and nutrient-rich blood directly to the
heart’s muscle tissue
– Aorta: The main arterial line
• Right coronary artery (RCA)
• Left coronary artery (LCA)
– Posterior descending artery (PDA): Main branch of the RCA
– Left main coronary – branches off LCA
• Left anterior descending artery (LAD)
• Left circumflex artery (LCA)
– Two diagonal branches (D1 and D2)
– Two obtuse marginal branches (OM1 and OM2)
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Cardiovascular Circulation
• There are two major pathways of the vascular circulation
of blood in the body: pulmonary and systemic
– Pulmonary circulation is the part of vascular
circulation that begins at the right ventricle of the
heart
– Systemic circulation is the part that begins at the
left ventricle
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• Pulmonary circulation: The right ventricle contracts and
pumps blood into the main pulmonary artery, branches
off into right and left pulmonary arteries, which deliver
deoxygenated blood to the corresponding lung.
• In the lungs, each artery branches into smaller arteries
and arterioles, and then to capillaries. Gas exchange of
oxygen and carbon dioxide takes place between the
pulmonary capillaries and the alveoli of the lungs. The
oxygenated blood is then returned to the left atrium. This
oxygenated blood then travels through the systemic
circulation to the rest of the body and the pulmonary
circulation begins again.
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• Systemic circulation: The left ventricle pumps blood into
the aorta, which branches off into other arteries that take
oxygenated blood into arterioles and capillary networks
throughout the body.
• After exchange of oxygenated blood and waste products,
the deoxygenated blood is sent back to the heart via the
superior vena cava and the inferior vena cava. Blood in
the right atrium empties in to the right ventricle, and the
process starts again.
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The Cardiac Cycle
• Cardiac Conduction: The name given to the electrical
conduction system that controls the heart rate
– Provides the electric stimulus necessary for heart to beat
• Cardiac Cycle: The sequence of events in one heartbeat
– The right and left atria accept blood returning to the heart
from the body
– The two ventricles push blood out of the heart to be
circulated throughout the body
– Contraction phase: Systole
– Relaxation phase: Diastole
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Process:
– Electrical stimulus from the sinoatrial (SA) node, “the
heart’s natural pacemaker”
– To the atrioventricular (AV) node – acts as a bridge
between the atria and ventricles in regulating the
electrical impulse from the SA node
– To the bundle of His – fiber bundles that carry
impulse throughout the ventricles
– To the left and right bundle branches (pathways)
– To the Purkinje fibers – microscopic muscle branches
which trigger the ventricles to contract and push
blood out into the lungs and body
– Cycle begins again
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Heart Sounds
• Heart sounds: Vibrations in the tissues and blood caused
by closure of the heart valves
– Lub-dub: Healthy sound, called first heart sound (S1,
the lub) and second heart sound (S2, the dub)
– Murmurs: Abnormal heart sounds
• Graded based on degree to which they are audible
• Six-point grading system, with 1 being barely
detectable and 6 being very loud
• Expressed with a slash between murmur grade and
scale used (e.g., grade 1/6 murmur)
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• A rub is an abnormal sound that is caused by the friction
between the beating heart and the pericardium and resembles
the sound of squeaky leather and often is described as grating,
scratching, or rasping.
• A gallop is a tripling or quadrupling of heart sounds that
includes three or four sounds that resemble the cantering of a
horse.
• A click, or systolic click, is a short, high-pitched sound heard
when a valve is not functioning properly and may be indicative
of valvular disease.
• A thrill is a high-frequency vibration felt on the chest wall over
the heart, which may be indicative of a structural defect of the
heart.
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Heart Rates and Rhythms
• Normal heart rate is about 60-80 beats per minute
(pulse), called sinus rhythm
• Arrhythmia: Lack of a normal heart rhythm (or
dysrhythmia)
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• Abnormal heart rates and rhythms
– Bradycardia: Slow heartbeat, less than 60 bpm
– Tachycardia: Fast heart rate, greater than 100 bpm
– Atrial flutter: Atrial rhythm is regular, but the rate is
abnormally fast
– Fibrillation: Uncoordinated, irregular contraction of the
heart muscle
• Atrial fibrillation
• Ventricular fibrillation
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– Heart block: Impaired conduction of the heart’s
electrical impulses
– Paroxysmal atrial tachycardia: A rapid heart rate that
starts and stops suddenly and unpredictably
– Premature atrial contraction: An extra heartbeat that
originates from the atria before it should
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• Blood Pressure
– Measures the force of blood against artery walls
– Sphygmomanometer: Measures blood pressure
– Indicated in terms of millimeters of mercury (mmHg)
and expressed as a fraction—e.g., 120/80
• Systolic pressure (top number): Maximum pressure on
the arteries as the heart contracts and pumps blood
into the arteries
• Diastolic pressure (bottom number): Minimum pressure
as the heart relaxes following a contraction
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• Hypotension: A blood pressure reading of 90/60 mmHg
or lower
• Orthostatic hypotension: The sudden temporary
decrease in systolic blood pressure that occurs when a
person changes position, resulting in a feeling of
lightheadedness
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Common Cardiac Diseases and
Treatments
• Signs of heart problems
– Cyanosis: bluish tinge
– Pallor: paleness
– Edema: swelling of tissues
– Diaphoresis: excessive sweating
– Angina (angina pectoris): severe chest pain
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• Hypertension (high blood pressure): A condition in which
the pressure of the blood in the arteries is too high, possibly
damaging the heart and blood vessels
– Primary hypertension: No identifiable cause
– Secondary hypertension: Another known cause (disease)
Treatments:
– Diuretics: Eliminate extra sodium and fluid from the body
– Beta-blockers: Decrease heart rate and the amount of
blood the heart pumps out with each beat
– ACE inhibitors: Inhibit the formation of angiotensin II,
which narrows blood vessels
– Calcium-channel blockers: Decrease the force of the
heart’s pumping action
– ARBs: Reduce pressure like ACE inhibitors but without
some of the side effects
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• Coronary Artery Disease (CAD): Narrowing arteries
hinder blood supply to heart
– Also called cardiac ischemia: From ischi, to hold back
and –emia, blood
– Cause: Plaques (atherosclerosis) build up in arteries,
causing arteries to narrow and harden, reducing
blood flow, causing stenosis (narrowing), angina
pectoris (severe chest pain), and dyspnea
(shortness of breath)
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– Complications:
• Heart failure: The heart does not pump the way it
should
• Congestive heart failure (CHF): Heart’s weak
pumping action causes fluid buildup (congestion) in
the lungs and other body tissues
• Orthopnea: Breathing difficulties while lying down
• Paroxysmal nocturnal dyspnea (PND): A sudden
onset of breathing difficulty occurring at night. Term
breakdown:
• Paroxysmal – sudden onset of a symptom
• Nocturnal – pertaining to hours of night
• Dyspnea – difficulty breathing
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• Treatments for CAD:
– Nitrates (nitroglycerin): Relieve angina by dilating blood
vessels
– Antihypertensive medications
– Surgical interventions:
• Percutaneous transluminal coronary angioplasty (PTCA)
• Opens narrowed arteries using a catheter, a thin
flexible tube with a tiny balloon attached
• The balloon inflates in the artery, flattening the
plaque against the artery wall and enabling better
blood flow
• Stent is implanted at the site to keep the artery from
collapsing
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• Treatments for CAD (Continued)
– Surgical interventions:
• Coronary artery bypass graft (CABG): Restores
circulation when occluded, or blocked, coronary
arteries prevent normal blood flow to the heart
• Bypasses around the blockages are performed
using different vessels as grafts
• Greater saphenous vein in leg and thigh most
common, called a saphenous vein graft
• The new, healthy graft carries blood around the
blockage
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• Cardiomyopathy: Impairment in structure and function
of the myocardium
– Dilated cardiomyopathy: Enlargement of the heart
chambers
– Hypertrophic cardiomyopathy: Overgrowth of heart
muscle
– Restrictive cardiomyopathy: Ventricles stiffen and do
not fill normally
Treatment:
– Drug therapy (ACE inhibitors, anticoagulants,
diuretics)
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• Valvular Heart Disease: The heart’s ability to pump blood is
impeded due to valve malfunction
– Blood leaks back through valves that should be closed
(regurgitation)
– Mitral valve prolapse: The heart’s mitral valve bulges
slightly back into the left atrium when it closes, causing
regurgitation into the atrium
– Treatment: Not usually required but if severe, surgical
treatment to repair valve is performed
– Patients may be prescribed antibiotics before dental or
other procedures to prevent bacterial endocarditis, a
bacterial infection which could lead to deformity and
destruction of valve leaflets
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• Pericarditis: An inflammation of the pericardium that
surrounds the heart
– The amount of fluid between the inner and outer
layers of the heart increases, compressing the heart
and interfering with its function
– Pericardial effusion: Fluid accumulates in the
pericardial sac, putting pressure on the heart and
causing it not to fill adequately or pump properly
• Cardiac tamponade: Less blood leaves the heart,
causing dramatic drop in blood pressure.
Potentially fatal if not treated immediately!
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• Causes of pericarditis:
– Bacterial or fungal infection
– AIDS, cancer, or tuberculosis
– After a heart attack
• Dressler syndrome: Delayed onset of pericarditis
• Treatments:
– Mild cases heal on their own
– Pericardiocentesis: Drainage of excess fluid (also
called pericardial window)
– Pericardiectomy: Portion of diseased pericardium is
removed
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Congenital Heart Disorders
• Atrial septal defect (ASD): A “hole in the heart,” or
in atrial septum
– Treatment: Hole usually closes on its own
• Ventricular septal defect (VSD): A hole in the
ventricular septum
– Treatment: Hole usually closes on its own
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• Patent Ductus Arteriosus (PDA)
– Ductus arteriosus remains open (patent) after birth
– Treatment: Condition will resolve alone or with
corrective surgery
• Transposition of the Great Vessels
– Location of aorta and pulmonary artery (great
vessels) is switched
– Treatment: Arterial switch operation
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• Tetralogy of Fallot
– Too little oxygen in the blood, leading to cyanosis
– Combination of four defects:
• VSD
• Pulmonary stenosis
• Displaced aorta
• Right ventricular hypertrophy
– Treatment: Surgery to increase blood flow and
correct defects
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Diagnostic Studies and Procedures
• Blood Tests
– Cardiac risk factor testing: Evaluate risk of heart
disease or stroke
• C-reactive protein (CRP)
• Homocysteine
• Lipoprotein (a) or Lp(a) (dictated as “L, P, little A”)
• Cholesterol particle test
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– Lipid profile (total cholesterol, HDL and LDL)
– Blood sugar (glucose)
– B-type natriuretic peptide (BNP)
– Cardiac enzyme studies
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• Electrocardiogram (EKG)
– Analyzes electrical activity of the heart
– During the test, electrodes called leads are placed
on patient’s arms, legs, and chest wall
– The impulses detected by the leads are produce
graphic tracing of waveforms on paper strip
– Deviation in shape or interval of waveforms indicates
possible problem
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• Echocardiogram
– Uses ultrasound to examine heart anatomy
– Sound waves “echo” off cardiac structures
– Provides image of beating heart on a computer
screen
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• Cardiac Stress Test: Evaluates the heart when heart is
working
– Measured using Bruce protocol
– Expressed in metabolic equivalents (METS)
– Nuclear scan thallium
• Camera records thallium received by the heart
• Shows problems with blood flow and pumping
action
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• Cardiac Catheterization and Angiography
– Diagnose and treat heart disorders other than those
involving coronary arteries
– Radiopaque dye is inserted into coronary arteries to
view images of the blood vessels as the heart pumps
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• Multiple gated acquisition (MUGA) scan
– Determines if the left and right ventricles are
functioning properly
– Diagnoses abnormalities in the heart wall
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Insight
The Heart-Brain
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