OVERVIEW OF THE HEART

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OVERVIEW OF THE HEART ANATOMY And
ARRHYTHMIAS Presented by Linda and Livia
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www.vancouverhearthealth.com
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ANATOMY
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• The size of a fist
• Weighs between 250 and 350 grams
• It has 4 chambers
• Two superior chambers called Atria
• Right Atrium (RA) and Left Atrium (LA)
• Two inferior chambers called Ventricles
• Right Ventricle (RV) and Left Ventricle (LV)
• Sulci define the boundaries of the 4 chambers
• Coronary sulcus separates the atria from the
  ventricles
• Interventricular sulcus separates the left and
  right ventricles
• Sulci contain major arteries and veins for heart
  circulation

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• The heart has 3 layers
• Pericardium tough membranous sac that encloses
  and protects the heart (outermost layer of the
  heart)
• A thin layer of clear pericardial fluid inside
  the pericardium lubricates the external surface
  of the heart as it beats
• Inflammation of the pericardium - Pericarditis
• Myocardium thickest layer of the heart made
  of pure muscle and it gets damaged during a heart
  attack. It is responsible for contraction and
  relaxation of the atria and ventricles.
• Epicardium covers the outside of the
  myocardium. It is a thin layer made of connective
  tissue and fat.
• Endocardium innermost thin layer of tissue that
  lines the heart's chambers and valves. The
  cardiac conduction system is located in this
  layer of the heart.

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Overview of Valves and Blood Flow
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Heart Chambers, Valves, and Blood Flow

• The heart is a two pump system
• The right side of the heart collects blood from
  the periphery and pumps it through the lungs
  called Pulmonary circuit
• The left side of the heart collects blood from
  the lungs and pumps it throughout the body
  called Systemic circuit
• The left ventricle pumps the blood against the
  greater resistance to the body (more
  muscular)
• The right ventricle pumps the blood a relative
  short distance through the pulmonary circuit
  (less muscular)

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Valves

• The heart has 4 valves
• Atrioventricular valves
• Tricuspid valve controls the blood flow from RA
  to RV
• Bicuspid valve controls the blood flow from LA
  to LV
• These valves prevent the retrograde blood flow
  during ventricular contraction
• Semilunar valves
• Pulmonary valve lies between the RV and the
• pulmonary artery
• Aortic valve lies between the LV and the aorta
• The cusps of the semilunar valves prevent the
  back-flow of blood from the arteries to the
  ventricles

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Blood Flow

• Venous blood flows into the RA via the
  superior and inferior vena cava, coronary
  sinus, and anterior cardiac veins
• The RA free wall contracts, and blood flow
  moves through the tricuspid valve into the RV
• The RV free wall contracts, the tricuspid valve
  closes, and blood flows through the
  pulmonary valve into the pulmonary artery
  and the branches of that system
• Blood ultimately reaches the alveolar
  capillaries, where gas exchange occurs

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• Blood flows back to the LA via the pulmonary
  veins
• The LA free wall contracts, and blood flows
  through the bicuspid valve and into the LV
• The LV free wall contracts, the bicuspid valve
  closes, and blood flows through the aortic
  valve into the aorta and its branches, where it
  is distributed to the coronary circulation
  and the systemic circulation

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Heart Blood Supply
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• Only the endocardium gets direct blood supply
• The myocardium is too thick to permit
  adequate diffusion of nutrients and oxygen to
  the cardiac muscle cells and epicardium
• Coronary arteries originate from the aortic
  sinus at the base of the aorta
• Left coronary artery (LCA)
• Right coronary artery (RCA)
• LCA goes towards the left side of the heart
  before branching into
• Left anterior descending (LAD) coronary artery
• Circumflex artery (CxA)

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• The LAD artery supplies blood to the
  interventricular septum and
  anterior walls of both ventricles
• The CxA branches toward the left margin of the
  heart in the coronary sulcus and
  supplies blood to the
  laterodorsal walls of the LA and LV
• Both the LAD and CxA curve around the left
  ventricular wall and supply small
  branches that interconnect with the
  RCA
• The RCA supplies blood to the right side of the
  heart as it follows the AV
  (atrio-ventricular) groove
• It then curves to the back of the heart giving
  off a posterior interventricular artery
  (posterior descending artery
  - PDA)

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• The RCA and PDA have numerous branches that
  supply blood to the anterior, posterior,
  and lateral surfaces of the RV and to the RA
• After circulating through the coronary artery
  system and the myocardial capillaries, it is
  collected by the cardiac veins
• The blood then travels a path similar to that of
  the coronary arteries but in the opposite
  direction
• On the posterior side of the heart, the cardiac
  veins form an enlarged vessel ? coronary
  sinus, which empties the blood into the RA
• The smaller anterior cardiac veins also empty
  directly into the RA

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Conduction System of the Heart
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• Cardiac muscle has intrinsic properties ? no
  need for neural stimulation
• Cardiac cells interconnect end to end and form
  intercalated discs
• these discs allow electrical impulses to spread
  from cell to cell and cause the myocardium to act
  as a single unit
• Components of the Conduction System
• Sinoatrial node (SA node)
• Atrioventricular node (AV node)
• AV bundle (Bundle of His)
• Right and Left bundle branches
• Purkinje Fibers

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• The electrical impulse starts at the SA node
  (intrinsic pacemaker)
• The cells depolarize spontaneously at 60 to 80
  beats per minute at rest
• Electrical activity goes rapidly to AV node via
  internodal pathways through both atria
• Depolarization spreads more slowly across
  atria. Conduction slows through AV node to
  allow the atria to contract and fill the
  ventricles
• Depolarization moves rapidly through
  ventricular conducting system to the apex of
  the heart
• Depolarization wave spreads upward from the
  apex

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• Sympathetic nerves and hormones
  (neropinephrine and epinephrine) stimulate
  the atria and ventricles of the heart to beat
  faster ? chronotropic effect
• and more forcefully ? inotropic effect
• Parasympathetic nerves control the atria and
  slow the heart rate

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ECG changes during electrical events in the heart
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• The SA node initiates a depolarization wave at
  regular intervals in the atria which is
  represented by a P wave on an ECG
• The P wave represents both depolarization and
  contraction of atria
• When the wave of atrial depolarization enters
  the AV node, depolarization slows producing a
  brief pause time it takes for the blood to
  enter the ventricles
• Depolarization conducts rapidly through the
  Bundle of His and its subdivisions and into
  Purkinje fibers
• Depolarization of the ventricular myocardium
  records as a QRX complex

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• The horizontal segment of baseline that follows
  the QRS complex is the ST segment
• ST segment is horizontal, flat, and most
  importantly, it is normally level with other
  areas of the baseline
• If the ST segment is elevated or depressed
  beyond the normal baseline level, this is
  usually a sign of serious pathology that may
  indicate imminent problems
• ST segment represents the initial phase of
  ventricular repolarization
• The final T wave represents the final rapid
  phase of ventricular repolarization

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What Is Arrhythmia?

• Abnormal rhythm of the heart
• It can feel like a temporary pause and be so
  brief that it doesn't change your overall heart
  rate
• Or it can cause the heart rate to be too slow or
  too fast

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What are the signs of Arrhythmia?

• If brief it can have almost no symptoms ? it can
  feel like a skipped heart beat that you barely
  notice
• Or it can feel like a fluttering in the chest or
  neck
• If it lasts long enough the heart may not be able
  to pump enough blood to the body ? it can cause
  tiredness and light-headedness, or the person may
  pass out
• Tachycardia can lead to decreased cardiac out
  (heart is not able to pump blood effectively) ?
  can lead to shortness of breath, chest pain,
  light-headedness or loss of consciousness. In
  severe cases it can cause heart attack and death.

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Different Types of Arrhythmias

• Pacemaker of the heart ? SA node ? initiates
  depolarization of the myocardium
• Beats at its own inherent rate of 60 bpm to 100
  bpm
• Bradycardia ? slow heart rate lt 60 bpm
• Common in athletes ? ? stroke volume, ? heart
  rate
• Increased vagal stimulation ? release of hormones
  that slow down the heart rate
• Patients who receive drugs to slow down the heart
  rate
• Individuals who have disease of the sinus node
• Symptoms tiredness, dizziness, light-headedness
  or fainting
• Treatment electronic pacemaker

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• Types of Bradycardias
• Sick Sinus Syndrome
• malfunction in the SA node ? it fires too
  slowly due to increasing age or disease
• some medications can slow your heartbeat
• Solution
• treatment with medication or with an electronic
  pacemaker

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• Heart Block
• Interruption of the electrical signal to the
  lower chambers of the heart
• It may develop as a side effect of certain heart
  medications
• It may be idiopathic in nature
• Or may be due to other forms of circulatory
  diseases
• coronary artery disease
• cardiomyopathy
• rheumatic heart disease
• uncontrolled or untreated high blood pressure
• primary conduction system disease
• Complete AV block (3rd degree block) is usually
  due to a complication of a heart attack, but may
  the result of a heart surgery or infections of
  the heart muscle

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• Symptoms
• Llight-headedness, fatigue, or fainting
• Diagnosis
• By ECG
• Treatment
• Implanting an electronic pacemaker

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• Tachycardia ? fast heart rate ? gt 100 bpm
• Causes
• stimulation of the heart by sympathetic nerves
• increased body temperature
• or toxic conditions of the heart
• Factors that affect SNS stimulation of the
  heart
• blood loss that results in a shock or semishock
• weakening of the myocardium

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• Supraventricular Tachycardia (above the
  ventricle)
• rapid heartbeat in the atria or AV node
• Atrial flutter
• Atrial fibrilation
• Paroxysmal supraventricular tachycardia
• Wolf-Parkinson-White Syndrome

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• Atrial Flutter ? 250 to 350 atrial
  depolarization per minute
• Due to back-to-back identical atrial
  depolarization waves
• Usually not life threatening
• Can cause chest pain, faintness, or others more
  serious problems

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• Atrial Fibrillation ? multiple foci discharge
  rapidly at 350-450/min
• Very common dysrhythmia
• Results in ? cardiac output
• Usually not life threatening
• Causes light-headedness or palpitations
• It increases the risk of stroke

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• Symptoms of Atrial fibrillation
• Irregular and fast heart beat
• Heart palpitations and rapid thumping in the
  chest
• Chest discomfort, chest pain or pressure
• Shortness of breath, particularly with exertion
  or anxiety
• Fatigue
• Dizziness, sweating, or nausea
• Light-headedness or fainting

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• Causes of Atrial fibrillation
• In most cases idiopathic in nature
• Age
• High blood pressure
• Infection or inflammation of the heart
• Valvular heart disease
• Ischemic heart disease
• Cardiomyopathy
• Conduction system disease
• Overactive thyroid
• Pulmonary embolism
• Hypoxia
• Holiday heart syndrome

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• Treatment of Atrial fibrillation
• Blood thinners to decrease the risk of stroke
• Rhythm control therapy
• medication to prevent atrial fibrillation from
  occurring
• electrical cardioversion
• ablation
• maze procedure
• Rate control therapy
• medication to slow down the heart rate
• Digitalis
• Calcium channel blockers (diltiazem and
  verapamil)
• Beta-blockers

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• Treatment of Atrial fibrillation
• Blood thinners to decrease the risk of stroke
• Rhythm control therapy
• medication to prevent atrial fibrillation from
  occurring
• electrical cardioversion
• ablation
• maze procedure
• Rate control therapy
• medication to slow down the heart rate
• Digitalis
• Calcium channel blockers (diltiazem and
  verapamil)
• Beta-blockers

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• Paroxysmal supraventricular tachycardia ?
  140-250/minute
• Involves atria or AV node
• Usually occurs in young, healthy people
• May be distressing and can cause weakness during
  the paroxysm
• Rarely life threatening

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• Can occur with digitalis toxicity and Wolf-
  Parkinson-White Syndrome
• The following increases your chance for PSVT
• Alcohol use
• Caffeine use
• Illicit drug use
• Smoking
• Symptoms
• Anxiety
• Chest tightness
• Palpitations and rapid pulse
• Shortness of breath
• Dizziness and fainting

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• Treatment
• Valsalva maneuver
• Cough while sitting with your upper body bent
  forward
• Splashing ice water on face
• Ablation
• Cardioversion
• Medications
• Pacemaker
• Wolf-Parkinson-White syndrome

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Ventricular Arrhythmias

• Premature Ventricular Contractions
• Ventricular Tachycardia
• Ventricular Fibrillation
• Long QT syndrome

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• Premature ventricular contractions ? a site in
  the ventricle fires before the next wave of
  depolarization from the sinus node reaches
  the ventricle
• These are bizarre looking complexes
• Relatively benign ? often occurs in healthy
  hearts during rest and exercise ? occasional
  PVC's
• Causes cigarettes, excessive coffee intake, lack
  of sleep, various mild toxic states, and
  emotional irritability
• Many PVC's may be markers of underlying cardiac
  disease such as infarcted or ischemic areas of
  the heart and can develop into lethal
  ventricular fibrillation

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• Ventricular tachycardia ? three or more
  consecutive ventricular beats at 100 bpm or
  faster
• Non-sustained ventricular tachycardia lasts less
  than 30 seconds
• Sustained ventricular tachycardia lasts more than
  30 seconds
• Wide QRS complex, AV dissociation
• A serious condition ? occurs due to considerable
  ischemic damage that is present in the ventricles
• ? initiates the lethal condition of ventricular
  fibrillation
• Treatment ICD, ablation, medications - quinidine

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• Ventricular fibrillation ? 250-350/minute
• Serious of all cardiac arrhythmias
• If not stopped within 1 to 3 minutes it is fatal
• It's not a coordinate contraction of all the
  ventricular muscle at once
• The ventricular chambers neither enlarge nor
  contract but remain in an indeterminate stage
  of partial contraction ? loss of consciousness
  within 4 to 5 seconds due to lack of blood flow
  to the brain

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• Causes
• Sudden electrical shock of the heart
• Ischemia of the heart muscle
• Treatment
• CPR
• Defibrillation

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• Long QT syndrome
• Normal QT interval is less than half of the
  R-to-R interval at normal rates
• Usually hereditary due to mutations of sodium or
  potassium channel genes
• Acquired forms include hypomagnesemia,
  hypokalemia, or hypocalcemia, or excess
  amounts of antiarrhythmic drugs such as
  quinidine or some antibiotics
• Symptoms
• no major symptoms present
• fainting and ventricular arrhythmias due to
  exercise, intense emotions, or when startled
  by a noise
• Treatment
• magnesium sulfate for acute LQTS
• beta blockers, or ICD for long term LQTS

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• Long QT syndrome
• Delayed repolarization of ventricular muscle can
  lead to ventricular arrhythmia called Torsades de
  pointes ? if unresolved, it can lead to a deadly
  arrhythmia

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What to do if you think you have an undiagnosed
Arrhythmia?
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• Check your heart rate and blood pressure on
  regular basis
• Check your family history
• Screening ? looking for disease before there are
  symptoms
• Seek medical help ? your family doctor
• Your doctor will review your medical history
  including a physical exam
• He/she may send you for further testing
  including
• An electrocardiogram (ECG)
• Exercise electrocardiogram (Stress test)
• Holter monitor

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How is Arrhythmia Treated?

• Life-style changes
• Avoiding stress, cutting out alcohol and
  caffeine, eating healthy diet, being more
  physically active
• Medications
• Digitalis/digoxin, beta blockers, calcium channel
  blockers
• Surgery or other non-surgical techniques
• Ablation
• Cardioversion therapy
• Implantable pacemaker
• Ventricular resection or remodeling

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THE END