Basic Principles of the Cardiovascular System

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Basic Principles of the Cardiovascular System

• Patient Care Techncian

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Objectives

• Describe the structures of the heart.
• Explain the pumping mechanism of the heart and
  the path of blood flow through the heart.
• Distinguish between pulmonary circulation and
  systemic circulation.
• List the components of the conduction system and
  the sequence of impulse origination.
• State four properties of cardiac cells.

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Anatomy of the Heart

• 4 chambered pump
• Weighs less than 1 pound
• Size of closed fist
• Located in mediastinum between lungs, sternum,
  spine

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Chambers
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Valves
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Question

• The right side of the heart pumps just as much
  blood as the left side why are the walls of the
  right side thinner than those of the left?

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Where are these valves?

• Tricuspid valve
• Mitral valve
• Pulmonary semilunar valve
• Aortic valve

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Chordae tendoneae
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Heart Layers
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Heart Layers

• Endocardium layer of smooth cells that line
  heart
• Myocardium layer of muscle that cause
  contraction (myocardial infarction)
• Epicardium fatty layer that protects heart
• Pericardial sac holds heart in place, reduces
  friction of beat

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Circulation

• Pulmonary
• Systemic
• Coronary

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Pulmonary Circulation
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Pulmonary Circulation
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Systemic Circulation
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Coronary Circulation
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Coronary Circulation
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Coronary Circulation

• Anterior (A) and posterior (B) views of
  epicardial coronary circulation. LAD indicates
  left anterior descending coronary artery AIV,
  anterior interventricular vein CFX, circumflex
  coronary artery RCA, right coronary artery GCV,
  great cardiac vein PDA, posterior descending
  artery CS, coronary sinus MCV, middle coronary
  vein and SCV, small coronary vein.

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Question

• Where and when do coronary arteries fill?

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Coronary Sinus
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Blood Vessels

• Define the following
• Artery
• Arteriole
• Vein
• Venule
• Capillary
• Aorta
• Vena Cava
• Pulmonary artery
• Pulmonary vein

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Question

• What vessels, structures and/or organs are
  included in each type of circulation?

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Question

• Show the path of a drop of blood from the right
  atrium back to the right atrium.
• Be sure to include major vessels, organs, and
  valves.

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Cardiac cycle

• Series of events that constitute complete
  heartbeat
• Atrial systole - Contraction of atria to pump
  blood to ventricles
• Ventricle systole contraction of ventricles to
  pump blood to body
• Atrial diastole the atria begin refilling
  during ventricular systole
• Ventricular diastole blood from the atria
  begins refilling the ventricles during atrial
  systole.

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Conduction Pathways

• Network of conducting tissue
• Specialized cells do not contract
• Initiates each heartbeat and controls rhythm

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Sinoatrial Node

• Located in right atrium
• Main cardiac pacemaker
• Normally generates impulses at rate of 60 to 100
  beats per minute

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Atrioventricular Node

• Receives impulse via internodal pathways
• Located in floor of atrium near septum
• Delay the impulse to allow ventricular filling
• Intrinsic rate 40 to 60
• Two basic functions
• Protect ventricles from fast heart rate that may
  originate in atrium
• Serves as pacemakers if SA node fails

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AV Bundle or Bundle of His

• Conducts impulse from AV Node
• Divides into right and left bundle branches at
  intraventicular septum
• Right bundle branch supplies right ventricle
• Left bundle branch splits
• Anterior supplies upper portion of left ventricle
• Posterior supplies lower portion of left ventricle

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Purkinje Fibers

• Enlarged fibers
• Spread along septum toward apex and over lateral
  walls of ventricles
• Work with Bundle of His and bundle branches to
  contract ventricles
• Intrinsic rate 20 to 40
• May act as backup pacemaker

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Cardiac Electrical System
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Cool Website!

• http//science.howstuffworks.com/environmental/lif
  e/human-biology/heart4.htm

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Special Properties of Cardiac Cells

• Automaticity ability to generate own impulse
  and maintain rhythmic activity
• Excitability ability of all heart cells to
  respond to impulse
• Conductivity cardiac cell able to relay impulse
  to neighboring cells and create wave of
  excitation
• Contractility ability to respond to electrical
  impulse with pumping action

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Two Types of Cardiac Cells

• Capable of contraction
• Capable of conduction

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Contraction of the Heart

• Cell membrane must be electrically activated
• Depolarization - Positive ions move into cell and
  negative ions move out of cell
• Repolarization negative ions return to inside
  of cell and positive ions move out of cell
• This movement of ions is recorded by EKG

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Cardiac Terminology

Systole Diastole
Electrical Cycle Depolarization Repolarization
Activation Recovery
Excitation Recovery
Mechanical Cycle Contraction Relaxation
Emptying Filling
Shortening Lengthening
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EKG Representation of Heartbeat
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The Normal Electrocardiogram
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Objectives

• Explain how electrical current in the heart is
  generated
• Differentiate between EKG waves, segments,
  intervals, and complexes
• Describe how the movement of electricity through
  the heart produces predictable wave patterns
• Describe the method of detection and recording of
  these wave patterns by the EKG machine

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Detection and Recording

• Transmembrane potential electrical difference
  between the inside and outside of the cell
• Action potential changes that occur during the
  process of depolarization and repolarization
  within a cell as activated by electrical impulse
• Refractory period time during which the cell is
  unable to respond to a stimulus
• Vector path of impulse displaying the direction
  and magnitude of the electrical current

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Normal Heart

• Vector proceeds in same sequence
• Vector is predictable

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EKG machine

• Writing arm
• Recording device (galvanometer)
• Stylus needle responds by heat or pressure
• Lead wires
• Attaches electrodes to machine
• Electrodes
• Provides direct contact with skin

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EKG

• Tracing of electrical voltage produced by
  continual depolarization and repolarization of
  heart
• Shows direction and magnitude of electrical
  current produced by the heart

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Waves

• Deflections from the baseline
• Designated as P, QRS, T

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Waves

• P wave depolarization of atria
• Q wave (may be absent) activation in
  intraventicular septum, first negative deflection
  of QRS
• R wave impulse progression through right and
  left ventricles, first upward deflection of QRS
• S wave completion of left ventricular
  activation
• T wave repolarization of ventricles

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Waves
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Segments

• Straight lines or spaces between waves
• ST segment
• Measured from end of S wave to beginning of T
  wave
• 0.35 to 0.45 seconds
• Isoelectric (flat)

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Segments
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Intervals

• Consists of wave and a connecting straight line
• P-R Interval - measured from onset of P wave to
  beginning of QRS
• Normal 0.12 to 0.20 seconds
• QT Interval - measured from start of Q to end of
  T wave

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Intervals
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Complexes

• Groups of related recorded waves
• QRS complex
• Represents depolarization or contraction of the
  ventricles
• Normal length 0.04 to 0.10

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Complexes
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Explanation of EKG paper
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Measuring Time
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Normal cycle 0.8 seconds
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Heart Rate Calculation 1

• Count the number of large squares between R waves
  and divide into 300

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Heart Rate Calculation 2

• Count number of large blocks between R waves

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Heart Rate Calculation 3

• Count number of small squares between r waves and
  divide that number into 1500
• Most accurate method but can only be used for
  regular rhythms.

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Heart Rate Calculation 4

• Get 6 second strip
• Count number of complete complexes
• Multiply by 10 (6 x 10 60 seconds or 1 minute)
• Special Note Only method that can be used for
  irregular rhythm

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Normal Rhythm Identification

• All P waves appear like all other P waves
• QRS complexes resemble each other
• P-R intervals are constant
• P-P intervals are constant
• R-R intervals are constant
• P before every QRS
• Rate is between 60 to 100 beats per minute

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Normal Sinus Rhythm

• Regular
• P before every QRS, every complex looks the same
• P-R int. 0.20
• QRS 0.10
• Rate approx. 75

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Five Step Method

• Step 1 evaluates the speed of the rhythm to
  determine if it is normal, too slow or too fast.
  A speed between 60-100 maintains the best
  hemodynamic stability. Rates less than 60 or
  greater than 100, can lead to hemodynamic
  instability and become symptomatic.
• Step 2 asks if the rhythm is regular. Rhythms
  originating from the normal pacemakers in the
  heart will be regular. Irregular rhythms indicate
  extra beats or abnormal rhythms.
• Step 3 assesses the shape of the complex. A
  narrow complex is normal. A wide complex
  indicates conduction abnormalities.
• Step 4 asks if a P-wave precedes the QRS complex.
  This represents normal conduction from the atria
  to the ventricles. If the P-wave is absent, the
  impulse is being generated from elsewhere in the
  heart.
• Step 5 assesses whether all the complexes look
  the same. Normal conduction follows the same
  pathway with each beat. Different looking
  complexes indicate the some impulses are
  following alternative or aberrant pathways.

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Abnormal rhythms Sinus Bradycardia

• Less than 60 beats per minutes
• May be normal in athletes
• Other aspects of EKG normal

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Abnormal Rhythms - Tachycardia

• Over 100 beats per minute
• May be caused by exercise or fever
• Other aspects of EKG are normal

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Neat Websites

• http//highered.mcgraw-hill.com/sites/0073520713/s
  tudent_view0/chapter29/ecg_rhythm_exercises1/basic
  _ecg_anatomy/rhythm_strip_quiz_1.html
• http//www.mauvila.com/ECG/ecg.htm
• http//www.ems1.com/columnists/EKG/articles/311340
  -Case-4-The-Pseudo-Normal/

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Lead Systems
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Objectives

• Describe the purpose of an EKG lead
• Differentiate between unipolar and bipolar leads
• Describe the orientation of all 12 leads
• Explain chest and limb lead placement

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Leads

• Each lead views the heart at a unique angle
• Each lead has a positive and a negative pole
  measures the electrical difference between the
  poles

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Limb Leads

• Placed on arms and legs
• Reflect impulses moving in vertical or frontal
  plane
• Six leads I, II, III, AVR, AVL, AVF

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Remember

• Right and left refers to the patients right and
  left

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Limb Lead Placement

• RA right arm between elbow and shoulder
• LA left arm between elbow and shoulder
• RL right leg a few inches above ankle
• LL left leg a few inches above ankle
• Alternate placement for leg leads
• upper legs as close to torso as possible

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Chest Leads

• Demonstrate forces moving anteriorly and
  posterior in a tranverse plane

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Precordial Lead Placement

• V1 right sternal border at 4th intercostal
  space
• V2 left sternal border at 4th intercostal space
• V3 Midway between 2nd and 4th V leads
• V4 5th intercostal space straight down from
  midclavicular notch
• V5 at anterior axillary line at same horizontal
  level as V4
• V6 at midaxillary line on the same horizontal
  level as V4 and V5

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Overview by Lead
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Identifying Rhythms
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Objectives

• Identify normal sinus rhythm.
• Differentiate between various sinus rhythms
• Identify and distinguish each atrial dysrhythmia
• Compare and contrast atrial and ventricular
  dysrhythmias

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Clinical Significance of EKGs

• PCT must recognize abnormal patterns and alert MD

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Sinus Rhythms

• Rhythms beginning in the SA node
• Characteristics
• 11 relationship between P and QRS
• P, QRS, T are in order and consistent in
  configuration
• P-R interval is within 0.12 to 0.20 seconds
• QRS interval is within 0.04 to 0.10
• Heart rate is 60 to 100
• P-R, P-P, R-R intervals are regular

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Terminology Question

• Whats the difference?
• Arrhythmia
• Dysrhythmia

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Dysrhythmias Occur When

• Disturbance in automaticity rate to slow or too
  fast
• Disturbance in conductivity site of impulse
  formation is not in SA node
• Combination of altered automaticity and
  conductivity impulse conduction is abnormal

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Sinus Tachycardia

• Impulse formation faster than normal
• Rate is 100-160 beats per minute
• Faster than normal but not fast enough to
  decrease cardiac output
• Causes exercise, fever, anxiety, hypovolemia
  (decreased fluid volume)
• Same characteristics as Normal Sinus Rhythm
  except rate

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Sinus Bradycardia

• Rate is 30 to 60 beats per minute
• Slow rate can decrease cardiac output
• Can be caused by vomiting, tracheal suctioning,
  valsalva maneuver, drug side effects

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Sinus Arrhythmia

• Impulses originate in SA node but speed up with
  inspiration and slow with expiration
• P-P and R-R intervals vary

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Sinus Arrest or Pause

• Potentially lethal
• SA Node fails
• Beats dropped but bets that do occur appear
  normal
• Sudden decrease in cardiac output can cause
  dizziness, syncope or angina
• Patient may need permanent pacemaker

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Atrial Arrhythmias

• Abnormal electrical activity occurring in the
  atria before the sinus impulse can occur

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Premature Atrial Contractions

• Early firing from ectopic focus in the atria
• Appear earlier than normal in cycle
• Have abnormal P wave and abnormal P-R
• QRS usually normal
• May be caused by alcohol, caffeine, nicotine, low
  potassium, heart or lung disease

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Arial Tachycardia

• Heart rate is 150 to 200
• P wave may be abnormal or hidden in preceding T
  wave
• Decreased cardiac output due to rate and
  increased oxygen demand

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Atrial Fibrillation

• Possibly lethal
• No P waves, P-R cant be measured
• QRS normal but R-R irregular
• Causes underlying heart disease
• May be chronic
• Danger of clots (pulmonary or cerebral) patient
  may be on blood thinner to prevent

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Atrial Flutter

• Ectopic atrial focus takes over - generates
  impulse faster than SA node
• Multiple P waves in sawtooth pattern
• QRS normal
• Atrial rate 250 to 350, regular
• Ventricular rate varies but is regular
• AV node blocks some impulses

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Junctional Rhythms

• Impulses originating from ectopic focus in AV
  node region fire earlier than SA node
• P wave is negative and may occur before, during,
  or after the QRS
• P-R may be shortened or not measurable
• QRS usually normal
• May predispose heart to more serious dysrhythmias

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Junctional Rhythm
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Ventricular Rhythms

• Impulse originates from an ectopic in the bundle
  branches, Purkinje fibers, or ventricular muscle
  before SA node
• Beat caused by this impulse does not produce
  adequate cardiac output
• P wave is absent no P-R interval
• ORS is premature, wide, bizarre
• May be caused by hypoxemia, stress, electrolyte
  imbalance, caffeine, nicotine, alcohol,
  medication toxicity, myocardial infarction
• MAY BE NORMAL FOR PATIENT

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Premature Ventricular Contractions

• Wide, bizarre complex which occurs early
• Example Unifocal

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Premature Ventricular Contractions

• Wide, bizarre complex which occurs early
• Example Multifocal

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Premature Ventricular Contractions

• Wide, bizarre complex which occurs early
• Example Couplet

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Premature Ventricular Contractions

• Wide, bizarre complex which occurs early
• Example Salvo or triplet

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Premature Ventricular Contractions

• Wide, bizarre complex which occurs early
• Example Bigemeny

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Premature Ventricular Contractions

• Wide, bizarre complex which occurs early
• Example Trigeminy

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R-on-T

• Occurs when R of PVC falls on T of preceeding
  beat
• Heart vulnerable to electrical stimulation
• Usually does not produce a sustained ventricular
  dysrhythmia

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Ventricular Tachycardia

• Three ectopic ventricular beats
• Rate 100 to 250 per minute, regular
• Possible lethal arrhythmia
• No P waves, no P-R
• QRS consecutive, wide, bizarre
• Decreased or NO cardiac output
• Will deteriorate into V Fib if not treated

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Ventricular Fibrillation

• CHECK LEADS!!!!!
• Ventricular rhythm is chaotic
• Results from multiple ectopic foci in ventricles
• Ventricles quiver instead of contracting NO
  CARDIAC OUTPUT
• Will deteriorate into asystole

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Agonal

• Wide bizarre complexes from multiple ventricular
  pacemakers

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Asystole

• CHECK LEADS
• No electrical activity

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S-T elevation

• Rhythm - Regular
• Rate - varies
• QRS Duration - Normal
• P Wave - Normal
• S-T Element does not go isoelectric which
  indicates infarction

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A-V Block First Degree

• Caused by a conduction delay through the AV node
  but all electrical signals reach the ventricles
• Rarely causes any problems by itself may be
  seen in athletes
• Rhythm - Regular
• Rate - Normal
• QRS Duration - Normal
• P Wave - Ratio 11
• P Wave rate - Normal
• P-R Interval - Prolonged (gt5 small squares)

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A-V Block Second Degree Type I

• Also called Wenckebach
• Conduction block of some, but not all atrial
  beats getting through to the ventricles
• Progressive lengthening of the PR interval and
  then failure of conduction of an atrial beat,
  this is seen by a dropped QRS complex.
• Rhythm - Regularly irregular
• Rate - Normal or Slow
• QRS Duration - Normal
• P Wave - Ratio 11 for 2,3 or 4 cycles then 10.
• P Wave rate - Normal but faster than QRS rate
• P-R Interval - Progressive lengthening of P-R
  interval until a QRS complex is dropped

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A-V Block Second Degree Type II

• Electrical excitation sometimes fails to pass
  through the A-V node or bundle of His
• Constant P-R interval but not regularly followed
  by ventricular contraction
• Rhythm - Regular
• Rate - Normal or Slow
• QRS Duration - Prolonged
• P Wave - Ratio 21, 31
• P Wave rate - Normal but faster than QRS rate
• P-R Interval - Normal or prolonged but constant

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A-V Block Third Degree

• Atrial contractions are 'normal' but no
  electrical conduction is conveyed to the
  ventricles.
• Ventricles then generate their own signal through
  an 'escape mechanism' from a focus somewhere
  within the ventricle.
• Ventricular escape beats are usually 'slow'
• Rhythm Regular P and Regular QRS but they are
  not related!
• Rate - Slow
• QRS Duration - Prolonged
• P Wave - Unrelated
• P Wave rate - Normal but faster than QRS rate
• P-R Interval - Variation

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Paced Rhythms
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Acquiring the EKG
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Objectives

• Demonstrate correct use of EKG equipment
• Perform simple maintenance and troubleshooting
• Perform accurate, diagnostic EKGs
• Explain effects of patient position
• Understand concept of electrical conduction
  through the skin
• Demonstrate proper skin prep and lead placement
• Recognize artifact and practice artifact
  prevention

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Equipment

• Modern machines are multichannel
• Can transmit EKG via telephone lines
• Machine may store EKGs
• Has 10 lead wires
• Always follow manufacturers directions for use,
  cleaning, storage

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Other considerations

• Drape lead wires over machine do not fold or
  tie
• Inspect lead wires for breaks/frays
• Do not put food or liquids on cart
• Do not put anything on screen
• Be sure machine stays plugged in when not in use
• Store electrodes properly gel can dry out

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Question

• What are beginning actions for any procedure?

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Patient Preparation

• Check physician order or be familiar with
  protocol
• Check patient ID with two identifiers
• Wash hands
• Explain procedure
• Provide privacy

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Patient Position

• Place patient in supine position
• Patient may be at 45 degree angle if short of
  breath
• Have patient uncross legs

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Skin Preparation

• Electrode contact with skin important
• May have to wash dirty/scaly skin
• Epidermis is poor conductor
• Chest hair should be shaved
• Use alcohol to remove skin oils
• Wipe excess perspiration with 4 x 4
• Apply pressure to edges of electrode not center

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Recognizing Artifact

• Extraneous electrical activity
• Can be reduced by having patient touch only the
  mattress not bed rails
• Keep patient quiet and calm
• Keep patient warm
• Position electrodes high on extremities if
  patient has tremor
• Be sure all leads are attached

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Wandering Baseline
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60 cycle interference
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Patient Movement
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BE SURE THAT YOU ARE TREATING THE RHYTHM -

• NOT THE ARTIFACT!

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Special Situations

• Dextrocardia reverse precordial leads
• Large breasts do NOT place electrodes on top of
  breast
• Bilateral breast implants you should apply V4,
  V5, and V6 close to the midaxillary line.
• Note patient abnormalities on EKG
• Do not place electrodes on open wounds, burns,
  or clear dressings
• Do not allow electrodes to touch one another