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Basic Principles of the Cardiovascular System
Patient Care Techncian
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.
Anatomy of the Heart
• 4 chambered pump
• Weighs less than 1 pound
• Size of closed fist
• Located in mediastinum – between lungs, sternum, spine
Chambers
Valves
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?
Where are these valves?
• Tricuspid valve
• Mitral valve
• Pulmonary semilunar valve
• Aortic valve
Chordae tendoneae
Heart Layers
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
Circulation
• Pulmonary
• Systemic
• Coronary
Pulmonary Circulation
Pulmonary Circulation
Systemic Circulation
Coronary Circulation
Coronary Circulation
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.
Question
• Where and when do coronary arteries fill?
Coronary Sinus
Blood Vessels
• Define the following:– Artery– Arteriole– Vein– Venule– Capillary– Aorta– Vena Cava– Pulmonary artery– Pulmonary vein
Question
• What vessels, structures and/or organs are included in each type of circulation?
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.
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.
Conduction Pathways
• Network of conducting tissue
• Specialized cells – do not contract
• Initiates each heartbeat and controls rhythm
Sinoatrial Node
• Located in right atrium
• Main cardiac pacemaker
• Normally generates impulses at rate of 60 to 100 beats per minute
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
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
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
Cardiac Electrical System
Cool Website!
• http://science.howstuffworks.com/environmental/life/human-biology/heart4.htm
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
Two Types of Cardiac Cells
• Capable of contraction
• Capable of conduction
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
Cardiac Terminology
• Systole Diastole
Electrical Cycle Depolarization Repolarization
Activation Recovery
Excitation Recovery
Mechanical Cycle
Contraction Relaxation
Emptying Filling
Shortening Lengthening
EKG Representation of Heartbeat
The Normal Electrocardiogram
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
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
Normal Heart
• Vector proceeds in same sequence
• Vector is predictable
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
EKG
• Tracing of electrical voltage produced by continual depolarization and repolarization of heart
• Shows direction and magnitude of electrical current produced by the heart
Waves
Deflections from the baseline
Designated as: P, QRS, T
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
Waves
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)
Segments
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
Intervals
Complexes
• Groups of related recorded waves
• QRS complex– Represents depolarization or contraction of
the ventricles– Normal length 0.04 to 0.10
Complexes
Explanation of EKG paper
Measuring Time
Normal cycle 0.8 seconds
Heart Rate Calculation #1
• Count the number of large squares between R waves and divide into 300
Heart Rate Calculation #2
• Count number of large blocks between R waves
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.
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
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
Normal Sinus Rhythm
• Regular• P before every QRS, every complex looks the same• P-R int. = 0.20• QRS = 0.10• Rate = approx. 75
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.
Abnormal rhythms – Sinus Bradycardia
• Less than 60 beats per minutes• May be normal in athletes• Other aspects of EKG normal
Abnormal Rhythms - Tachycardia
• Over 100 beats per minute• May be caused by exercise or fever• Other aspects of EKG are normal
Neat Websites
• http://highered.mcgraw-hill.com/sites/0073520713/student_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/
Lead Systems
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
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
Limb Leads
• Placed on arms and legs
• Reflect impulses moving in vertical or frontal plane
• Six leads: I, II, III, AVR, AVL, AVF
Remember
• Right and left refers to the patient’s right and left
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
Chest Leads
• Demonstrate forces moving anteriorly and posterior in a tranverse plane
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
Overview by Lead
Identifying Rhythms
Objectives
• Identify normal sinus rhythm.
• Differentiate between various sinus rhythms
• Identify and distinguish each atrial dysrhythmia
• Compare and contrast atrial and ventricular dysrhythmias
Clinical Significance of EKG’s
• PCT must recognize abnormal patterns and alert MD
Sinus Rhythms
• Rhythms beginning in the SA node• Characteristics
– 1:1 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
Terminology Question
• What’s the difference?– Arrhythmia– Dysrhythmia
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
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
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
Sinus Arrhythmia
• Impulses originate in SA node but speed up with inspiration and slow with expiration
• P-P and R-R intervals vary
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
Atrial Arrhythmias
• Abnormal electrical activity occurring in the atria before the sinus impulse can occur
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
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
Atrial Fibrillation• Possibly lethal • No P waves, P-R can’t 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
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
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
Junctional Rhythm
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
Premature Ventricular Contractions
• Wide, bizarre complex which occurs early• Example: Unifocal
Premature Ventricular Contractions
• Wide, bizarre complex which occurs early• Example: Multifocal
Premature Ventricular Contractions
• Wide, bizarre complex which occurs early• Example: Couplet
Premature Ventricular Contractions
• Wide, bizarre complex which occurs early• Example: Salvo or triplet
Premature Ventricular Contractions
• Wide, bizarre complex which occurs early• Example: Bigemeny
Premature Ventricular Contractions
• Wide, bizarre complex which occurs early• Example: Trigeminy
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
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
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
Agonal
• Wide bizarre complexes from multiple ventricular pacemakers
Asystole
• CHECK LEADS• No electrical activity
S-T elevation• Rhythm - Regular • Rate - varies• QRS Duration - Normal • P Wave - Normal • S-T Element does not go isoelectric which indicates
infarction
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 1:1 • P Wave rate - Normal • P-R Interval - Prolonged (>5 small squares)
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 1:1 for 2,3 or 4 cycles then 1:0. • P Wave rate - Normal but faster than QRS rate • P-R Interval - Progressive lengthening of P-R interval until a QRS complex is dropped
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 2:1, 3:1 • P Wave rate - Normal but faster than QRS rate • P-R Interval - Normal or prolonged but constant
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
Paced Rhythms
Acquiring the EKG
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
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
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
Question
• What are beginning actions for any procedure?
Patient Preparation
• Check physician order or be familiar with protocol
• Check patient ID with two identifiers
• Wash hands
• Explain procedure
• Provide privacy
Patient Position
• Place patient in supine position
• Patient may be at 45 degree angle if short of breath
• Have patient uncross legs
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
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
Wandering Baseline
60 cycle interference
Patient Movement
BE SURE THAT YOU ARE TREATING THE RHYTHM -
NOT THE ARTIFACT!
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