Transcript ECG Int W06 2401KB Jan 14 2015 08:21:51 AM

Cardiac Basics
EMT-Intermediate Winter 2006
-Basic Anatomy of the Heart
-Electrical Conduction of the Heart
-A System of Defining 3-Lead EKG’s
Heart A & P
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Location
Pieces, Parts
Important Vessels
Electrolyte Role
Pulling apart
waveforms
Valves
&
Vessels
Review of Important Vessels
Electrolytes & Conduction
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“Excitable” cells of the Heart
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Self-depolarizing cells (Automaticity)
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Electrolytes of the Heart (Na+ / K+/ Ca++)
Cardiac Muscle Fibers
Cardiac Muscle
The Components
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SA Node
Internodal Pathways
AV Junction
AV Node
Bundle of His
L & R Bundle Branch
Purkinje Network
Purkinje Fibers
The Route
Impulse Pathways
Ode to a Node
Have a heart, and have no fear,
The SA node is over here.
Beating at a constant rate,
60 – 100 is really great.
The AV node can make a show,
If SA node has gone too slow.
40 – 60 is not too bad
If it’s all you’ve got, you will be glad.
Should the whole thing drop it’s speed,
His and bundle branches will take the lead.
And that, my friend is the whole and part,
Of the conduction system of your heart.
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Flip and See ECG, Cohn/Gilroy-Doohan
Sino Atrial
Node
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The Natural “Pacemaker”
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Connects directly
to atrial fibers
Fires 60-100 times per minute
Wavelike Atrial Depolarization
The P-Wave
0.20 Seconds per 5 Boxes
.04 Sec .04 Sec .04 Sec
.04 Sec
.04 Sec
P-Wave
QWave
P-R Interval
AV Junction
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Receives impulses from SA
Node via the Atrial Cells
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An electrical funnel
Impulses hit at various times
Causes delay
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PR-I
Susceptible to blockage
Path from A to V
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Delivers impulse to the AV
Node
Atrio-Ventricular Node
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Lies between the Atria
and Ventricles
Collects impulses from
above
Stimulates Ventricles
If unstimulated
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Intrinsic rate 40-60
Bundle of His /
Left and Right Bundle Branches
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Distributes Impulses from the Node
“The Ventricular Messengers”
Purkinje Network/Fibers
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Direct connection with ventricular
tissue
Intrinsic rate 20-40 if unstimulated
T-Wave
P-Wave
P-R Interval
QRS
Complex
Another look
A System of Checks & Balances
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Baroreceptors
(Pressoreceptors)
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Found:
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Respond by:
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Internal carotid arteries
Aortic Arch
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Chemoreceptors
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Stimulating sympathetic
Adrenergic response
Alpha, Beta & Dopaminergic
Norepi & Epi release
Inhibiting Parasympathetic
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Acetylcholine
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Found in same places
Monitors pH, O2 & CO2
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Cholinergic Response
Medulla
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Regulatory organ
Electrical Conduction System
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Sympathetic-Thoracic/Lumbar Nerve
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Norepinephrine
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HR,
Contractility
Parasympathetic-Vagus Nerve
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Acetylcholine
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HR (Valsalva)
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Chronotropic-HR
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Inotropic-Contraction
Electrolytes & Conduction
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Membrane Potential (MP)
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Threshold
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Slight difference between charge inside & out
MP becomes high enough to depolarize
Action Potential
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Ability of cells at a given time
Difference (mV) between inside & out
The Cardiac Cycle
Membrane Potential
Sodium-Potassium
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MP Rises
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Na+ Channels Open
Rapid Influx (Fast Channels)
Cell Attains + Charge
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K+ Channels Open
Outflow
The Pump
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ATP Transports:
3 Na+ out & 2 K+ in
Restores Resting cellular
conditions
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Calcium
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Slow Channels
Selective Permeability
“The Wave”
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One cell contraction
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Spreads
Electrical Conduction System
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Na+ in & K+ out = Depolarization
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K+ in & Na+ out = Repolarization
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Imbalances in K+ or Na+
 Effects Automaticity
& Conduction
 Hypo & hyperkalemia affects irritability
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Ca++ - Depolarization and Contraction
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Affects Contractility
Hypo & Hypercalcemia effects contractile force
Phases
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Phase 0 – Rapid Depolarization
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Phase 1 – Early Rapid Repolarization
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Reached max potential -90mV
Fast Na+ Channels Open
Cell now positive +25mV
Fast Na+ Channels Close
K+ still being lost
MP approaching 0mV
Phase 2 – Prolonged Slow Repolarization
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Plateau Phase
Muscle finishing contraction
Beginning to relax
MP staying close to 0mV
Phases
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Phase 3 – End of Rapid Repolarization
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K+ returns to inside
Cell returns to -90mV
Almost ready
Phase 4
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Na+ - K+ Pump turns on
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Sends Na+ out
Brings K+ in
Ready to do it all over again now 
Refractory Periods
Excuse me!!! I hate to interrupt again, but, who cares???
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Absolute Refractory Period
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Relative Refractory Period
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Polarity of cell prohibits depolarization
Cell is returning to ready state for
depolarization
Impulse now is BAD!!!
R on T Phenomenon
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Causes VT & VF
Treated with defibrillation
 Can be caused by:
– Frequent PVC’s
– EMT-P not pushing the “sync”
button
What is an:
EKG?
 ECG?
 EEG?
 EGG?
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Isn’t School Great?
QRS Complex
The Electrocardiograph (ECG, EKG)
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Electrical Activity
– Not Heart Action
Records + and – impulses
Paper runs at 25mm/s
Counting Rates
– 300-150-100-75-7060-50
– 6 second strip x 10
– 10 Second Strip x 6
– The little number on
the monitor 
Lead Considerations
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$25,000 mVoltmeter
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Lead Views:
– Lateral
 2 – Inferior
 3 – Inferior
1
What is going on in there?
The Six Step Approach
What is the Rate?
 Is the Rhythm Regular?
 Are there P-Waves?
 Is the P-R Interval Normal?
 Is the QRS Complex Normal?
 Is There a P-Wave for Every QRS?
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Step 1 = Rate
Is the rate between 60-100 (Sinus)
 Between 40-60 (Junctional/Bradycardic)
 Above 100 (Tachycardic)
 Between 20-40 (Ventricular)
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Step 2 = Regularity
At-a-glance: Does it look regular?
 Are the P-Waves evenly spaced?
 Are the QRS Complexes evenly spaced?
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Step 3 = P-Waves
Are P-Waves present?
 Are they upright and rounded?
 Are they irregular in any way: Notched /
Peaked / Depressed…?
 Are they all the same?
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Step 4 = P-R Interval
Is the P-R Interval between 0.12-0.20?
 Is it too long / too short? (Block)
 Is it the same on every conduction?
 Is it absent?
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Step 5 = QRS Complex
Is it there?
 Is it between 0.04 - 0.12?
 Does it have any abnormalities? (Notched /
Rabbit Eared / Wide / Bizarre)
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Step 6 = P-QRS Married?
Is there a P-wave for every QRS?
 Are there more P-Waves than QRS?
 Are the P-Waves after or within the QRS?
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Describe What You’ve Found!!!
IN GENERAL (underlying rhythms)!!!
 What are the abnormalities?
 Does it originate in the Sinus Node?
 Does it follow through from the Atria to the
ventricles? Are there abnormal delays?
 What are the exceptions to the underlying
rhythm? (Describe those also)
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Normal Sinus Rhythm
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Rate: 60 - 100
Regularity: Very
P-Waves: Present and Normal
P-R I: 0.12-0.20 sec
QRS: 0.04-0.12 sec and Normal
Married: 1 P: 1 QRS, no extras or shortages
Sinus Arrhythmia
Rate: 60 - 100
 Regularity: Irregular
 P-Waves: Present and Normal
 P-R I: 0.12-0.20 sec
 QRS: 0.04-0.12 sec and Normal
 Married: 1 P: 1 QRS, no extras or shortages
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Sinus Tachycardia
Rate: Over 100
 Regularity: Regular
 P-Waves: Present and Normal
 P-R I: 0.12-0.20 sec
 QRS: 0.04-0.12 sec and Normal
 Married: 1 P: 1 QRS, no extras or shortages
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Sinus Bradycardia
Rate: Less than 60
 Regularity: Regular
 P-Waves: Present and Normal
 P-R I: 0.12-0.20 sec
 QRS: 0.04-0.12 sec and Normal
 Married: 1 P: 1 QRS, no extras or shortages
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Atrial Fibrillation
Rate: Usually tachy
 Regularity: Irregular (Irregularly irregular)
 P-Waves: Not Discernible
 P-R I: Undeterminable
 QRS: 0.04-0.12 sec
 Married: Undeterminable
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Atrial Flutter
Rate: Usually tachy
 Regularity: Atria Regular
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Ventricles May be Irregular
P-Waves: Sawtooth Pattern 2:1, 3:1, 4:1...
 P-R I: 0.12-0.20 sec on conducting beat
 QRS: 0.04-0.12 sec
 Married: P-waves outnumber QRS
 (Picket fence)
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(Paroxysmal) Supra Ventricular
 Rate: 140-220
Tach
Regularity: Regular
 P-Waves: Usually falls within the QRS-T
complex (not visible)
 P-R I: Shorter than 0.12, or absent
 QRS: 0.04-0.12 sec and Normal
 Married: Undeterminable
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SVT
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WPW
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Usually based on Hx.
Delta wave on Q
Shortened PR-I
No Verapamil – Accessory Path use increase
1st Degree Heart Block
Rate: 60 - 100
 Regularity: Very
 P-Waves: Present and Normal
 P-R I: Longer than 0.20 sec
 QRS: 0.04-0.12 sec and Normal
 Married: 1 P: 1 QRS, no extras or shortages
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2nd Degree Heart Block (Type 1)
Wenkebach
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Rate: Can be Normal, or usually brady
Regularity: Irregular
P-Waves: Present and Normal
P-R I: Lengthens until beat is dropped
QRS: 0.04-0.12 sec and Normal
Married: P-wave present on conducting beats,
increased delay causes missed QRS
2nd Degree Heart Block (Type 2)
 Rate: Less than 60 Mobitz II
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Regularity: Irregular
P-Waves: Present, 2:1, 3:1, 4:1
P-R I: 0.12-0.20 sec on conducting beat
QRS: 0.04-0.12 sec, may begin to widen
Married: P-wave for every QRS and extras
depending on conduction ratio
3rd Degree Heart Block (CHB)
Complete Heart Block
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Rate: Ventricular Rate 40-60
Regularity: Atria-Regular
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Vent-Regular
P-Waves: Present and Normal
P-R I: Atria independent of Ventricles
QRS: Usually greater than 0.12 sec
Married: P-waves completely unrelated to QRS
Complexes.
Complete Heart Block
Junctional
Rhythm
 Rate: 40-60
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Regularity: Regular
P-Waves: Inverted, Retrograde or Absent
P-R I: Shortened or absent
QRS: 0.04-0.12 sec
Married: P-wave for every QRS, sometimes not
visible
Junctional
Junctional Accelerated Rhythm
Rate: 60-100
 Regularity: Regular
 P-Waves: Inverted, Retrograde or Absent
 P-R I: Shortened or absent
 QRS: 0.04-0.12 sec
 Married: P-wave for every QRS,
sometimes not visible
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Junctional Tachycardia
Rate: 100-140
 Regularity: Regular
 P-Waves: Inverted, Retrograde or Absent
 P-R I: Shortened or absent
 QRS: 0.04-0.12 sec
 Married: P-wave for every QRS,
sometimes not visible
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Ventricular Tachycardia
Rate: 100-220
We’ll look at Torsades de Pointes in Lab
 Regularity: Regular
 P-Waves: None
 P-R I: None
 QRS: Greater than 0.12 sec
 Married: NO
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Ventricular Tachycardia
Ventricular
Fibrillation
 Rate: No ventricular rate
Regularity: Irregular
 P-Waves: No
 P-R I: No
 QRS: No, unorganized ventricular baseline
 Married: No
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Ventricular Fibrillation
Asystole
Rate: 0
 Regularity: N/A
 P-Waves: None
 P-R I: N/A
 QRS: None
 Married: No (verify a second lead)
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Asystole
Agonal / Idioventricular
Rate: 20-40
 Regularity: Irregular
 P-Waves: None
 P-R I: N/A
 QRS: Wider than 0.12 sec
 Married: NO (a dying heart)
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Idioventricular
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Less regular than this!
Exceptions / Disruptions
Premature Ventricular Contractions
 Premature Atrial Contractions
 Bundle Branch Blocks
 Pacer Considerations (Atrial, Ventricular or
Both)
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Premature Ventricular
Contractions
Wide, Bizarre QRS Complex
 Always identify the underlying rhythm first
 Can appear in couplets, triplets, short runs
of V-Tach, bigeminy and trigeminy
 Can be uni-focal or multi-focal
 Caused by random firing within the
ventricles
 Not accompanied by a P-wave
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PVC’s
PAC’s
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P-QRS Complex
appearing in an
unexpected location
Caused by a stimulus
from within the Atria,
but not from the SA
Node
PJC
Bundle Branch Block
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Any rhythm having a BBB will have a
widened twin peaked R-Wave
Paced Rhythms
Patients may have various types of
pacemakers
 Atrial
 Ventricular
 Both
 Vertical spike on monitor is an indicator
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Paced Rhythms Various
Artifact
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60 Cycle Interference
Loose Leads/Moving Ambulance
In Summary
Really Cool Physiology!!!
 GENERAL RULES to Interpretation
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Applicable to 3 – lead monitoring
Practice, Practice, Practice…
 Remember the rules, NOT how it looks
coming from one patient or one rhythm
generator!!!
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Sources – In order of preference
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Many of the pictures and info from:
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Flip and See ECG, 2nd Edition
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Cohn/Gilroy-Doohan
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Paramedic Paramedic Textbook, Revised 2nd Edition
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Mick J. Sanders, Mosby
ECG’s Made Easy, 2nd Edition
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A great resource
Barbara Aehlert, RN, Mosby
Basic Dysrhythmias, Interpretation and Management,
3rd Edition
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Robert J. Huszar, Mosby