Transcript conduction-sinus-atrial

Basic ECG
Objectives



Identify the functions of the electrical
conduction system of the heart.
Demonstrate accurate ECG rhythm
interpretation.
Identify key characteristics of normal
and abnormal rhythms.
Sinoatrial Node
(SA Node)
Located in RA near SVC
 Normal pacemaker of heart
 Initiates an impulse
 Intrinsic rate of 60-100

Intra-Atrial Pathways
Located in atrial tissue between SA & AV
nodes
 Conducts impulse from SA  atrial
musculature  AV node
 Anterior, middle, and posterior tracts

Atrioventricular Node
(AV Node)
Located near tricuspid valve
 Delays impulse from atria
 Allows for ventricular filling
 Protective mechanism against rapid
supraventricular impulses

Junctional Tissue
Tissue in lower AV node
 Back-up pacemaker
 Intrinsic rate of 40-60

Bundle of His & R & L Bundle
Branches

Bundle of His connects AV node to
Right & Left bundle branches
R
bundle carries impulse to RV
 L bundle carries impulse to LV
Ventricular Tissue
 Back-up
pacemaker
 Intrinsic rate 20-40
Purkinje System
Distal to the bundle branches
 Rapidly conducts impulses to
ventricular subendocardial layers

ECG Paper

Horizontal axis represents time
 small
box = 0.04 seconds
 5 small boxes = 1 large block = 0.20
seconds
 5 large boxes = 1 second
 Normal strip = 30 large boxes = 6
seconds
ECG Paper cont...

Vertical axis measures:
 amplitude
in millimeters (mm)
 electrical voltage in millivolts (mV)
 1 small block = 1 mm or 0.1 mV
 1 large block = 5 mm or 0.5 mV
Terminology

Depolarization
– The electrical activation of a cardiac cell

Repolarization
Electrical recovery of the cardiac cell
The P Wave
Atrial depolarization
 Characteristics:

 precedes the QRS



2-3 mm high
0.06-0.12 seconds
round & upright
QRS Complex
Ventricular
depolarization
 Characteristics:



follows PR interval
< 0.12 seconds
T Wave

Ventricular
repolarization

Characteristics:


follows S wave
round & smooth
PR Interval
Atrial impulse to the
AV node-bundle of
His-R & L bundles
 Characteristics:

 beginning of P wave to

beginning of QRS complex
0.12-0.20 seconds
ST Segment
Early Ventricular
Repolarization
 Characteristics:


from end of QRS
complex to beginning
of T wave
QT Interval
Ventricular
depolarization &
repolarization
 Characteristics:



beginning of QRS to
end of T wave
0.35 to 0.45 seconds
Monitoring
 Five
leads
Electrodes & Leads
Electrodes measure the direction of
electrical current
 The current is transformed into
waveforms
 The ECG records the waveform
information from different views &
leads

Leads

Provide different views of the heart’s
electrical activity
 Lead



view between a + pole & a - pole
the axis refers to the direction of the current moving
through the heart
direction of the waveform on the ECG
Lead Selection

Based on patient history
Calculation of Heart Rates

R-R….. SMALL BOXES….. DIVIDE into 1500
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6 SECOND METHOD
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RATE CHART
Determine the Rate
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1,500 method
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use with regular rhythms, most accurate
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1,500 small squares = 1 minute
count small squares between 2 consecutive P waves
divide into 1,500 to get atrial rate (1500/30 = 50 bpm)
count small squares between 2 consecutive R waves
divide into 1,500 to get ventricular rate
Determine the Rate cont..
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6 Second method

good method if rhythm is irregular
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use a 6 second strip
count the number of P waves for the atrial rate and multiply
by 10
count the number of R waves for the ventricular rate and
multiply by 10
Determine the Rate cont...
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Sequence method-memorization of:
300-150-100-75-60-50-43
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for atrial rate, locate a P wave on a heavy black line
assign the next heavy black line 300 & begin counting
backwards until you reach the next P wave

for ventricular rate, repeat the same sequence

ECG - HOW TO READ IT?
CHECK THE ATRIAL and VENTRICULAR RHYTHM
Is it REGULAR OR IRREGULAR?
CALCULATE THE ATRIAL AND VENTRICULAR RATE
Same or different?
LOOK FOR P, Q, R, S, AND T
Is there a P wave for every QRS?
Is there a QRS for every P?
PR Interval? QRS width?
FIND THE ORIGIN
Sinus, Atrial, Junctional, or Ventricular?
KNOW THE MECHANISM
Fast, slow, premature, late, fib, flutter or blocked, paced
Measure the PR Interval
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Is the duration 0.12-0.20 seconds?
Is the interval consistent?
Measure the Duration of
the QRS Complex
Is the duration < 0.12 seconds?
 Are all of the complexes the same
size & shape?
 Is there a QRS after each P wave?

Checkpoint
1.
The ECG provides information about:
a.
b.
c.
d.
the contractility of the heart
the electrical activity of the heart
cardiac output and resistance
all of the above
2.
In the electrocardiogram, the QRS represents:
a. ventricular contraction
b. atrial contraction
c. ventricular depolarization
d. discharge of impulse from the sinus node
3.
Indicate the intrinsic rate of the following:
Sinus node
Junctional tissue
_______
Ventricular tissue
Sinus Rhythms
Normal Sinus Rhythms (NSR)
 Sinus Tachycardia (ST)
 Sinus Bradycardia (SB)
 Sinus Dysrhythmia (SD)
 Sinus Pause (Sinus Arrest)

Normal Sinus Rhythm
The SA node (normal Pacemaker) of the heart is in
control
Rhythm: Regular
Rate: 60-100/min
P Wave Precedes each QRS, normal.
PR: 0.12-0.20Sec
QRS: < 0.12 sec & Constant
Sinus Tachycardia
SA node fires faster than 100/min
Rhythm: Regular
Rate: 100-160/min
P Wave: Normal, precedes each QRS
PR: 0.12 - 0.20 sec QRS: <0.12 sec
Sinus Tachycardia
Causes:
* Anemia, Hypoxia, Hypovolemia, Hypotension
* Exercise, Emotion, Anxiety, Pain
* Fever
* Drug related-Caffeine, Epinephrine, Cocaine
* Early sign of CHF
* Theophylline toxicity
* Hyperthyroidism
Management:
* Assess for cause & treat it
* Beta Blockers for primary tachycardia
Sinus Bradycardia
SA Node fires slower than 60/min
Rhythm: Regular
Rate: < 60/min
P Wave: normal, precedes each QRS
PR: 0.12 - 0.20 sec
QRS: < 0.12 sec
Sinus Bradycardia
Causes
Significance

If severe or prolonged,
may cause decrease in
cardiac output and syncope

At risk for escape rhythm
and or premature beats to
gain control due to long
pauses




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Normal in healthy, young,
athletes
Vagal stimulation… MI,
Vomiting, Straining at
stool, Pharyngeal suctioning
Drug effect… Beta blockers
Increased ICP
Hypokalemia
Sick Sinus syndrome
Sinus Bradycardia
Interventions
Assess patient
Hold digoxin, if digoxin toxicity
Relieve source of vagal stimulation, if possible
(treat nausea, shorten periods of
suctioning, no valsalvas)
May need to adjust drug regimen
If symptomatic, treat with Atropine
May require temporary pacemaker
Sinus Dysrhythmia
(Sinus Arrhythmia)
Irregular heart rate; Sinus node in charge;
usually varies with respiratory cycle
Rhythm : Irregular
Rate : 60 - 100
P wave : Normal
PR : Normal
QRS: Normal
The longest R-R interval - the shortest R-R interval
= > 0.12 seconds
Sinus Dysrhythmia
Significance:
Usually none
Causes:
Common in children & outgrown in teens
Variation of Sinus rhythm
Vagal stimulation
Treatment:
Usually none
R/O more serious irregular rhythm
Minimize vagal stimulation
Sinus Pause (Arrest)
Sinus node fails to generate an impulse for one or
more beats; usually reset by sinus node but
escape beats/rhythms may occur
Rhythm: Regular except for pause
Rate: depends on underlying rhythm
No P wave preceding pause
PR: normal
QRS: normal
Sinus Pause
CAUSES
 May decrease
CO
 Duration of
pause
determines
the
seriousness
of
dysrhythmia
SIGNIFICANCE
Vagal stimulation
Sick Sinus
syndrome
Dig. Toxicity
Beta blockers
Ca channel
blockers
Ischemia of SA
node
Pericarditis
Hyperkalema
Amiodarone
INTERVENTIONS
Treat cause
Atropine for
acute
bradycardia
If asleep, wake
the patient
Pause over 3
seconds…
Evaluation
for a pacemaker
(External or
permanent)
Checkpoint
True or False
1.
Sinus dysrhythmia is dangerous and requires immediate
intervention.
2.
The treatment of choice for sinus tachycardia is related to the
cause.
3.
Sinus dysrhythmia is characterized by a slowing and speeding of
the rate.
4.
The first nursing action in relation to a rhythm disturbance is to
check the patient and assess level of consciousness.
Atrial Rhythms
Premature Atrial Complex (PAC)
 Supraventricular Tachycardia (SVT)
 Atrial Flutter
 Atrial Fibrillation

Premature Atrial Complexes
Originates outside the SA node
 Single or multiple ectopic focus
 Various shapes of P waves
 PR - normal; QRS - normal

PACs
Significance
Cause
Interventions
Usually not serious
Common
In pts. with heart
disease… more serious
Emotional stress
Infrequent … No
treatment
In MI … early sign of
CHF
Alcohol, caffeine,
tobacco
Electrolyte imbalance
Hypoxia
Digoxin toxicity
Hyperthyroidism
CV disease
Drugs
Eliminate cause
Drugs
SVT
ABSOLUTELY REGULAR RHYTHM !
USUALLY OCCURS SUDDENLY
RATE: 160-240/min
P WAVE: MAY NOT BE SEEN
PR : NOT MEASURABLE
QRS: NORMAL
Significance - SVT
•If rapid, can decrease cardiac output
•Can cause
•anxiety
•angina
•palpitations
•shortness of breath
•decreased level of consciousness
•decreased BP
•shock
•pulmonary congestion
•CHF
•acute MI
Causes - SVT
NORMAL
CARDIAC
Caffeine
Recreational drugs
Electrolyte imbalance
Hypoxia
Physical & psychological
Stress
MI
Cardiomyopathy
WPW syndrome
Sick-Sinus syndrome
OTHER
Corpulmonale (COPD)
Hyperthyroidism
Dig. Toxicity
INTERVENTIONS
Check Digoxin Level
Valsalva Maneuver
Carotid sinus massage – physicians only
Drugs – Adenosine (drug of choice)
Drugs – Verapamil, Diltiazem,
Oxygen; check ABG if needed
Cardioversion
Patient education – stress management
Carotid Massage
By MDs only!
Both diagnose & terminate PSVT
Auscultate first for bruit
Never compress
both carotids
simultaneously!
Cardioversion
Synchronized cardioversion delivers electrical
stimulus during depolarization - depolarizes all
cells simultaneously, allowing SA node to resume
the pacemaker role
QRS complex must be present
Usually elective
Potassium, digoxin level,emergency equipment,O2,
NPO, IV, TEE, Sedation
Supraventricular Tachycardia
vs.
Sinus Tachycardia
SVT
ST
 Begins abruptly with a
single PAC or PJC.
 Begins more slowly in
response to a physiologic
need.
 Rate: 160 –240
 Rate usually does not
exceed 160.
 Can be terminated with a
vagal maneuver.
 Unaffected or only
momentarily slowed down
by a vagal maneuver
Atrial Flutter
Atrial rate of 250 - 350 beats / min
 Originating from a single ectopic focus
 Saw toothed F waves
 AV node delays the impulses at various
ratios

Atrial Flutter
CAUSE
SIGNIFICANCE
Conditions that enlarge
atrium and elevate atrial
pressures
- mitral valve disease
- hyperthyroidism
- primary myocardial
disease
- pericardial disease
- peripheral & apical
pulses are normal
Seen in pts with MI,
COPD, & hypoxia
- Take a second look at
sinus tachycardia >
150/mt – may be 2:1
conduction!
Occasionally Digoxin
toxicity
Rare in healthy people
- s/s low cardiac out put if
ventricular rate is high
(loss of atrial kick)
- Less stable than A.Fib
- More clinical attention
needed in pts with
ischemic heart disease
INTERVENTION
- Assess the pt.
- Carotid massage by
MD only (temporary)
- Cardioversion
- Drug therapy –
Digoxin, Verapamil,
Ibutilide, Diltiazem,
beta blockers
- Anticoagulation
Atrial Fibrillation
Chaotic, asynchronous electrical activity of atrial
tissue
Irregularly irregular rhythm
Rate - 400/min or more
No distinct P waves - wavy deflection - f waves
No PR interval
QRS - normal: ventricular response can be rapid,
controlled or slow
Radial & Apical pulse rates may vary
Significance of Atrial Fibrillation
Symptoms
Palpitation, Pulse deficit, Irregular pulse
Hemodynamic compromise
Loss of atrial kick ; less ventricular filling
Low CO - hypotension, syncope, low output
S/S heart failure
Increased risk of thromboembolism
Atrial Fibrillation-Causes
Hypertension
Valvular heart disease
Hyperthyroidism
CAD
Acute MI
Pericarditis
Hypoxia
ASD
A FIB – Interventions


Control ventricular response
Anticoagulation to prevent embolus
return to sinus rhythm
Acute
– Medications
 Beta Blockers
 Ca Channel Blockers
– Cardioversion
– Anti-coagulation
Subacute
– Treat Reversible Causes
– Cardioversion
– Anticoagulation

Chronic
– Medications
– Anticoagulation
– Ablation
Checkpoint
1.
Vagal stimulation which may alter the atrial rhythm includes
which of the following:
a.
b.
c.
d.
2.
Rapid breathing
Lying down
Carotid Sinus Massage
Valsalva Maneuver
Atrial fibrillation decreases cardiac output by which of the
following:
a.
b.
c.
d.
Decreasing filling time
Loss of atrial kick
Slowing ventricular rate
Causing Palpitations.
Atrial Arrhythmias
Exercise #1
Atrial Arrhythmias
Exercise #2
Atrial Arrhythmias
EXERCISE #3
Atrial Arrhythmias
EXERCISE #4
Atrial Arrhythmia
Exercise #5
Atrial Arrhythmia
Exercise #6