Download EKG Interpretation 2014

EKG Interpretation
Objectives
• Review approach for reading EKGs
• Keep it simple
• Impress preceptors on rounds
Resources
Interpretation
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Rate
Rhythm
Axis
Hypertrophy
Ischemia, Injury, Infarction
Rate
• Count # of large boxes between 2 successive Rwaves:
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1 box = 300 bpm
2 boxes = 150 bpm
3 boxes = 100 bpm
4 boxes = 75 bpm
5 boxes = 60 bpm
6 boxes = 50 bpm
7 boxes = 43 bpm
8 boxes = 37 bpm
Irregular rhythms
• If the R-R Interval is irregular:
• Count the number of QRS complexes in a 10 sec span (that is on
the entire EKG) and multiply it by 6! {or no. of QRS complexes in a
6 sec span multiplied by 10}
Rhythm
• Determine whether sinus or non-sinus
Sinus Rhythm
• Every QRS preceded by P-wave
• P-wave has normal morphology
• Duration <0.12 sec (<3 boxes)
• Height <2.5 mm
• P-wave has normal axis
• Upright in lead II
• Sinus “arrhythmia”
• Rate varies with respiration
Arrhythmias
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Irregular rhythms
Escape rhythms
Premature beats
Tachy-arrhythmias
Heart blocks
Irregular rhythms
• Wandering atrial pacemaker
• P wave shape varies
• Atrial rate <100
• Irregular ventricular rhythm
• Multifocal atrial tachycardia
• Same as above, but rate>100
• Atrial fibrillation / flutter
Escape rhythm
• Junctional escape
• Originates in AV junction
• Narrow QRS (<0.10ms)
• Rate 40-60
• Ventricular escape
• Originates in ventricles
• Wide QRS (not normal depolarization)
• Rate 20-40
Junctional escape
Premature beats
• Irritable focus spontaneously fires a single stimulus
• Atrial (PAC)
• Ventricular (PVC)
Paroxysmal tachycardia
• A very irritable focus suddenly paces rapidly
• Paroxysmal atrial tachycardia
• Paroxysmal junctional tachycardia
• Paroxysmal ventricular tachycardia
• Look for presence/absence of P waves and ventricular
appearance to determine type
Supraventricular tachycardia
• Often can’t tell between PAT and PJT (both originate above
ventricles & produce narrow QRS)
• Rapid PAT can be so rapid that P waves not visible
• Supraventricular tachycardia (SVT) is umbrella term for both
Flutter vs fibrillation
• Flutter caused by single ventricular focus firing rapidly (250350x/min)
• Fibrillation caused by multiple foci firing rapidly (350450x/min)
Atrial flutter & fibrillation
• Atrial flutter
• Atrial fire so rapidly not every impuse triggers
ventricular contraction
• 2:1, 3:1, 4:1 block, etc
• Atrial fibrillation
• Irregularly irregular
Ventricular flutter & fibrillation
• Ventricular flutter has smooth sine-wave appearance
with no jagged waves
• Often degenerates into ventricular fibrillation
Heart blocks
• AV block
• Bundle branch block
AV block
• 1st degree: delay in normal AV conduction
• PR >0.20 sec
• 2nd degree: interruption in normal AV condution
• 3rd degree: complete dissocation in AV conduction
1st degree AV block
• PR >0.20 sec
2nd degree AV block
• Type I (Mobitz I) aka Wenckebach
• PR progressively gets longer with each beat
• QRS complex is dropped
• Cycle repeats
• Type II (Mobitz II)
• PR stays constant, then one beat isn’t conducted
2:1 AV block
• Sometimes hard to tell Wenckebach vs Mobitz II apart if both
have 2:1 conduction (2 P waves then QRS)
• Wenckebach
• Likely if PR interval lengthened and QRS normal
• Mobitz II
• Likely if PR interval normal and QRS widened
3rd degree AV block
• Complete dissocation between atria & ventricles
• Atria fire regularly
• Ventricles contract independently at either junctional escape
(40-60) or ventricular escape (20-40)
• If above AV nodal junction, then junctional escape rhythm
occurs
Bundle branch block
• Wide QRS (<0.12 sec)
• Left
• RR’ in V5 & V6
• Right
• RR’ in V1 & V2
• Incomplete
• QRS 0.10-0.12 sec
Left bundle branch block
Right bundle branch block
Axis
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Measures overall electrical activity of heart
Limb leads (I, aVF) used to quickly determine axis
Lead I: 0 degrees
aVF: +90 degrees
Axis
Lead I
-90
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+
I
If lead I is positive, the
green zone reveals the
area of electrical activity
0
aVF
–
aVF
-90
If aVF is positive, the
red zone reveals the area
of electrical activity
+
I
0
aVF
-90
I
0
aVF
+90
If we superimpose these
onto one another we
find the axis to be
between 0° & +90°
Left axis deviation
• Usually caused by HTN, aortic valvular disease &
cardiomyopathies
• aVF: negative
• Lead I: positive
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Lead I
-90
+
If lead I is positive
then
the blue zone is the
area of electrical
activity
I
0
aVF
+90
_
aVF
-90
If aVF is negative, the
green zone is the
area of electrical
activity
+
I
0
aVF
+90
If we superimpose
these
onto one another we
find the axis to be
between 0° & –90°
-90
I
0
aVF
+90
Right axis deviation
• Usually secondary to enlarged right ventricle or pulmonary
disease
• Pulmonary HTN
• COPD
• Acute pulmonary embolism
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Lead I
-90
+
If lead I is negative the
green zone encompasses
the area of electrical activity
I
180
0
aVF
+90
_
aVF
-90
If aVF is positive, the
red zone reveals the area
of electrical activity
+
I
180
aVF
+90
0
-90
I
180
If we superimpose these
onto one another, we
find the axis to be
between 90° & 180°
aVF
+90
0
Right atrial enlargement
Left atrial enlargement
Left ventricular hypertrophy
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Large S in V1
Large R in V5
S in V1 + R in V5 >35mm = LVH
aVL > 11-13mm = LVH
Right ventricular hypertrophy
• Normally S > R in V1
• Large R in V1 = RVH
• Large R in V1 will get smaller V2V4
Ischemia, Injury, Infarction
• Ischemia
• T wave inversions or ST depression
• Injury
• ST segment elevation
• >1mm in 2 or more contiguous leads
• Infarction
• Q waves
• 1mm wide or 1/3 height of QRS
Ischemia
Injury
Infarction
Location
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Anterior = V1-V4
Inferior = II, III, aVF
Lateral = I, aVL
Posterior = Large R wave, ST depression in V1 or V2
Anterior MI
Inferior MI
Anterolateral
Posterior MI
Tips for rounds
• Review EKG silently (don’t talk though method unless
asked to)
• Ignore interpretation at top of 12-lead
• Intervals usually ok
• Summarize findings
• Rate
• Rhythm
• Axis
• Hypertrophy
• Ischemia, infarction
Example
• This is a normal sinus rhythm, rate 60, normal intervals, no
hypertrophy, no ischemic or infarctive changes
• This is normal sinus rhythm, rate 75, 1st degree AV block, left
ventricular hypertrophy, possible old inferior MI
• This is atrial fibrillation with a rapid ventricular response
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NSR
Rate 80
Normal axis
Normal intervals, no block
• No hypertrophy
• No ischemic or infarctive
changes
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NSR (sinus tachycardia)
Rate 111
Normal axis
Normal intervals
• One premature ventricular
contraction
• No hypertrophy
• No ischemic or infarctive
changes
• NSR, rate 100
• 1st degree AV block
• Normal axis
• Borderline LVH by
voltage
• No ischemic or
infarctive changes
• NSR, rate 100
• LAD
• Normal intervals
• No hypertrophy
• Acute anterior wall MI with
reciprocal ST depression
inferiorly
• NSR, rate ~60
• Normal axis
• Right bundle branch
block
• No hypertrophy
• No ischemic or
infarctive changes
• NSR, rate ~90
• Normal axis
• Normal intervals
• No hypertrophy
• Old inferior wall MI
with ?inferior
ischemia
• Atrial flutter with
variable block
• Normal QRS (no BBB)
• No hypertrophy
• No ischemic or
infarctive changes
• NSR, rate 75
• Left axis deviation
• Left bundle branch
block
• Left ventricular
hypertrophy
• Can’t tell infarction
because of LBBB
repolarization
changes
• Ventricular tachcardia
• Rate ~170
• Don’t really care
about anything else
• Accelerated junctional
• Rate ~80
• Normal axis
• LVH by voltage
• No ischemic or
infarctive changes
Interpretation
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Rate
Rhythm
Axis
Hypertrophy
Ischemia, Injury, Infarction