Transcript Electrocardiogram Interpretation

Electrocardiogram Interpretation
Andrew P. Wilper, MD
Disclosures
Disclaimer
• Brief review presented here today, not
comprehensive
Thanks
• C. Scott Smith, MD
• William Weppner, MD, MPH
• Blaze Sekovski, MD
A bit of history
Nobel Prize
• Willem Einthoven awarded Nobel prize in
1924 for his development of the ECG
Definition
• Electrocardiogram-recording electrical activity
of the heart via electrodes placed on patient
body. Detect heart muscle depolarizations
during each cardiac cycle.
Lead Placement
Leads
• Each lead detects different portions of the
heart anatomy
ECG
• Immeasurably useful for detecting primary
diseases of the heart or cardiac manifestations
of systemic disease
Structure
• Basics of ECG review
• Cases
A Primer
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Have an approach to ECG interpretation!
Rate
Rhythm
Axis
Intervals
Chambers
Ischemia
Rate
• The rate can be estimated by counting the
number of big boxes between QRS complexes
• Rate = 300 / number of large boxes
• You can remember
300…150…100…75…60…50…
• Bradycardia is defined as a HR < 60
• Tachycardia is defined as a HR >100
What is the rate?
What is the rate?
What is the rate?
Number of big
boxes=4
300/4=75
What is the rate?
What is the rate?
What is the rate?
300/~8
Rate=37
A Primer
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Have an approach to ECG interpretation!
Rate
Rhythm
Axis
Intervals
Chambers
Ischemia
Rhythm
• Look for p waves before each QRS complex
• Sinus rhythm has a P wave before every QRS,
and a QRS after every P wave
• Are QRS complexes regular or irregular?
What is the rhythm?
What is the rhythm?
What is the rhythm?
What is the rhythm?
What is the rhythm?
What is the rhythm?
Extra Credit
A Primer
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Have an approach to ECG interpretation!
Rate
Rhythm
Axis
Intervals
Chambers
Ischemia
Axis
• The axis refers to the direction of
depolarization that spreads throughout the
heart
• It can be determined by summating the
vectors in the frontal plane
•A normal axis is between 0 and +90 degrees.
Left Axis=
zero to -90
degrees
Right
Axis= +90
to +150
degrees
Normal Axis=
zero to +90
degrees
Axis
• A quick and easy way to determine axis is to
look at leads I and aVF:
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I
+
+
-
aVF
+
+
-
Axis
Normal
Left axis deviation
Right axis deviation
Extreme Right axis deviation
What is the axis?
What is the axis?
Up in I and aVF
Normal Axis
What is the axis?
What is the axis?
Up in I and
down in aVF
Left Axis
What is the axis?
Down in I and up in aVF
Right axis deviation
Left Axis Deviation
• Left ventricular hypertrophy
• Left bundle branch block
• Left anterior fascicular block
Right Axis Deviation
• Spurious (arm electrode reversal)
• Dextrocardia
• Right ventricular overload
– Acute-PE, severe asthma attack
– Chronic-COPD, pulmonic stenosis, pulmonary htn
• Lateral wall AMI
• Left posterior fascicular block
• RBBB
A Primer
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Have an approach to ECG interpretation!
Rate
Rhythm
Axis
Intervals
Chambers
Ischemia
Intervals
• The Atria
– P wave: Represents the contracting atria
– PR interval: Beginning of the P wave to the
beginning of the QRS complex
– Normal duration .12-.20 seconds or 3-5 small
boxes
– Prolonged PR interval: Heart block
– Shortened PR: Accessory pathways
Intervals
• The Ventricle
• QRS complex: Represents the contracting
ventricle
• QRS duration: Is measured from start of QRS
to end of QRS
• Normal is <.12 seconds or 3 small boxes
• Prolonged QRS seen in ventricular conduction
abnormalities such as LBBB or RBBB
Intervals
• T wave represents repolarization of the
ventricle
• QT interval: Measured from the beginning of
the QRS complex to the end of the T wave
• The QT interval is inversely proportional to the
heart rate
• A rule of thumb the QT interval should be ½
the RR interval for HR’s from 60-80.
A Primer
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Have an approach to ECG interpretation!
Rate
Rhythm
Axis
Intervals
Chambers
Ischemia
RIGHT VENTRICULAR HYPERTROPHY (RVH)
• Right axis deviation without other cause (RBBB, ALMI)
• R wave in V1 > 7mm
• S waves in V5 and V6
RIGHT ATRIAL ENLARGEMENT
(RAE)-Tall narrow P waves
• P wave > 2.5 small boxes high best
seen in inferior leads
RVH ECG
R wave in v1 >7mm
Down in I and up in aVF-Right axis
S waves in V5 and V6
RAE ECG
P wave > 2.5 small boxes high
LEFT ATRIAL ENLARGEMENT (LAE)
• P wave > 2.5 small wide (especially in inferior leads)
• Notched P wave in II
• Negative terminal deflection in P wave in lead V1
LAE ECG
Sinusoidal p wave in V1
Broad P wave in inferior leads
LEFT VENTRICULAR HYPERTROPHY (LVH)
The Cornell criteria for LVH
S in V3 + R in aVL > 28 mm (men)
S in V3 + R in aVL > 20 mm (women)
Most accurate
Sensitivity ~ 50%
Specificity ~ 95-100%
Inspiration
Normal
Paradoxical
Expiration
LVH ECG
Measure S in V3 and R in aVL
A Primer
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Have an approach to ECG interpretation!
Rate
Rhythm
Axis
Intervals
Chambers
Ischemia
Infarction
• Q wave: represents infarction if >1 box by 1
box and in contiguous leads
• ST segment: Elevation during infarction with
typical convex pattern
• Depressed with ischemia
• T wave: May become inverted during
ischemia and/or infarction
ISCHEMIA
• ST elevation (transmural ischemia)
In setting of MI, data suggests that an invasive approach
has better outcomes (may have Printzmetal’s)
Beware of pericarditis, early repolarization, LVH
• ST depression (subendocardial ischemia)
In the setting of MI, this can be treated with anticoagulants
unless hypotensive or not resolving with treatment
Beware hyperventilation, digoxin, CNS disease
• T wave inversion
Beware BBB, LVH w/strain, digoxin, CNS (NL in aVR)
• Q wave
Old transmural scar OR beware accessory pathway
What is the abnormality?
Q waves in antero-lateral
leads suggesting prior
transmural infarction
You are seeing a 61-year-old man in urgent care. He complains of
vague chest pain and dyspnea. Both are worse when lying. He had
a flu like illness earlier in the week.
Pericarditis – Don’t cath
ACUTE PERICARDITIS
 History: Pain is better sitting forward
 Physical exam: Friction rub,  CO, pulses paradoxus
 Findings:
 Diffuse ST elevation and PR depression (except aVR and V1)
 Elevated ESR, CRP
 Causes:
 Infection (viral, bacterial, TB)
 Inflammatory (SLE, other)
 Traumatic
 Treatment: NSAID’s, colchicine. Avoid steroids in recurrent
pericarditis
You are seeing a 61-year-old man in urgent care. He complains of
vague chest pain and dyspnea. EMS says he resisted leaving his
house and he feels he might die.
Panic attack with RBBB – Don’t cath
You are seeing a 61-year-old man in urgent care. He complains of
vague chest pain and dyspnea. The pain is squeezing and radiates
into his jaw and L shoulder.
Anterior STEMI complicated by RBBB and LAFB – CATH!
You are seeing a 61-year-old man in urgent care. He complains of
vague chest pain and dyspnea. The pain is squeezing and radiates
into his jaw and L shoulder.
Inferior-lateral NSTEMI – Cath optional
Break