Download Understanding the Electrocardiogram

Understanding the
Electrocardiogram
David C. Kasarda M.D. FAAEM
St. Luke’s Hospital, Bethlehem
Overview
1.
2.
3.
4.
5.
6.
Hypertrophy
AV Conduction Abnormalities
IV Conduction Abnormalities
Ischemia/Infarction
Disease Patterns
End
Hypertrophy
Thickening of the heart muscle
Multiple causes
INCREASED WORKLOAD
Right Atrial: Pulmonary HTN, COPD
Left Atrial: Mitral Insufficency
Right Ventricular: Lung disease, congenital heart
disease
Left Ventricular: HTN, Aortic Stenosis
Right Atrial Hypertrophy
The electrical forces generated by atrial
depolarization are directed septally and
inferiorly
V1 is the best lead to view the atria as it overlies
the atria (Right, 4th parasternal space)
Wave is usually DIPHASIC
Initial deflection LARGER than second deflection
Right Atrial Hypertrophy
Inferior Leads (II, III, aVF)
Tall P waves > 2.5 mm in height
Left Atrial Hypertrophy
The electrical forces generated by atrial
depolarization are directed septally and
inferiorly
V1 is the best lead to view the atria as it overlies
the atria (Right, 4th parasternal space)
Wave is usually DIPHASIC
Second deflection LARGER and NEGATIVE than initial
deflection
Left Atrial Hypertrophy
Inferior Leads (Specifically Lead II)
Notched P wave
Duration > 0.12 sec
Right Ventricular Hypertrophy
RECALL
Anatomically, the right ventricle makes up most
of the ANTERIOR and INFERIOR boarders of
small r
the heart
The right ventricle has LESS MUSCLE MASS
than the left ventricle
Ventricular depolarization proceeds LEFTWARD
and POSTERIORLY (thicker part of left ventricle
is posterior)
DEEP S
Right Ventricular Hypertrophy
Criteria
Large (Dominant) R wave in V1
R wave gets progressively SMALLER from V1 to
V2 to V3 to V4
Deep S wave in V6
Right Axis Deviation
V1
> 110 degress
Right atrial enlargement typically seen
Left Ventricular Hypertrophy
As Left Ventricle becomes larger
The QRS voltage INCREASES
ESPECIALLY in the PRECORDIAL LEADS
Deep S wave in V1
There is often ST DEPRESSION in V5 and V6
“Strain pattern”
Left Ventricular Hypertrophy
Diagnostic Criteria
Sokolow-Lyon Criteria (voltage criteria)
S in V1 or V2 + R in V5 or V6 > 35mm = LVH
Other Criteria
aVL > 12mm
Overview
1.
2.
3.
4.
5.
6.
Hypertrophy
AV Conduction Abnormalities
IV Conduction Abnormalities
Ischemia/Infarction
Disease Patterns
End
A-V Conduction
Conduction between the atria and
ventricles is disturbed
Increased PR interval
Dropped QRS Complex
Atrial electrical activity WITHOUT ventricular
electrical activity
Complete dissociation of atrial and ventricular
electrical activity
First Degree Heart Block
Prolongation of the PR interval
> 0.2 seconds
5 small boxes or 1 large box
No dropped QRS complexes
Benign
Second Degree Heart Block
Not all P waves have following QRS
complexes
Beat “drop outs” occur
Three Types
Mobitz Type I (Wenckebach)
Mobitz Type II
High Grade AV Block
Mobitz Type I
PR interval gets PROGRESSIVELY
LONGER until there is a DROPPED QRS
COMPLEX
The PR interval that follows the dropped
beat is THE SHORTEST
The block DECREASES with exercise
DROPPED
4:3 block becomes a 6:5 block
Benign
Mobitz Type II
Beats are dropped IRREGULARLY without
PR interval prolongation
PR interval and R-R interval are CONSTANT
between conducted beats
Class I indication for pacemaker
DROPPED
High AV Block
Two or more P waves not followed by a
QRS complex
NOT COMPLETE BLOCK
P waves that conduct QRS complexes are at
FIXED INTERVALS
Class I indication for pacemaker
Third Degree (Complete) Heartblock
Total Block
NO ATRIOVENTRICULAR CONDUCTION
P waves and QRS complexes have no temporal
relationship
Complete
Heart Block for pacemaker
Class
I indication
High Grade AV Block
Intraventricular Conduction
Abnormalities
Unifascicular Blocks
Bifascicular Blocks
Right Bundle Branch Block
Left Anterior Fascicular Block
Left Posterior Fascicular Block
Left Bundle Branch Block
RBBB + LAFB
RBBB+ LPFB
Trifascicular Blocks
Right Bundle Branch Block
Found in patients with and without
structural heart disease
Criteria
QRS duration > 0.12 sec
rSR’ pattern in V1
Deep S wave in Lead I and V6
Left Anterior Fascicular Block
Found in patients with and without structural heart
disease
No prognostic significance
Although commonly seen after acute anterior wall MI
Criteria
QRS generally < 0.12 sec
Left axis (-45 to -90 degrees)
rS pattern in leads II, aVF, and III (S > r)
qR pattern in leads I and aVL
Left Posterior Fascicular Block
Much less common than LAFB
Finding is nonspecific
Criteria
QRS duration < 0.12 sec
Right axis
rS pattern in leads I, aVL
qR pattern in lead III, and often aVF
Intraventricular Conduction
Abnormalities
Unifascicular Blocks
Bifascicular Blocks
Right Bundle Branch Block
Left Anterior Fascicular Block
Left Posterior Fascicular Block
Left Bundle Branch Block
RBBB + LAFB
RBBB+ LPFB
Trifascicular Blocks
Left Bundle Branch Block
Causes: CAD, HTN, Cardiomyopathy, Pacer
Criteria
QRS duration > 0.12 seconds
Broad R wave in leads I, V5, V6
No Q wave in V6
QS or rS complex in lead V1
RBBB with LAFB
MOST COMMON TYPE
Criteria
QRS duration > 0.12 seconds
rsR’ or qR in leads V1 and V2
Wide or deep S waves in leads I and V6
Left axis
LAFB criteria
rS pattern in leads II, aVF, and III (S > r)
qR pattern in leads I and aVL
RBBB with LPFB
Much less common
Criteria
QRS duration > 0.12 seconds
rSR’ or rR’ in lead V1
Deep or wide S wave in V6
Right axis
LPFB Criteria
rS pattern in leads I, aVL
qR pattern in lead III
Intraventricular Conduction
Abnormalities
Unifascicular Blocks
Bifascicular Blocks
Right Bundle Branch Block
Left Anterior Fascicular Block
Left Posterior Fascicular Block
Left Bundle Branch Block
RBBB + LAFB
RBBB+ LPFB
Trifascicular Blocks
1st degree AV Block
RBBB
Trifascicular Block
LAFB
May progress to complete heart block and
sudden death
Criteria
1st degree heart block (PR > 0.2 seconds)
RBBB
Either LAFB or LPFB
Overview
1.
2.
3.
4.
5.
6.
Hypertrophy
AV Conduction Abnormalities
IV Conduction Abnormalities
Ischemia/Infarction
Disease Patterns
End
Analyzing for Ischemia/Infarction
ST segment
Normal
ST segment lies at level of baseline
Analyzing for Ischemia/Infarction
ST Segment Depresion
ST segment lies below the baseline
Indicates myocardial injury that DOES NOT
extend through the entire muscle wall
Analyzing for Ischemia/Infarction
ST Segment Elevation
ST segment lies above the baseline
Indicates FULL THICKNESS muscle wall injury
1 mm of elevation in two contiguous ECG leads
is considered significant
Q waves
Q waves are the FIRST downward
deflection of the QRS complex
Significant Q waves are at least 1/3 the
height of the QRS complex and one or
more small boxes wide
Occur in the presence of full thickness
myocardial necrosis (STEMI)
Infarct Locations
Overview
1.
2.
3.
4.
5.
6.
Hypertrophy
AV Conduction Abnormalities
IV Conduction Abnormalities
Ischemia/Infarction
Disease Patterns
End
Acute Anterior Wall MI
ST elevation
V1-V6
Maximum elevation in V3
Reciprocal depression in the inferior leads
Maximal depression in lead III
Acute Inferior Wall MI
ST elevation
II, III, aVF
Reciprocal ST depression
I, aVL
Acute Lateral Wall MI
ST elevation
I, aVL
V5, V6
Posterior Wall MI
V9
V8
No leads on the standard
ECG have their
POSITIVE electrodes oriented over the
V8
POSTERIOR WALL of the myocardium
THEREFORE
No leads show ST ELEVATION in the case of a
POSTERIOR WALL MI
V9
RECALL
the PRECORDIAL LEADS
Overview
1.
2.
3.
4.
5.
6.
Hypertrophy
AV Conduction Abnormalities
IV Conduction Abnormalities
Ischemia/Infarction
Disease Patterns
End