Ecg as an aid for diagnoses

ECG as an aid for
diagnoses
Prof. Dr. Saad S Al Ani
Senior Pediatric Consultant
Head of Pediatric Department
Sharjah , UAE
saadsalani@aol.com

Nomenclature of electrocardiogram (ECG)
waves and intervals
6/14/2014
ECG as an aid for diagnoses
2
http://www.davita-shop.co.uk/ecg-instruments.html

Important intervals
 Indicates the time between atrial and ventricular
depolarization
PR interval
Normal duration is 3 -5 small squares (120 -200
ms), because a “small square” is defined as 40 ms)
 It is a reflection of mostly AV node conduction
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PR interval (cont.)
 A PR interval longer than200 ms (1big square) in
teens and adults, is the definition of 1◦ AV block
 Intervals shorter than 120 ms (3 small squares) in
teens and adults may indicate:
1. Wolff-Parkinson-White (WPW)
(Short interval with delta wave)
2. Junctional rhythm (with retrograde P wave)
3. Left atrial overload (Widened P wave)
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QRS duration
 Is usually < 100 ms ( ½ a big square)
 QRS >120 ms may be caused by:
1. Bundle branch block (BBB)(right or left)
2. Ectopic ventricular beat (PVC)
3. Ventricular rhythm
4. Ventricular pacemaker
5. Drugs that prolong conduction (e.g. tricyclics)
6. WPW
7. Electrolyte problems (Hyperkalemia)
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QT- interval
 Varies with heart rate
The corrected QT interval (QTc) for heart rate is
normally 340 -440 ms
 With prolonged QTc there is a tendency to
develop:
1. Recurrent syncope
2. Sudden death
3. Torsades de pointes
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QT- interval (cont.)
Causes of Prolonged QTc:
 Genetic or congenital prolonged QT syndrome
( in a child without medications)
 Long QT + sensorineural deafness
(Jervell and Lange-Nielsen syndrome)
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QT- interval(cont.)
Other etiologies for prolonged QT interval include:
Tricyclic overdose
(especially in adolescent)
Hypocalcemia
Hypomagnesemia
Hypokalemia
TH3
• Type Ia and III antiarrhythmics
(Ia = quinidine ,procainamide;
III= Amiodarone, sotalol)
• Starvation with electrolyte
abnormalities
• CNS insult
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QT- interval(cont.)
Short QTc may be caused by:
1. Hypercalcemia
2. Digitalis
3. Congenital
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• Originating in sinus node (SA)
• Result from the depolarization of the atrium
• Normal P wave
· 2mm in height
· <120 ms (3small squares ) in duration
· The axis is 0 -+90◦
Waveforms and segments
P wave
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 Most information from P wave can be derived
from lead II , aVR and V1
 The normal P wave is:
 Positive in lead I , II and aVF
 Positive or biphasic in V1
 Negative in aVR
P wave (cont.)
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A retrograde P wave
 Originating outside the SA node
 Is negative in II (and II and aVF)
 Is positive in aVR
 Indicating an ectopic focus originating in :
1. Inferior part of the atrium
2. The AV junction (often results in short PR interval)
P wave (cont.)
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Right atrial preponderance:
(Enlargement , hypertrophy ,overload)
· The P wave width stays normal(<120 ms)
· Peaking of P wave in lead II and V1
P wave (cont.)
Left atrial overload:
· Widened ,notched ”M” shaped P wave in lead II
Decreased P waves amplitude is seen in severe Hyperkalemia
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T wave
Typically positive in V1 at birth → age 7 days then
inverted
They may be either inverted or upright in V1 during
teen years
Should remain inverted in V1 until ages 9 -10 years
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T wave (cont.)
If T wave remain positive after 7 days and up to
10 years of age in V1 ,this may indicate right
ventricular hypertrophy
Peaked T waves can occur with:
· Hyperkalemia
· Intracerebral hemorrhage
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U wave
Usually small occurs just after T wave
Is mainly something to look at in older
adolescents or adults
Best seen in V2 –V3
Usually a < 1 mm, rounded deflection in the
same direction of T wave
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U wave (cont.)
Prominent U wave
· An increased tendency for torsades de pointes
· It is seen with:
· Hypokalemia
· Bradycardia
· Digitalis
· Amiodarone
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ST -Segment
There are 3 main causes of ST segment elevation:
1. Acute MI
2. Prinzmental angina
3. Pericarditis
· The first 2 are almost never seen in children
Pericarditis is the most common cause of cardiac
chest pain in pediatrics and it affects the whole
heart ,so ST changes should be seen in most leads
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ST –Segment (cont.)
ST segment elevation may also seen in:
· Early repolarization variant
· Intracerebral hemorrhage
· Hypertrophic Cardiomyopathy
· LVH
· LBBB
· Cocaine abuse
· Myocarditis
· Hypothermia
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ST –Segment (cont.)
ST segment depression occurs in pediatrics with:
· Subendocardial ischemia
(especially if down –sloping or
flat)
· LVH with strain
( ST depression with flipped T
wave in left precordial leads)
· RVH (cause RAD,ST
segment depression
preceding a flipped T
wave in V1)
· Digitalis effect
· Hypokalemia
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QRS complex
1.QRS complex:
The mean vector of depolarization of the interventricular
septum points from patient’s left to right, across septum
Depolarization of the ventricles occurs simultaneously
after the depolarization of the interventricular septum
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QRS complex (cont.)
2.QRS complex:
A septal Q wave in V6 generally means normal initial
depolarization
A small ,initial deflection, which is positive in V1 (R
wave) and negative in V6 (Q wave )
The mean QRS vector is strongly to the patient’s left
so a large negative deflection in V1 and positive
deflection in V6
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QRS complex (cont.)
3.QRS complex:
The normal duration of the QRS is < 120 ms
On the frontal plane ,the mean vector is -30 to +100
degree
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Features of
the normal rhythms
and
abnormal rhythms
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Normal Sinus Rhythm
Rhythm - Regular
Rate - (60-100 bpm)
QRS Duration - Normal
P Wave - Visible before each QRS complex
P-R Interval - Normal (<5 small Squares. Anything above
and this would be 1st degree block)
Indicates that the electrical signal is generated by the sinus
node and travelling in a normal fashion in the heart
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Sinus Bradycardia
Rhythm - Regular
Rate - less than 60 beats per minute
P-R Interval - Normal
Usually benign and often caused by patients on beta blockers
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Sinus Tachycardia
Rhythm - Regular
Rate - More than 100 beats per minute
The impulse generating the heart beats are normal,
They are occurring at a faster pace than normal.
Seen during exercise
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Atrial Tachycardia (Physiology)
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http://www.zuniv.net/physiology/book/chapter11.html

Supraventricular Tachycardia (SVT)
Rhythm - Regular
Rate - 140-220 beats per minute
QRS Duration - Usually normal
P Wave - Often buried in preceding T wave
P-R Interval - Depends on site of supraventricular pacemaker
Impulses stimulating the heart are not being generated by the
sinus node, but instead are coming from a collection of tissue
around and involving the atrioventricular (AV) node
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Atrial Fibrillation
Rhythm - Irregularly irregular
Rate - usually 100-160 beats per minute but slower if on
medication
P Wave - Not distinguishable as the atria are firing off all
over
P-R Interval - Not measurable
The atria fire electrical impulses in an irregular fashion
causing irregular heart rhythm
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Atrial Fibrillation (Physiology)
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Atrial Flutter
Rhythm - Regular
Rate - Around 110 beats per minute
P Wave - Replaced with multiple F (flutter) waves, usually
at a ratio of 2:1 (2F - 1QRS) but sometimes 3:1
P Wave rate - 300 beats per minute
P-R Interval - Not measurable
As with SVT the abnormal tissue generating the rapid heart
rate is also in the atria, however, the atrioventricular.
Node is not involved in this case.
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Atrial Ectopic Beat (Physiology)
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1st Degree AV Block
Rhythm - Regular
Rate - Normal
P Wave - Ratio 1:1
P Wave rate - Normal
P-R Interval - Prolonged (>5 small squares)
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2nd Degree Block Type 1 (Wenckebach)
Rhythm - Regularly irregular
Rate - Normal or Slow
P Wave - Ratio 1:1 for 2, 3 or 4 cycles then 1:0
P Wave rate - Normal but faster than QRS rate
P-R Interval - Progressive lengthening of P-R interval
until a QRS complex is dropped
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2nd Degree Block Type 2
Rhythm - Regular
Rate - Normal or Slow
QRS Duration - Prolonged
P Wave - Ratio 2:1, 3:1
P-R Interval - Normal or prolonged but constant
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3rd Degree Block
Rhythm - Regular
Rate - Slow
P Wave - Unrelated
P-R Interval - Variation
Complete AV block. No atrial impulses pass through the
atrioventricular node and the ventricles generate their own rhythm
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Bundle Branch Block
Rhythm - Regular
Rate - Normal
P Wave - Ratio 1:1
P Wave rate - Normal and same as QRS rate
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Premature Ventricular Complexes
Rhythm - Regular
Rate - Normal
P Wave - Ratio 1:1
P Wave rate - Normal and same as QRS rate
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Premature Ventricular Complexes (cont.)
2 odd waveforms, these are the ventricles depolarizing
prematurely in response to a signal within the ventricles
(Above – unifocal PVC's as they look alike if they differed in
appearance they would be called multifocal PVC's, (as below)
)
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Junctional Rhythms
Rhythm - Regular
Rate - 40-60 Beats per minute
P Wave - Ratio 1:1 if visible. Inverted in lead II
P Wave rate - Same as QRS rate
P-R Interval - Variable
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Ventricular Tachycardia (VT) Abnormal
Rhythm - Regular
Rate - 180-190 Beats per minute
P Wave - Not seen
Results from abnormal tissues in the ventricles generating
- A rapid and irregular heart rhythm.
- Poor cardiac output is usually associated with this rhythm
thus causing the pt. to go into cardiac arrest.
Shock this rhythm if the patient is unconscious and without
a pulse
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Ventricular Tachycardia (physiology)
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Ventricular Tachycardia (VT) Abnormal(Cont.)
Rhythm - Irregular
Rate - 300+, disorganized
QRS Duration - Not recognizable
P Wave - Not seen
This patient needs to be defibrillated!! QUICKLY
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Ventricular Fibrillation (Physiology)
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Ventricular Ectopic Beat (Physiology)
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Asystole - Abnormal
Rhythm - Flat
Rate - 0 Beats per minute
QRS Duration - None
P Wave - None
Carry out CPR!!
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Myocardial Infarct (MI)
Rhythm - Regular
Rate - 80 Beats per minute
P Wave - Normal
S-T Element does not go isoelectric which indicates infarction
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Areas of the ECG to be concentrated upon to
study the events e.g. MI
Position Leads
Lateral look on lead I,V5 ,V6
Inferior look on lead II ,III ,aVF
Anterior/ Septal look on V1,V2,V3,V4
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Ventricular hypertrophy
Left Ventricular Hypertrophy (LVH)
1 LVH is age- dependent
A negative T wave in lead V6 after 7 days of life ,think of LVH
2 In infancy: the mean QRS being moved to the left and posteriorly.
In frontal plane, the QRS axis may move to 0 -60◦; <30◦in an infant
is very uncommon and suggests LVH
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Left Ventricular Hypertrophy (Physiology)
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Left Ventricular Hypertrophy (LVH) (Cont.)
3 Without an axis shift, the diagnosis of LVH is based on voltage criteria:
- R waves less than 5th percentile or S waves more than 95th percentile
in V3R and V1
- R waves more than 96th percentile in V5 and V6
4 In older adolescents: LVH causes an exaggerated:
- Negative deflection in V1
- Positive deflection in V6
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Right Ventricular Hypertrophy (RVH)
1 The term infant: has physiological “normal” right ventricular hypertrophy
2 For pathological RVH ,the mean QRS will move farther right and anteriorly.
In frontal plane QRS axes >190◦ for infant <1 week of age or 135◦ for infants
> 1month of age
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Right Ventricular Hypertrophy (RVH) (cont.)
3 A “pure” R wave > 25 mm voltage ,or a qR pattern in the
right chest leads-this suggests pathologic RVH in the newborn
4 An upright or even “flat” T wave in V4R and V1 in a child
between 1 week and 8 years of age is highly suggestive of RVH
5 In an older adolescents, ECG criteria for RVH are:
*Right axis deviation
*Increased R voltage in V1 or S in V6 and rsR’ in V1
*ST segment depression and a flipped T wave in V1
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Conduction disturbances
Atrioventricular (AV) Blocks:
1˚AV block:
Prolongs the PR interval more than normal for age and by > 200 ms
(1 big square) beyond 16 years
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2◦ AV block results in 2 main patterns:
Mobitz I:
· Wenckebach phenomenon involves progressive prolongation of
the PR interval until there is a drop in QRS (Ventricular beat)
· Rarely requires treatment
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2◦ AV block results in 2 main patterns:
Mobitz II:
· Normal PR interval ,but ,periodically ,there is a drop in QRS
*2:1 AV block is 2 P waves for each QRS
*3:1 AV block is 3 P waves for each QRS
· Higher-grade heart block implies disease of the His-Purkinje
conduction system
· Often requires a pacemaker
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3◦ AV block or complete heart block
No atrial depolarizations are conducted through the AV node
· If the QRS complex has a normal width (< 100 ms), there is a
Junctional ectopic pacemaker
· Junctional escape rate is 40 -60 bpm, whereas ventricular escape
rate (Which also would be a wider QRS) is 20 -40 bpm
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Bundle Branch Block (BBB)
LBBB
Is rare in children
The QRS is prolonged, with a duration of 120 -180 ms
(3 -4.5 small squares)
An RR’ (notched or slurred ) in the lateral leads (I , aVL and V6 )
and there is a corresponding SS’ (also called QS ) in V1
50% of patients have a normal axis ,50% have LAD ( -30◦ to -90◦ )
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Bundle Branch Block (BBB) (cont.)
RBBB
More common in children, particularly after open heart surgery
RR’ or RSR’ (“rabbit ears “) in V1 and a wide S wave in V6
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References
• http://www.davita-shop.co.uk/ecg-instruments.html
• http://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/normal_durat
ion.php
• http://www.pedcard.rush.edu
• http://www.rnceus.com/ekg/ekgst.html
• http://www.ambulancetechnicianstudy.co.uk/rhythms.html
• http://www.learntheheart.com/cardiology-review
• http://www.zuniv.net/physiology/book/chapter11.html
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