PAED ECG Flashcards
Describe the differences between an infants & adults anatomy, ECG & HR
In infants the RV is larger & thicker then the LV.
It produces an ECG therefore that indicate right ventricular hypertrophy with T wave inversions in V1-V3 and a dominant R wave in V1
The PR & QRS intervals are longer in infants and shorter in adults, this is due to a smaller heart size in infants.
As the child grows older the heart rate decreases
Where are the ECG leads placed on an infant?
V1: 4th intercostal space on the right sternal border
V2: 4th intercostal space on the left sternal border
V3: Placed on the 5th rib diagonal to V2, needed for V4R
V4R: 5th intercostal space at the right mid-clavicular line
V5: anterior axillary line, horizontal to V4
V6: mid axillary line, horizontal to V4
V4R is needed to replace V4 as infants/ young kids heart’s lie more to the right side and shift more towards the left as they grow
Describe the process of ECG interpretation in pediatrics
A pediatric cardiologist should review all children ECGs
There is difficulty placing the precordial leads
Make sure to put arm leads the correct way round, otherwise it causes false P waves
Leads are placed on each arm & left leg
How do we determine the rhythm in a pediatric ECG
First identify the lead with the least artefact or use lead II
Calculate the approx HR by counting boxes between QRS complexes
The rate= 300/ number of L boxes between QRS
How does the resting heart rates of pediatrics vary with age?
From newborn to teenager, their HR decreases as they grow. e.g., due to small heart size and a faster metabolism
Newborn: 110-150bpm
2 years: 85-125bpm
4 years: 75-115bpm
6 years: 60-100bpm
14 years: 60-120 bpm
Describe sinus rhythm and sinus arrythmia in paeds
Sinus Rhythm can be identified by having a consistent PR interval throughout the trace, The P wave is positive in Lead II & AVF, but negative in AVR
In Sinus arrhythmia there is a variation in sinus rhythm as when respiring the heart falls and rises
PR intervals & P waves are normal. It is a normal irregularity that occurs during breathing.
This is due to the underdevelopment of the ANS leading to noticeable fluctuations in HR during breathing
Describe sinus bradycardia in Paeds
It is a slow HR that is expected of their age, can be lower than 60bpm due to SA node sending signals at a slower pace
Sinus bradycardia can be low for children with great aerobic capacity
To determine SB: we count number of L boxes between QRS complexes
Rate=300/number of L boxes =HR
Describe sinus tachycardia in paeds
It refers to a faster-than-normal sinus rhythm exceeding that of a 100bpm, most likely associated with anxiety, fever or stress.
ST has a regular rhythm but the rate is accelerated
To determine ST: we count number of L boxes between QRS complexes
We would expect their to be fewer boxes between complexes to give a greater HR
There should be clear P waves before each QRS complex, positive in Lead II
Describe how the QRS axis (hexaxial axis) varies with age
The normal axis for kids is between -30 to +90, abnormalities can indicate conduction issues, however the axis can vary with age
Infants The QRS axis in newborns is often rightward (between +30° to +180°). The rightward axis is a normal finding due to the right ventricle’s relatively large size and the heart’s initial orientation at birth.
1-month to 3 month: axis ranges from +10 to +125
3 months to 3 years: axis ranges from +10 to +110
Over 3 years: axis ranges from +20 to +120
Adult range: axis ranges from +30 to +105
How do we evaluate intervals?
- Use Lead II or lead with least artefact to examine PR, QRS & QT intervals
- PR is measured in seconds
- QT measured in Milliseconds
- Both values are measured
How do we evaluate the P wave amplitude and duration in pediatrics
Amplitude: less than 3mm
Duration: in children less than 0.09, infants 0.07 seconds
Interval range: between 0.02 to 0.20 seconds, this varies with age
P waves should be consistent and come before QRS.
P waves should be positive in lead II, I, AVF and AVR
How do we evaluate the QRS amplitude & duration in pediatrics
Amplitude: between 6-10mm in precordial leads and 3-6mm in limb leads
Duration: QRS should range from 0.04 to 0.09 seconds, a wide QRS is greater than 0.08secs
Interval: a greater interval than 0.09 may indicate a delay in conduction e.g., LV hypertrophy
The corrected QT interval (QTc) is generally calculated using the Bazett formula or other correction formulas based on the heart rate. In children, the QTc should generally be less than 450 ms
Normal QRS= 1 S box
Wide QRS= 3 S boxes
Describe Q waves in pediatrics
Normal Q waves have an average of 0.02secs, less than 0.03secs
Usually less than 5mm deep in AVF and left precordial leads
Maybe as deep as 8mm in children under 3yrs in lead III
Describe QT & T waves in pediatrics
Use lead II or lead with the least artefact
Qtc is calculated via bazette formula.
A normal Qtc for an infant is less than 0.49 seconds
Older than 6 months: less than 0.44 seconds
The normal range is between 0.4 +-0.014
Define the bazette formula
PR interval is measured by counting S boxes between intervals
RR= S boxes x 0.04 secs
QT is measured from beginning of QRS to the end to T wave.
QT= S boxes x0.04secs
QTc= QT/√RR
BF=HR=220-age/√duration
How does T wave change over time as the child grows?
Newborn: T waves are upright through V1-V6
Week 1+: T waves becomes inverted in V1-V3, inversion remains until age 8
8 years+: T wave becomes upright once again in V1-V3
T wave inversion is often asymptomatic and benign, resolved as child grows
This is due to an immature conduction system which is resolved with age as the child grows.
It can be due to the heart being more vertical compared to later stages of childhood when the heart shifts to a more horizontal position. This vertical position of the heart leads to different depolarization and repolarization vectors
Describe the ST segment in pediatrics
ST represents the interval between ventricular depolarization & ventricular repolarization
Measured from the beginning of the T wave
Normally isoelectric (at 0)
In infants & kids ST can be depressed/elevated up to 1mm in limb leads and 2mm in V1-V6, that is normal range
Describe T & U waves in pediatrics
T waves: Represents ventricular repolarisation
- Dome shaped & asymmetrical limbs
- Upright mostly apart from V1/V2, AVR & AVL
U wave:
- Represents repolarisation of purkinje fibers
- It comes after the T wave and before the P wave
- A slight positive deflection
- The amplitude is 5mm or less in leads I-III, 10mm or less in precordial leads (V1-V6)
Duration is not measured
