Download Obtaining a High Quality ECG and Basic ECG

Pediatric ECG
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ECG Basics: What is
an ECG?
ECG Basics: ECG
interpretation.
ECG Basics:
Acquiring an ECG.
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ECG Basics I
● ECG is a tracing of the heart's electrical activity from
different “views” (=leads)
● Each “view” (= lead) produces a wave with height
(mm) and duration (msec)
● WAVES are: P, QRS, T
● Intervals contain a WAVE and a SEGMENT:
○ PR and QT intervals
● Segments are time between WAVES
○ ST Segment
ECG Basics II
● There are normal ranges for age for the:
○ HEIGHTS of the waves
○ DURATIONS of the waves, intervals and segments
○ AXIS of the waves in the Frontal plane
ECG Basics III
● 12 Leads:
○ FRONTAL=LIMB: I, II, III, aVF, aVL, aVR
○ HORIZONTAL=PRE-CORDIAL: V1, V2, V3, V4, V5, V6
● The AXIS of any wave = the direction the wave “POINTS” in the
FRONTAL PLANE of the body
ECG Basics IV
ECG Basics V
ECG Basics VI
● FRONTAL plane is based on LIMB LEADS
● One can estimate the DIRECTION that the
ECG WAVE vector points in the FRONTAL
plane
● Simple approach is to just examine LIMB
LEADS I and aVF
● In this way the AXIS of the heart's electrical
signal is determined relative to the
FRONTAL plane of the body
ECG Basics VII
● QRS is UPRIGHT in LEAD I, therefore it is
pointing towards LEAD I, somewhere
between +90 and -90 degrees
ECG Basics VIII
● QRS is UPRIGHT in LEAD aVF, therefore the
AXIS is somewhere between 0 and +90 degrees
● All waves (P, QRS, T) have AXIS in the
FRONTAL plane with normals for age
ECG Basics IX: Normal QRS AXIS for AGE
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ECG Basics: Lead Placement I
ECG Basics: Lead Placement II
● Remove all clothing/jewelry from waist up
● Clean skin site with an alcohol pad, dry with a gauze pad; shave hair if
necessary
● When reapplying electrodes, ensure any gel residue is removed and
electrodes changed.
● Electrodes must always be kept in an air-tight container ==========>
● Good skin preparation prior to electrode attachment is very important
○ Poor skin-electrode contact leads to artifact
ECG Basics: Lead Placement III
● RL- On right leg (inside calf, midway between ankle and calf muscle)
● LL- On left leg (inside calf, midway between ankle and calf muscle)
● RA- Right arm (on the inside, halfway between wrist and elbow)
● LA- Left arm (on the inside, halfway between wrist and elbow)
● V1- 4th intercostal space, at right sternal margin
● V2- 4th intercostal space, at left sternal margin
● V3- Midway between V2 and V4
● V4- 5th intercostal space at left midclavicular line
● V5- Same transverse level as V4, at anterior axillary line
● V6- Same transverse level as V4, at left midaxillary line
ECG Basics: Lead Placement IV
ECG Basics: Lead Placement V
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Examples of Poor
Tracings
Pediatric ECG: Interpretation
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ECG Scale
Values
RATE
Calculation
Rhythm
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ECG Basics: Scale
● Standard paper speed (horizontal scale) is
25mm/sec
● Standard vertical scale 10.0mm = 1mV
● Small box =
= 1mm x 1mm
= 40 msec x 0.1 mV
● VERTICAL values are typically in mm
● HORIZONTAL values are typically in msec
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Rate: Calculation
● Standard paper speed is 25mm/sec
● Therefore:
○ Each little box is 0.04 seconds = 40 msec
○ Each big box is 0.2 seconds = 200 msec
● Therefore to determine HEART RATE:
○ Count the # of big boxes between QRS beats
○ Divide 300/(# big boxes) = RATE (or)
○ Divide 60,000/time in msec = RATE
Rate: Examples
● Therefore to determine HEART RATE:
○ Count the # of big boxes between QRS beats
○ Divide 300/(# big boxes) = RATE (or)
○ Divide 60,000/time in msec = RATE
3 boxes =
600 msec
HR=100
4 boxes =
800 msec
HR=75
Rate: Normals
Rate: Normals
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Rhythm I
● Normal Sinus Rhythm definition:
○ P-wave AXIS is UPRIGHT
in I and aVF
○ P-wave before every QRS
○ QRS after every P-wave
○ Normal PR interval
Rhythm II
● Automatic ECG machine read for rhythm is
in general very reliable
● Basics:
○ Early = Premature beats are common
in the general population and in
isolation are not typically dangerous
○ All tachycardias are abnormal and
concerning
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P-Wave
● Atrial depolarization
● Normal Morphology = upright in limb leads I, II and aVF
Atrial Enlargement
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PR Interval
● Definition = time from the beginning of the Pwave to the beginning of the Q-wave
PR Duration Normals (=PR interval)
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QRS Wave
● Ventricular depolarization
Abnormal Length
Abnormal Morphology
Abnormal Size (=height) LEAD V1
Abnormal AXIS
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QRS Duration Normals
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QRS Morphology Abnormals
● Incomplete RBBB
● RBBB
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Incomplete RBBB – borderline long QRS
duration of 90-100msec, with a rSR’ –
“rabbit ears” in V1. This is a frequent
normal variant.
Real RBBB = pathologic, wide QRS, typically
after heart surgery, very unusual in a peds
patient who has not has cardiac surgery; should
be evaluated
LVH: S Wave in V1
RVH: R wave in V1
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QT Interval: Avoiding Toxicity
● Careful review of SCREENING ECGs, including QTc interval will be key to
minimizing risk.
● Those with clearly prolonged QTc will be excluded from study.
● Once a patient passes screening, the focus of the serial ECG will be on
accurately measuring and calculating QTc
● The automated readings by the ECG machine is generally quite accurate - as
long as:
○ The ECG is high quality with clearly seen T-waves and minimal baseline
artifact
○ The HR is within the normal range for age
QT Interval: Poor Quality ECG Tracings
QT Interval: Poor Quality ECG Tracings
QT Interval: Poor Quality ECG Tracings
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More on QTc
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QT Interval: How to Measure.
● Definition = time from the start of the QRS
to the end of the T-wave
● Measured in LIMB LEAD II or V5
● Correct for HR using
○ QTc = “QT-corrected”
○ QTc =
○ Frederica Correction
○ RR=time between “R-waves”
○ RR in SECONDS
● Upper limit of Normal Duration =
QTc<455msec
QT Interval: How to Measure.
QTc=
● RR interval =14.5 boxes
=14.5 x 40msec
=580msec
=0.58sec
=0.8339
● QT=9.5 boxes
=380msec
● Therefore the QTc = 380/0.8339
=456msec
ONLINE CALCULATOR
https://www.medcalc.org/clinicalc/corrected-qt-interval-qtc.php
QT Interval: HR, RR and cubed root Table.
QTc
=
Adverse Event Grading: Appendix V
Cardiac Toxicity Management: Appendix VI
Prolonged QTc can lead to Ventricular Tachycardia (VT)
Prolonged QTc can lead to Ventricular Tachycardia (VT)
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T-waves
● Ventricular RE-polarization
Abnormal Morphology
ST Segment
● Definition = time from the end of the QRS
to the beginning of the T-wave
● Normal ST-segment is FLAT = on the
same horizontal level as the TP and PR
intervals
ST Segment and T-waves
● Automatic ECG machine read on ST-segment and
T-waves is in general very reliable
● Basics:
○ ST-segment should be FLAT
■ Can be +/- 1mm
○ T-Waves AXIS in FRONTAL PLANE is 0 to +60
○ T-Waves are UPRIGHT in V4-V6
○ T-Waves are NEGATIVE in V1-V3 from infancy
to early adolescence
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CONTACT and REFERENCE MATERIALS
James Nielsen, MD
● EMAIL: [email protected]
● SKYPE (USA NUMBER): 917-623-7806
Drug List – QT Problem
● FAX (USA NUMBER): 1-888-252-2907
https://www.crediblemeds.org/
QUINTILES:
● Investigator ECG Manual:
https://drive.google.com/open?id=0B6mKMisaYx1cMkhrZm40cVhFdVE
● VISIT CODE POSTER:
https://drive.google.com/open?id=0B6mKMisaYx1cX1lVUkdPVF9hR0E
● ECG ABNORMALITY CRITERIA:
https://drive.google.com/open?id=0B6mKMisaYx1cYk9LeW1KbV9paEk
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