Kendra M. Ward, MD, Barbara J. Deal, MD
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• Screening for congenital or acquired heart disease.
• Follow-up of established cardiac disorders:
• Evaluation of apparent life-threatening event, syncope, chest
pain, or new-onset seizure.
• Arrhythmia detection and evaluation.
• Evaluation of conduction disorder.
• Monitoring cardiac effects of medication.
• Evaluation for appropriate pacemaker or defibrillator function.
• Evaluation of cardiac effects of electrolyte or metabolic abnormalities.
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• Disorders that limit access to skin of chest
wall, such as thoracic wound.
• Extensive bandages over chest.
• Third-degree skin burns.
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• Improper lead positioning is a major source of
abnormal tracings.
• The most common recording error is limb lead reversal.
• Automated ECG interpretations that read “left atrial rhythm” usually
reflect limb lead reversal.
• Negative P, QRS, and T waves in leads I and aVL are another indicator
of lead reversal.
• Make sure the initial recording is at the appropriate speed: 25
mm per second, and appropriate gain: 10 mm per mV.
• Eliminating as much patient movement as possible is essential;
blowing bubbles over young children often allows time for recording
without movement.
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• Clean the area with alcohol swab.
• Skin must be clean and dry.
• Leads cannot be placed over bandages: either reposition bandage
or omit lead.
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• Supine position is essential.
• Some patients have T wave changes in upright positions, and decubitus
positioning may slightly alter the location of the heart relative
to the ECG leads.
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• Lead placement is important and must be consistent.
• Inappropriate placement of limb or precordial leads results in
interpretation errors, including hypertrophy or infarct patterns.
• Figure 23–1 shows placement of
leads.
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• RA: Right forearm, distal to insertion
of deltoid muscle.
• LA: Left forearm, distal to insertion of deltoid muscle.
• RL: Right leg.
• LL: Left leg.
• V1: Fourth intercostal space, right sternal edge.
• V2: Fourth intercostal space, left sternal edge.
• V3: Halfway between V2 and V4.
• V4: Fifth intercostal space, midclavicular line.
• V5: Same level as V4 on anterior axillary line.
• V6: Same level as V4 on midaxillary line.
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• Place electrode stickers appropriately.
• Attach the leads, with careful attention to limb lead placement.
• Enter the patient data into the ECG machine. ECGs without name,
age, and date cannot be officially interpreted.
• Select gain and paper speed (standard speed 25 mm per second
and standard gain 10 mm per mV).
• Use standard settings initially.
• Modify gain as needed.
• Select the type of tracing desired.
• 12-lead ECG.
• 12-lead rhythm strip.
• 3-lead rhythm strip.
• Ensure the patient is still and the tracing is stable on the monitor
of the ECG machine.
• Once there is no artifact, record.
• Inspect the tracing before disconnecting the leads.
• If no additional tracings are needed, disconnect the leads and
remove the electrode stickers.
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• To avoid missing important information, interpret
ECGs consistently and systematically.
• Knowledge of the patient’s age is essential because
standards are age-dependent.
• ECGs in children should be interpreted by clinicians specifically
trained in pediatrics because of the significant age-related differences
from adult ECGs.
• Evaluate rate, rhythm, axis, intervals,
hypertrophy, ST segments.
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• Normal P wave axis is upright in leads I and
aVL.
• Left atrial rhythm, or limb lead reversal, shows negative P wave
in leads I and aVL.
• Low atrial rhythm shows negative P wave in inferior leads: II,
III, aVF.
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• Normal frontal QRS axis is age-dependent.
• Neonates have relatively rightward QRS axis (+40 to +180
degrees), which gradually shifts toward left with age.
• Left axis deviation or superior axis (0 to –90 degrees)
in neonate is highly suggestive of congenital heart disease, particularly
among infants with Down syndrome.
• Left axis deviation or superior axis is also associated with the
following:
• AV septal defects (primum atrial septal defects).
• Tricuspid atresia.
• Underdevelopment of right ventricle.
• Left ventricular hypertrophy.
• Preexcitation.
• Right axis deviation is suggestive of right ventricular hypertrophy
or underdevelopment of left ventricle.
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• Measured from onset of P wave to onset of QRS.
• Normal PR interval is age-dependent, usually < 160 msec in
young children.
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First-Degree
AV Block
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• PR interval greater than expected for age.
• Associated with atrial septal defects, rheumatic fever, ectopic
atrial rhythms.
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Second-Degree
AV Block
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• Type I (Wenckebach).
• Successive PR lengthening until atrial impulse is not conducted
(generally does not progress).
• May be normal variant, particularly during sleep.
• Type II.
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Third-Degree
AV Block
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• Failure of an atrial impulse to be conducted
to the ventricles.
• Never a normal variant but needs to be differentiated from accelerated
junctional or ventricular rhythms.
• Congenital form associated with autoimmune disorders or complex
congenital heart disease.
• Acquired form secondary to surgical repair of congenital heart
disease.
• Congenitally corrected transposition of the great arteries.
• Myocarditis.
• Lyme disease.
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• Reflects ventricular depolarization.
• Normal.
• Prolonged QRS duration for age reflects right or left ventricular
conduction delay or block (> 120 msec in adults).
• Right ventricular conduction delay may be associated with atrial
septal defects.
• Right bundle branch block is seen after surgical repair of some
forms of congenital heart disease, especially tetralogy of Fallot.
• Left bundle branch block is rare and usually associated with
surgical repair of lesions obstructing left ventricular outflow
tract or with significant cardiomyopathy.
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• Measured from onset of QRS to end of T wave.
• Reflects ventricular depolarization and repolarization.
• The normal QT interval of 400 msec is based on a heart rate of
60 bpm.
• Rate-corrected QT interval = QTc.
• Bazett’s correction: Measured QT interval/square
root of RR interval.
• Normal QTc.
• A prolonged QT interval increases the risk for potentially life-threatening
arrhythmias and may result in the long QT syndrome (a cardiac ion
channelopathy) or as an acquired abnormality from drug, electrolyte,
or nervous system disorders.
• Patients with seizures, syncope, or hearing loss should be screened
for QT abnormalities.
• A prolonged QT interval may require cardiac consultation.
• QT prolongation may be intermittent; therefore, a normal QT interval
does not preclude the presence of long QT syndrome.
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Right Atrial
Enlargement
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• Tall pointed P waves.
• Amplitude > 2.5 mm.
• Best seen in leads II, III, V1.
• Associated with the following:
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Left Atrial
Enlargement
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• Increased P wave duration (> 90–100
msec).
• Biphasic P wave in V1 with deep negative component.
• Associated with large left to right shunts and mitral valve disease.
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Ventricular
Hypertrophy
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• ECG diagnosis of hypertrophy is sensitive but
not specific, resulting in frequent overinterpretation of hypertrophy.
• Thin chest wall, anemia, volume overload, and athletic training
may contribute to ECG appearance of ventricular hypertrophy.
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Left Ventricular
Hypertrophy
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• Voltage criteria include tall R waves in left
precordial leads V5–V6 > 98 percentile for age, or deep
S waves in V1–V2.
• Sum of R wave in V6 and S wave in V1 or V2 > 98 percentile for
age.
• Deep Q waves in inferior limb leads or left precordial leads.
• Seen with the following conditions:
• Patent ductus arteriosus.
• Lesions obstructing left ventricular outflow tract, such as aortic
stenosis or coarctation.
• Hypertension.
• Sickle cell anemia.
• Cardiomyopathy.
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Right Ventricular
Hypertrophy
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• Voltage criteria include increased R wave amplitude
in right precordial leads V1–V2 > 98 percentile for age.
• A Q wave in V1 is never normal and suggests right ventricular
hypertrophy or ventricular inversion.
• Upright T wave in right precordial leads after the first week
of life, and before “adult” ECG pattern is achieved, indicates
right ventricular hypertrophy.
• Deep S wave amplitude in V6 suggests right ventricular hypertrophy;
usually > 7 mm.
• An rSr′ pattern is a common normal
variant in children; however, a tall R′ is
not normal.
• Seen when lesions obstruct right ventricular outflow tract, such
as in cases of pulmonic stenosis and tetralogy of Fallot.
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Biventricular
Hypertrophy
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• Voltage criteria for both right and left ventricular
hypertrophy.
• Katz-Wachtel criteria for biventricular hypertrophy: Large combined
voltages of R + S wave amplitude in V4 > 60 mm.
• Associated with the following:
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• Normal ST segment horizontal, isoelectric.
• Can be normal to have 1 mm elevation or depression of ST segment
in limb leads.
• Left precordial leads may have up to 2-mm elevation or depression
of ST segment.
• Beware of calling ST changes normal if they are a change from
a previous ECG or if the patient has chest pain or other cardiac
symptoms.
• J point elevation is a normal finding.
• ST changes can be seen in the following:
• Myocardial ischemia.
• Myocarditis.
• Pericarditis.
• Abnormal potassium levels.
• Digitalis.
• Left ventricular hypertrophy with “strain.”
• Central nervous system pathology.
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• Short PR interval in sinus rhythm, associated
with a slurred upstroke to QRS (delta wave).
• The term “Wolff-Parkinson-White syndrome” refers
to the association of preexcitation pattern on ECG with supraventricular
tachycardia.
• Left axis deviation or the absence of a Q wave in V6 may be subtle
indicators of preexcitation.
• Preexcitation may be intermittent, and it may be associated with
the development of supraventricular tachycardia in about 30–35% of
cases.
• Due to the small but present risk of life-threatening arrhythmias
as the initial symptomatic event with preexcitation, patients with
this finding on ECG should be referred for cardiac consultation.
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Rate: Too Fast or Too Slow?
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Rhythm: Regular
or Irregular?
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QRS Complex:
Wide or Narrow?
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What Is the
P/QRS Relationship?
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• 1:1 P/QRS ratio.
• If P wave precedes QRS with constant PR interval, consider
sinus or atrial rhythm.
• Analyze P wave morphology to distinguish between these rhythms.
• If QRS precedes P wave, consider ventricular or junctional rhythm,
or reciprocating rhythms with retrograde conduction to atria (supraventricular tachycardia).
• If there are more P waves than QRS complexes, consider atrial
arrhythmia (ie, atrial flutter, atrial tachycardia).
• If there are more QRS complexes than P waves, consider junctional
or ventricular rhythm.
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• Depends on the reason the test was obtained,
the patients’ clinical status, and the ECG findings.
• Patients with abnormal ECGs should be referred to a pediatric
cardiologist; the timing of referral depends on both the ECG finding
and the clinical context.
Deal BJ, Johnsrude CL, Buck SH. Pediatric ECG
Interpretation: An Illustrative Guide. Futura, Blackwell Publishing; 2004.
Park MK, Guntheroth WG. How to Read
Pediatric ECGs. 3rd edition. St. Louis: Mosby-Year Book; 1992.