Use of medications for attention-deficit hyperkinetic disorder and preparticipation sports physical examination has led to an increase in number of electrocardiograms (ECG) performed during adolescence. Interpreting ECGs in children and young adults must take into account the evolutionary changes with age and the benign variants, which are usually not associated with heart disease. It is crucial for primary-care providers to recognize the changes on ECG associated with heart disease and risk of sudden death. In this article, the significance, sensitivity, specificity, and the diagnostic workup of these findings in the asymptomatic teenager are discussed.
Key points
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Electrocardiograms (ECGs) in children and young adults need to be interpreted by an individual trained in reading pediatric ECG, because the computerized interpretation of ECGs is fraught with errors.
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ECGs in children may show age-related evolutionary changes, normal variation, or abnormal findings representing cardiac disease.
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In this article, the ECG findings that may be encountered in an asymptomatic teen are discussed. Some findings may be benign and do not require further testing, whereas others may have a higher likelihood of being associated with heart disease or risk of sudden death. Personal history, family history, and the specific ECG findings dictate further management, which is discussed in detail.
Introduction
Electrocardiograms (ECGs) are performed in children and young adults as a part of evaluation for symptoms and signs related to the cardiovascular system, such as palpitations, chest pain, syncope, or cardiac murmurs; a screening test before sports participation or initiation of medications in conditions such as attention-deficit hyperkinetic disorders (ADHD). The ECG in the young shows evolutionary changes with age as well as benign variants seen in a few normal individuals. However, there are certain findings detected in asymptomatic teenagers with potential clinical significance that may require further investigations and management. These abnormal findings in asymptomatic individuals have a sensitivity of 51%, specificity of 61%, positive predictive accuracy of 7%, and negative predictive accuracy of 96% for identifying cardiovascular abnormalities. In this article, the benign and potentially significant ECG findings in asymptomatic teenagers and their management are discussed.
Introduction
Electrocardiograms (ECGs) are performed in children and young adults as a part of evaluation for symptoms and signs related to the cardiovascular system, such as palpitations, chest pain, syncope, or cardiac murmurs; a screening test before sports participation or initiation of medications in conditions such as attention-deficit hyperkinetic disorders (ADHD). The ECG in the young shows evolutionary changes with age as well as benign variants seen in a few normal individuals. However, there are certain findings detected in asymptomatic teenagers with potential clinical significance that may require further investigations and management. These abnormal findings in asymptomatic individuals have a sensitivity of 51%, specificity of 61%, positive predictive accuracy of 7%, and negative predictive accuracy of 96% for identifying cardiovascular abnormalities. In this article, the benign and potentially significant ECG findings in asymptomatic teenagers and their management are discussed.
Normal variants
Findings like sinus arrhythmia, sinus bradycardia, sinus tachycardia, right ventricular conduction delay, or incomplete right bundle branch block without right ventricular hypertrophy (RVH) or right axis deviation, isolated intraventricular conduction delay, right axis deviation in patients 8 years of age or younger, early repolarization, normal variant of ST-T elevation, juvenile T wave pattern, QTc 0.45 seconds or greater reported by computer but normal by manual calculation, and borderline QTc 0.44 to 0.45 seconds without significant family history do not require any further testing or evaluation ( Box 1 ). These findings are not associated with heart disease and are termed normal variants. Trained athletes (≤80%) may show sinus bradycardia, first-degree atrioventricular (AV) block, and or early repolarization, which result from physiologic adaptation of the cardiac autonomic nervous system to athletic conditioning.
- 1.
Sinus arrhythmia
- 2.
Sinus bradycardia
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First-degree atrioventricular block
- 4.
Wenckebach phenomena
- 5.
Incomplete right bundle branch block (without RVH or right axis deviation)
- 6.
Early repolarization
- 7.
Right axis deviation 8 years of age or younger
- 8.
Juvenile pattern of repolarization
Abnormal ECG findings in asymptomatic teenagers
Computerized ECG readouts must be treated with caution, because they are fraught with errors in interpretation and measurements. ECG findings that may be suggestive of heart disease are regarded as abnormal findings. Abnormal ECG findings that are confirmed by trained individuals for reading pediatric ECGs are discussed in the following section. These findings can be seen in asymptomatic individuals and may be related to the altered autonomic tone or structural remodeling secondary to intense physical training, or can be a true indicator of significant heart disease. Based on the type, intensity, and level of training, varying degrees of abnormal ECGs are seen in about 40% of athletes. The most common changes detected include early repolarization, chamber hypertrophy, repolarization abnormalities, and deep Q waves. Some of the abnormal ECG findings have a low likelihood of being related to cardiac abnormality; however, there are other findings that would warrant further evaluation to rule out life-threatening cardiac conditions. Further evaluation in these asymptomatic teenagers with abnormal ECG findings is dependent on the indication for obtaining an ECG, personal and family history, physical examination, and the abnormality detected on the ECG ( Box 2 ).
- 1.
Voltage criteria for chamber enlargement or hypertrophy
- 2.
Axis deviation
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Right axis deviation (>8 years of age)
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Left axis deviation
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- 3.
Abnormal rhythm
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Escape rhythm
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- 4.
Ectopies
- 5.
Bundle branch block pattern
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Left bundle branch block
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Right bundle branch block ± axis deviation
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- 6.
AV block
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Second-degree type II AV block
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Third-degree AV block
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- 7.
Wolff-Parkinson-White pattern
- 8.
Abnormal repolarization
- 9.
Abnormal QT interval
Chamber Enlargement or Hypertrophy
The principal ECG changes associated with hypertrophy or enlargement of cardiac chambers are associated with amplitude, duration of complexes, and vectors of corresponding complexes and segments. There are age-specific criteria for left ventricular hypertrophy (LVH) and RVH based on the normal data established for infants and children.
Detection of LVH in pediatrics, using ECG, has a sensitivity of only 25% to 30% when compared with echocardiogram. The commonly used criteria in pediatrics includes the QRS amplitude greater than the upper limits of normal for age, the adaptation of adult criteria for LVH, presence of axis deviation, deep Q waves, and the presence of repolarization abnormalities. The most widely accepted adult criteria for LVH ( Box 3 ) include the voltage criteria by Sokolow-Lyon, the Cornell voltage criteria, and the point score of Romhilt and Estes. Even although the specificity of an individual criterion for LVH is high, the sensitivity is poor. QRS voltages are influenced not only by left ventricular size or mass but also by other factors like age, gender, race, body habitus, and sites of electrode placement. Their effect contributes to the limited accuracy of the ECG criteria. Use of ECG criteria for LVH with ST segment and T wave abnormalities increases the specificity and sensitivity to detect LVH ( Fig. 1 ).
LVH:
- 1.
QRS voltage greater than upper limits of normal for age
- 2.
Sokolow-Lyon criteria: (SV1 or V2 + RV5 or V6) 35 mm or greater
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Cornell criteria: (RaVL + SV3) 28 mm or greater for men and 20 mm or greater for women
- 4.
Point score of Romhilt-Estes: (LVH, 5 points; probable LVH, 4 points)
- 1.
Amplitude (3 points)
Any of the following:
- a.
Largest R or S wave in the limb leads 20 mm or greater
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S wave in V1 or V2 30 mm or greater
- c.
R wave in V5 or V6 30 mm or greater
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ST-T segment changes (typical pattern of left ventricular strain with the ST-T segment vector shifted in direction opposite to the mean QRS vector)
Without digitalis (3 points)
With digitalis (1 point)
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Left atrial involvement (3 points)
Terminal negativity of the P wave in V is 1 mm or more deep with a duration of 0.04 seconds or more
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Left axis deviation –30° or more (2 points)
- 5.
QRS duration 0.09 seconds or more (1 point)
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Intrinsicoid deflection in V5, V6 0.05 seconds or more (1 point)
- 1.
- 5.
Associated QRS axis deviation, secondary ST-T changes and deep Q waves
RVH:
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QRS voltage in the right precordial leads greater than upper limits of normal for age
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Right axis deviation
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Secondary ST-T changes, based on evolutionary changes
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Presence of Q waves in the right precordial leads
Biventricular hypertrophy:
- 1.
Presence of criteria for both LVH and RVH
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Right axis deviation in presence of LVH
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Combined tall R waves and deep S waves in the midprecordial leads greater than 60 mm (Katz-Wachtel criteria)
Left atrial abnormality:
- 1.
P wave duration 120 milliseconds or greater
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Widely notched P wave 40 milliseconds or greater
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Left axis of the terminal P wave between –30° and –90°
Right atrial abnormality:
- 1.
Increase in amplitude of the P wave
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Rightward shift of the P wave vector
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Prominent initial positivity of the P wave in V1 or V2 1.5 mm or greater
The sensitivity of criteria for RVH is even lower. The criteria for RVH include voltage criteria with QRS amplitudes greater than upper limits of normal for age in the right precordial leads, right axis deviation, secondary ST-T–wave abnormalities specific for age, and presence of Q waves.
Biventricular hypertrophy is suggested by the presence of criteria for both LVH and RVH. Right axis deviation in presence of LVH and combined tall R waves and deep S waves in the midprecordial leads greater than 60 mm (Katz-Wachtel criteria, see Fig. 1 ) suggest biventricular hypertrophy.
Abnormal P waves are usually referred to as right or left atrial abnormality. The ECG criteria for atrial abnormality are highly specific but insensitive when compared with cardiac magnetic resonance imaging (MRI). Left atrial abnormality is suggested by P wave duration 120 milliseconds or greater, widely notched P wave 40 milliseconds or greater, and left axis deviation of the terminal P wave between –30 and –90°. Right atrial abnormality is manifested as an increase in amplitude of the P wave, a rightward shift of the P wave vector, and prominent initial positivity of the P wave in V1 or V2 of 1.5 mm or greater.
Because the sensitivity of ECG criteria for chamber hypertrophy in pediatrics is low, it is used only as a screening tool and is correlated with other measurements for the assessment of hypertrophy or chamber enlargement. Because the sensitivity and specificity of individual criteria are low, further evaluation is usually based on presence of more than 1 criterion and clinical suspicion. Further evaluation is usually in the form of detailed personal and family history, physical examination, and echocardiogram.
Axis Deviation
The QRS axis is defined as the average direction in which the excitatory process spreads throughout the ventricular myocardium. A similar vector can be obtained for the P and the T waves. The normal QRS axis is age dependent. The QRS axis is rightward at birth and progressively shifts leftward to reach the normal adult range of 0° to 90° by 8 years of age. Thereafter, the shift remains stable, with further shifts dependent on conduction tissue abnormality seen in the older age. An abnormal QRS axis is not a specific finding. However, it should prompt a detailed history, physical examination, detailed evaluation of the ECG, and possibly an echocardiogram. About 15% of individuals among all age groups have rightward QRS frontal plane axis (>90°). About 8.7% of normal children have QRS axis leftward of 30°, and 1.8% have QRS axis leftward of 0°.
Persistence of rightward axis or right axis deviation in teenagers ( Box 4 ) may need further evaluation. Left axis deviation in teenagers can occasionally be seen as a normal variant but needs further evaluation in the form of an echocardiogram to rule out other possible causes ( Box 5 ).
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Normal variant, inherited as autosomal-dominant trait
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Tall asthenic individuals
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Dextrocardia
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Right ventricular hypertrophy
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Pulmonary causes
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Wolff-Parkinson-White syndrome
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Atrial septal defects
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Normal variant
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LBBB or LAHB
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Left ventricular hypertrophy
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Wolff-Parkinson-White syndrome
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Congenital heart defects
Endocardial cushion defect
Tricuspid atresia
Congenitally corrected transposition of the great arteries
Single ventricle
Double-outlet right ventricle with infracristal ventricular septal defect
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Mechanical factors: obesity, chest wall deformities, ascites, pregnancy
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