Jack Salerno, MD, Physiologic ECG Variants in the Pediatric Athlete Heart Rate, Rhythm, and Juvenil

Summary

This lecture on pediatric electrocardiograms (ECGs) explores the similarities and differences between pediatric and adult ECGs. Key points include the significance of age-related changes, heart rate, T-wave patterns, and RV dominance in children. The lecture highlights how ECG characteristics evolve from birth to adolescence, with particular focus on T-wave inversions and juvenile T-wave patterns. It emphasizes the importance of understanding these age-dependent changes to accurately interpret pediatric ECGs, particularly for athletes. By age 16, T-wave inversions beyond certain leads are considered abnormal, requiring further evaluation.

Takeaways

• 😀 The basic principles of ECG are the same in pediatric and adult patients, with some key differences in heart rate, P wave duration, and sampling rates.
• 😀 The P wave amplitude remains consistent throughout life, from birth to death.
• 😀 Right ventricle (RV) dominance is present at birth, contributing significantly to cardiac output, and decreases as the left ventricle (LV) becomes more dominant with age.
• 😀 The mean axis is rightward at birth (130 degrees) and gradually shifts towards the adult pattern (around 1 year of age).
• 😀 In the first months of life, the QRS complex changes with decreasing RV dominance, ultimately resembling adult patterns by about 4 years of age.
• 😀 T-wave patterns evolve over time; at birth, they are upright in right-sided leads, and by one week of age, they become negative before eventually resembling adult patterns by around 12 years old.
• 😀 T-wave inversion in right-sided leads is normal for children under 16, specifically in the juvenile T-wave pattern, and does not indicate pathology in most cases.
• 😀 T-wave inversion beyond V2 in children younger than 16 is typically normal, but after 16 years, such inversions in anterior leads require further evaluation for possible pathology.
• 😀 The fastest heart rates in life occur between one to two months of age, gradually slowing as children grow.
• 😀 Age-based criteria are essential for interpreting pediatric ECGs, as there are significant differences across age groups in heart rate, intervals, axis, and voltage.

Q & A

What are the main similarities between pediatric and adult ECGs?

The basic principles of electrocardiography (ECG) are identical for both pediatric and adult populations. Both have sinus rhythm and P wave amplitude that remains consistent from birth to death.

What are some key differences in pediatric ECG compared to adults?

Key differences in pediatric ECGs include variations in heart rate, P wave duration, amplitude, vectors, and technological aspects like ECG sampling rate and bandwidth.

How does exercise affect the pediatric ECG?

Exercise-induced physiologic changes in children mirror those in adults. For instance, athletes tend to have larger left ventricular (LV) wall thickness and chamber dimensions. Factors such as age, sex, ethnicity, and sport type influence cardiac remodeling.

What is the purpose of the 'Davignon data set' in pediatric ECG interpretation?

The Davignon data set, established in 1979, provides age-related ECG criteria for children, primarily based on a small, Caucasian population. It offers reference values for interpreting pediatric ECGs, although newer data from the Pediatric Heart Network will likely lead to changes in these values.

What significant physiologic change happens in the RV and LV during early childhood?

At birth, the right ventricle (RV) is dominant and handles a larger portion of the cardiac output (60-65%) compared to the left ventricle (LV). Over time, the RV dominance regresses, and the LV increases in dominance, which influences the child’s ECG patterns.

At what age does the pediatric ECG axis resemble that of adults?

The pediatric ECG axis begins to resemble the adult pattern by about one year of age, as the LV becomes more dominant and the RV dominance decreases.

What happens to the QRS complex as the child grows?

At birth, the QRS complex is influenced by RV dominance, with a prominent R wave in lead V1. As the child ages, the RV dominance decreases, and the QRS complex shifts, with smaller R waves in V1 and larger R waves in leads V5 and V6, typical of adult patterns by around four years of age.

How do T waves change in pediatric patients as they grow?

At birth, T waves are upright in the right-sided leads. By one week of age, they become negative in these leads. Over time, they progressively resemble adult T wave patterns, with positive T waves in right precordial leads by the time the child reaches puberty.

When do T waves in pediatric patients resemble those of adults?

By around age 16, T waves in pediatric patients resemble those of adults, with T wave inversions beyond lead V2 becoming abnormal and signaling the need for further evaluation.

What is the 'juvenile T wave pattern' and when is it considered normal?

The 'juvenile T wave pattern' refers to T wave inversions in the right precordial leads, which is considered normal in children younger than 16 years. However, if T wave inversions persist in older adolescents or adults, it may suggest pathology and warrant further evaluation.