Introduction: The ECG is a useful cardiac diagnostic and screening tool, but current utility is limited by absence of reliable normal reference values across all age, sex, and race categories.
Hypothesis: Contemporary ECG measurements in children from North America vary by sex and race and differ from norms commonly used in practice.
Methods: Digital 12-lead ECGs were retrospectively collected from healthy children ≤18 years who simultaneously had a normal echo at 19 centers in the PHN. The indication for studies was not collected. Exclusion criteria were cardiac or systemic disease or family history of cardiomyopathy. Patients were classified into 36 study groups: 6 age (<1 month; 1 month - <3 years; 3 - <6 years; 6 - <12 years; 12 - <16 years; 16-18 years), 2 sex, and 3 race (white, African-American, and other/mixed). Among other parameters the R wave amplitude in V6 was measured; mean±SD were determined by sex and race for each age group. Multivariate analysis, stratified by age group, was conducted using race, sex, and the race*sex interaction term as predictors. For comparison to the landmark study by Davignon (1979) (DAV), subjects were reclassified to similar age groups and analyzed by a one-sample t-test.
Results: Among 2400 ECGs, small but significant differences were found in the mean R wave amplitude in V6 for many age categories with males > females, African-Americans > white and other race, and PHN > DAV for both sexes (Table). This was more dramatic for the 98%ile where differences of up to 677microV were observed.
Conclusions: In this large, diverse cohort of healthy children from North America the mean R wave amplitude in V6 varied by sex and race. In addition, the mean R wave amplitude in V6 was greater than the normal ECG data set published by DAV. These differences in both the mean and 98 percentile values have important clinical implications for the interpretation of pediatric ECGs when used for diagnosis or screening, including thresholds for left ventricular hypertrophy.