{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"medRxiv"}],"indexed":{"date-parts":[[2026,2,11]],"date-time":"2026-02-11T17:04:24Z","timestamp":1770829464784,"version":"3.50.1"},"posted":{"date-parts":[[2026,2,9]]},"group-title":"Cardiovascular Medicine","reference-count":36,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,2,9]],"date-time":"2026-02-09T00:00:00Z","timestamp":1770595200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,2,9]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                <jats:sec>\n                  <jats:title>Background<\/jats:title>\n                  <jats:p>Normative pediatric electrocardiographic (ECG) parameters are standardized, but lack temporal resolution for neonates and infants. These values are clinically important, as they support the diagnosis, risk stratification, and management of cardiovascular diseases (CVD).<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>Five ECG parameters (heart rate (HR), QRS, PR, QT, QTc intervals) were retrospectively analyzed from 7,346 recordings from 6,967 patients at a large pediatric hospital. Patients were only included if their ECG was adjudicated as normal by a pediatric cardiologist. Patients were assigned to 45 age groups: neonates (1-35 days, 35 groups), infants (2-6 months, 5 groups), and young children (1-5 years, 5 groups). Sensitivity analysis ranked ECG parameters to determine those most affected by age. Z-scores were used to quantify deviations in developmental ECG parameter trajectories in CVD-free patients compared with unrepaired tetralogy of Fallot (TOF, n=305).<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>Developmental shifts in ECGs were observed for all patients, irrespective of whether intensive care unit or CVD patients were included in the analysis. All five ECG parameters differed significantly between early (1-8 days) and late neonates (9-35 days). Sensitivity analysis revealed rapid ECG parameter adaptations during the neonatal stage, with slower changes during infancy and early childhood. Unrepaired TOF patients had significantly different HR, PR, and QRS values in the late neonatal group compared with CVD-free children. Z-scores revealed disease-specific deviations (\u2265 2 SD of baseline), including outlier QTc values in 32.7% and 24.3% of early and late neonatal TOF patients, respectively.<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Conclusion<\/jats:title>\n                  <jats:p>This study defined the values of five key ECG parameters, with enhanced age-specific resolution in neonates, infants, and children. Neonatal age emerged as the most dynamic stage for ECG parameter changes. This study demonstrated that high temporal resolution of age-specific ECG parameters can identify abnormal deviations, which can provide valuable insight for the diagnosis and management of CVD in early life.<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>CLINICAL PERSPECTIVE<\/jats:title>\n                  <jats:sec>\n                    <jats:title>What is known<\/jats:title>\n                    <jats:list list-type=\"bullet\">\n                      <jats:list-item>\n                        <jats:p>Normative pediatric ECG values derived from healthy children have been reported; however, available reference datasets are often limited by broad age stratification, particularly during the neonatal and infant periods.<\/jats:p>\n                      <\/jats:list-item>\n                    <\/jats:list>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>What the study adds<\/jats:title>\n                    <jats:list list-type=\"bullet\">\n                      <jats:list-item>\n                        <jats:p>High-temporal-resolution reference values are reported for five clinically relevant ECG parameters, with day-level resolution in neonates and month-level resolution in infants.<\/jats:p>\n                      <\/jats:list-item>\n                      <jats:list-item>\n                        <jats:p>Retrospective ECG data from a CVD-free pediatric cohort closely align with values reported in healthy pediatric populations, supporting their use as surrogate baseline reference data.<\/jats:p>\n                      <\/jats:list-item>\n                      <jats:list-item>\n                        <jats:p>Postnatal ECG developmental trajectories are preserved in CVD-free pediatric patients but deviate in disease states such as unrepaired tetralogy of Fallot, highlighting the potential clinical utility of these reference trajectories for identifying disease-related alterations.<\/jats:p>\n                      <\/jats:list-item>\n                    <\/jats:list>\n                  <\/jats:sec>\n                <\/jats:sec>","DOI":"10.64898\/2026.02.07.26345587","type":"posted-content","created":{"date-parts":[[2026,2,10]],"date-time":"2026-02-10T02:30:26Z","timestamp":1770690626000},"source":"Crossref","is-referenced-by-count":0,"title":["Age-dependent Dynamics of the Electrocardiographic Parameters in Cardiovascular Disease-Free Children"],"prefix":"10.64898","author":[{"given":"Kazi T.","family":"Haq","sequence":"first","affiliation":[{"name":"Sheikh Zayed Institute for Pediatric Surgical Innovation, Children\u2019s National Hospital, Washington, DC"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kathleen","family":"McLean","sequence":"additional","affiliation":[{"name":"Sheikh Zayed Institute for Pediatric Surgical Innovation, Children\u2019s National Hospital, Washington, DC"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Charles I.","family":"Berul","sequence":"additional","affiliation":[{"name":"Sheikh Zayed Institute for Pediatric Surgical Innovation, Children\u2019s National Hospital, Washington, DC"},{"name":"Division of Cardiology, Children\u2019s National Hospital, Washington, DC"},{"name":"Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3880-7200","authenticated-orcid":false,"given":"Nikki Gillum","family":"Posnack","sequence":"additional","affiliation":[{"name":"Sheikh Zayed Institute for Pediatric Surgical Innovation, Children\u2019s National Hospital, Washington, DC"},{"name":"Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC"},{"name":"Department of Pharmacology and Physiology, The George Washington University School of Medicine and Health Sciences, Washington, DC"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"54368","reference":[{"key":"2026021108050876000_2026.02.07.26345587v1.1","doi-asserted-by":"crossref","first-page":"769","DOI":"10.1016\/j.clp.2012.09.009","article-title":"Physiology of transition from intrauterine to extrauterine life","volume":"39","year":"2012","journal-title":"Clin. 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