A 13-year-old competitive swimmer walks into my clinic for a pre-participation screen. Her ECG shows T-wave inversions across the anterior chest leads. In an adult athlete, that would be a red flag. In her, it is almost certainly normal. Knowing the difference is the whole point and for years, cardiologists reading ECGs in young athletes have had to rely on criteria designed for adults and adapt them by instinct and experience.

One of the most practically useful contributions of the new ESC and AEPC consensus statement on cardiac screening in paediatric athletes is a set of dedicated ECG criteria for children under 16. These criteria define, for the first time in a joint European consensus document, what counts as normal, borderline, and abnormal in a young athlete's heart tracing. The difference from adult criteria is not cosmetic. It reflects fundamental biological differences between children and adults.

The most striking example is T-wave inversion in the anterior chest leads. In adults, T-wave inversion beyond V2 is classified as abnormal and triggers further investigation for cardiomyopathy. In children, this pattern, known as the juvenile T-wave pattern, is a well-recognised physiological finding, particularly before the pubertal growth spurt. The new guidance classifies T-wave inversion in V1 through V3 as normal in athletes under 16, and V1 through V4 as normal in athletes under 12. Applying adult rules to these children would generate a wave of false alarms, unnecessary investigations, and considerable anxiety for families.

The document goes further. Sinus bradycardia, incomplete right bundle branch block, increased QRS voltages, early repolarisation, first-degree heart block, and junctional rhythm are all designated as normal in paediatric athletes in the appropriate context. Children have lower chest wall impedance, faster-growing hearts, and autonomic nervous systems in a different state of maturity compared to adults. All of these influence what appears on the trace.

Borderline findings, those requiring clinical judgement rather than automatic escalation, include complete right bundle branch block, QTc prolongation to between 440 and 460 milliseconds in boys, and an axis deviation at the edges of normal range. These warrant a second look, but not necessarily alarm. Truly abnormal findings in a child athlete, warranting prompt further investigation, include T-wave inversion in lateral or inferior leads beyond V3, ST depression, pathological Q waves, a QTc above 460 milliseconds, signs of pre-excitation, or left bundle branch block.

The guidance also acknowledges a practical problem that any paediatrician will recognise. Cardiac disease in children often presents differently from its adult counterpart. Hypertrophic cardiomyopathy, arrhythmogenic cardiomyopathy, and channelopathies like Long QT syndrome may all produce subtle or atypical ECG changes in a child that would look more overt in an adult. The sensitivity of even the best ECG criteria is lower in younger adolescents. One study found sensitivity of around 57% in athletes aged 12 to 14, compared to over 97% in older adolescents. This is not a reason to abandon ECG screening. It is a reason to pair it with a careful history, a skilled examination, and appropriate follow-up.

What does this mean in the clinic? It means that reading an ECG in a 12-year-old athlete is a specialist skill. It requires knowing not just the criteria, but the biology behind them and understanding why a certain finding is age-appropriate. It also requires recognising when a borderline result deserves escalation, and communicating uncertainty to a family without causing disproportionate distress. The new criteria give us a framework. Clinical expertise gives us the judgement to use it well.

Author: Dr. Alessandro Giardini, MD, PhD, Consultant Paediatric Cardiologist

Written 03/06/2026