AIMS: The 12-lead electrocardiogram (ECG) is routinely performed in children with hypertrophic cardiomyopathy (HCM). An ECG risk score has been suggested as a useful tool for risk stratification, but this has not been independently validated. This aim of this study was to describe the ECG phenotype of childhood HCM in a large, international, multi-centre cohort and investigate its role in risk prediction for arrhythmic events. METHODS AND RESULTS: Data from 356 childhood HCM patients with a mean age of 10.1 years (±4.5) were collected from a retrospective, multi-centre international cohort. Three hundred and forty-seven (97.5%) patients had ECG abnormalities at baseline, most commonly repolarization abnormalities (n = 277, 77.8%); left ventricular hypertrophy (n = 240, 67.7%); abnormal QRS axis (n = 126, 35.4%); or QT prolongation (n = 131, 36.8%). Over a median follow-up of 3.9 years (interquartile range 2.0-7.7), 25 (7%) had an arrhythmic event, with an overall annual event rate of 1.38 (95% CI 0.93-2.04). No ECG variables were associated with 5-year arrhythmic event on univariable or multivariable analysis. The ECG risk score threshold of >5 had modest discriminatory ability [C-index 0.60 (95% CI 0.484-0.715)], with corresponding negative and positive predictive values of 96.7% and 6.7. CONCLUSION: In a large, international, multi-centre cohort of childhood HCM, ECG abnormalities were common and varied. No ECG characteristic, either in isolation or combined in the previously described ECG risk score, was associated with 5-year sudden cardiac death risk. This suggests that the role of baseline ECG phenotype in improving risk stratification in childhood HCM is limited.

Alder Hey Children's hospital Liverpool UK

Arrhythmia and Inherited Cardiac Diseases Unit Hospital Sant Joan de Déu University of Barcelona Spain

Bambino Gesu Hospital Rome Italy

Cardiology Unit A Meyer Pediatric Hospital Florence Italy

Careggi University Hospital Florence Italy

Centre for Inherited Cardiovascular Diseases Great Ormond Street Hospital Great Ormond Street London WC1N 3JH UK

Complexo Hospitalario Universitario A Coruña CIBERCV A Coruña Spain

Department of cardiology Aarhus University Hospital Aarhus Denmark

Department of Cardiology and Geriatrics Kochi Medical School Kochi University Japan

Department of Cardiology The Children's Memorial Health Institute Warsaw Poland

Department of Statistical Science University College London London UK

Favaloro Foundation University Hospital Buenos Aires Argentina

Hospital General Universitario Gregorio Marañón Madrid Spain

Hospital Universitario Puerta de Hierro Majadahonda CIBERCV Madrid Spain

Institute of Cardiovascular Sciences University College London London UK

John Radcliffe Hospital Oxford UK

Leiden University Medical Center Leiden Netherlands

Medical Sciences Department School of Medicine University of Girona

Odense University Hospital Odense Denmark

Onassis Cardiac Surgery Center Athens Greece

Our Lady's Children's Hospital Dublin Ireland

Papa Giovanni XXIII hospital Bergamo Italy

Royal Brompton and Harefield NHS Trust London UK

Royal Hospital for Children Glasgow UK

S Orsola Malpighi Hospital Bologna Italy

Southampton general Hospital Southampton UK

St Bartholomew's Centre for Inherited Cardiovascular Diseases St Bartholomew's Hospital West Smithfield London UK

The Freeman Hospital Newcastle UK

The Murdoch Children's Research Institute

The Royal Children's Hospital Melbourne Australia

University Francisco de Vitoria Pozuelo de Alarcon Spain

University Hospital Motol Prague Czech Republic

University Hospital of Wales Cardiff UK

University Hospital Virgen de la Arrixaca Murcia Spain

University of Melbourne Australia

Val d'Hebron University Hospital Barcelona Spain

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