Objective To establish which risk factors are predictive for sudden death in hypertrophic cardiomyopathy (HCM) diagnosed in childhood.
Methods A Swedish national cohort of patients with HCM diagnosed <19 years of age was collected between 1972 and 2014, consisting of 155 patients with available ECGs, with average follow-up of 10.9±(SD 9.0) years, out of whom 32 had suffered sudden death or cardiac arrest (SD/CA group). Previously proposed risk factors and clinical features, ECG and ultrasound measures were compared between SD/CA group and patients surviving >2 years (n=100), and features significantly more common in SD/CA group were further analysed with univariate and multivariate Cox hazard regression in the total cohort.
Results Ranked according to relative risk (RR) the ECG risk score >5 points had an RR of 46.5 (95% CI 6.6 to 331), sensitivity of 97% (83% to 100%) and specificity of 80% (71% to 88%) (p<0.0001), and was the best ECG predictor, predicting a 5-year risk of SD/CA of 30.6%. The following are other features with importantly raised RR: Detroit wall thickness Z-score >4.5: 9.9 (3.1 to 31.2); septal thickness ≥190% of upper limit of normal for age (septum in % of 95th centile for age (SEPPER) ≥190%): 7.9 (3.2 to 19.4); ventricular tachycardia: 9.1 (3.6 to 22.8); ventricular ectopics on exercise testing: 7.4 (2.7 to 20.2); and left ventricular outflow gradient (left ventricular outflow tract obstruction (LVOTO)) >50 mm Hg: 6.6 (4.0 to 11.0). Family history was non-significant. Multivariate Cox hazard analysis gives the following as early predictors: limb-lead QRS amplitude sum (p=0.020), SEPPER ≥190% (p<0.001) and LVOTO at rest (p=0.054); and for late predictors: last ECG risk score (p=0.002) and last Detroit Z-score (p=0.001). Both early (p=0.028) and late (p=0.037) beta-blocker doses reduced risk in the models.
Conclusions ECG phenotype as assessed by ECG risk score is important for risk of sudden death and should be considered for inclusion in risk stratification of paediatric patients with HCM.
- sudden cardiac death
- paediatric arrythmias
- risk factors
- cardiomyopathy hypertrophic
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Contributors Study conception and design: IÖ-S. Acquisition of data: IÖ-S, GS, AR, PL, EF. Analysis and interpretation of data: IÖ-S, EF. Drafting of manuscript: IÖ-S. Critical revision: IÖ-S, GS, AR, PL, EF.
Funding The study was supported by grants from the Swedish Heart and Lung Foundation (Number 20080510), and by Gothenburg University ALF project grant (ALFgbg-544981).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Detailed data on type of pharmacotherapy and dose are available to share with any collaborative studies studying relationship between pharmacotherapy and outcome.