Long-term Outcome and Prognostic Determinants in Children with Hypertrophic Cardiomyopathy

Objectives: We sought to determine clinical, angiographic, and echocardiographic predictors of survival in children with isolated hypertrophic cardiomyopathy (HCM) in a large pediatric centre.

Background: Sudden death is a catastrophic outcome of HCM in childhood but has been difficult to predict. Current therapies might provide for improved outcome if factors identifying high risk can be identified.

Methods: Records of 99 patients diagnosed with HCM from 1958 to 1997 at <18 yr were reviewed for clinical, angiographic (n = 62) and echocardiographic (n = 83) predictors of survival outcome. The effects of clinical characteristics on sudden death (including resuscitated sudden death) were individually tested in Cox's proportionate hazard modeling.

Results: Seventy-one subjects were male. Median age at diagnosis was 5.0 yr with a medical follow-up interval of 4.8 yr. Thirty-seven of 97 patients had a family history of HCM. Ambulatory electrocardiograms (ECG) in 78 patients demonstrated supraventricular tachycardia in 16 and ventricular tachycardia in 21. Death or resuscitated sudden death occurred in 18 patients. Sudden death rate was 2.7%/yr after age 8 yr. Cox's proportionate survival modeling revealed increased corrected QT interval (QTc) dispersion on ECG (relative risk [RR] 1.61 per 20 ms increment, p < 0.0003), ventricular tachycardia (VT) on ambulatory ECG (RR 3.75, p < 0.006) and myocardial bridging of the LAD coronary (RR 12.0, p < 0.003) to be associated with reduced time to death or resuscitated sudden death.

Conclusions: Detailed assessment of ECGs, ambulatory ECGs, and coronary angiography can assist in identifying which children with HCM are at risk for sudden death.