The role of the electrocardiographic phenotype in risk stratification for sudden cardiac death in childhood hypertrophic cardiomyopathy

Abstract

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.

Childhood Hypertrophic Cardiomyopathy: A Disease of the Cardiac Sarcomere

“…12 lead ECG Proposed 12 lead ECG features include; measures of LV hypertrophy (82) and abnormal repolarisation (83). An ECG risk score has been developed by Ostman-Smith et al (83) but this was shown to have only moderate discriminatory ability in an external validation study (84).…”

Age-Related Electrocardiographic Characteristics of Male Junior Soccer Athletes

“…Consequently, improved screening techniques for detecting are strongly required in the clinical arena (28). Recently a large, multicenter study in childhood hypertrophic cardiomyopathy demonstrated that ECG abnormalities were common and varied, but none of them, either in isolation or in the ECG risk score, were associated with the 5-year sudden cardiac death risk (29). Potentially, other individual ECG parameters may improve the current risk prediction models.…”

What Aspects of Phenotype Determine Risk for Sudden Cardiac Death in Pediatric Hypertrophic Cardiomyopathy?

“…Studies in the sub-set of the study population for HCMRisk-Kids with ECGs archived found a cut-off of >5 points only modestly predictive for a wider end-point of “freedom from major arrhythmia in the next five years” over a short follow-up of only 3.9 yrs. However, when the total ECG point-score was used, the study found a hazard ratio of 1.11 per point, higher than the hazard ratio for the LA Z-score of 1.03 in the same population [ 59 ]. A recent external validation of the ECG risk score cut-off >5 points in a tertiary centre childhood-HCM study group from Toronto, with a mean follow-up of 14.6 y, found a sensitivity of 95% and specificity of 56% for SCD in the first 5 years of follow-up [ 64 ].…”

“…A recent external validation of the ECG risk score cut-off >5 points in a tertiary centre childhood-HCM study group from Toronto, with a mean follow-up of 14.6 y, found a sensitivity of 95% and specificity of 56% for SCD in the first 5 years of follow-up [ 64 ]. All the above studies find very high negative predictive values for cut-off >5 points, between 97–100% [ 19 , 59 , 65 , 66 ]. QTC dispersion is an additional ECG feature that has been reported to have a significant correlation with SCD in childhood-HCM, with a hazard ratio of 1.6 per 20 ms increase [ 22 ], or a cut-off of 0.055 being associated with arrhythmic end-point [ 26 ].…”

“…A more recent and larger study of a national cohort of pediatric HCM-patients showed that ST-depression ≥2 mm already at rest, not common in childhood-HCM, was present in 43.5% of patients with sudden cardiac death or cardiac arrest, and only in 8.4% of patients without arrhythmia events ( p < 0.0001) [ 19 ]. ST-depression at rest may be more common in a tertiary centre population, where it was reported to occur in 16% of patients without arrhythmia events [ 59 ]. ST-depression during exercise testing conferred a relative risk of 5.7 [95%CI 1.9–17.4; p = 0.0035] of sudden death or cardiac arrest, with a positive predictive value of 56% and a specificity of 83% [ 19 ].…”