Prevalence, risk factors and outcomes of QT prolongation in primary and Rasopathy-associated hypertrophic cardiomyopathy.

Abstract

Background: The clinical significance of QT prolongation in pediatric hypertrophic cardiomyopathy (HCM) is unclear.

Objective: Determine the prevalence, risk factors and outcomes of QT prolongation in pediatric HCM patients.

Methods: Phenotype-positive, pediatric primary HCM (P-HCM) (n=212) and RASopathy (RAS-HCM) patients (n=55) were included. Corrected JT interval (JTc) as a measure of QT prolongation was calculated at baseline and last follow-up. Factors associated with JTc duration were analyzed using generalized estimating equation model. Association of JTc prolongation (JTc >370 ms) with risk of sudden cardiac death (SCD) events was analyzed. SCD events were defined as a composite of SCD, resuscitated SCD event, or appropriate shock from a primary prevention ICD.

Results: Twenty-four% P-HCM and 44% RAS-HCM patients had prolonged JTc (p=0.004). JTc had only a modest correlation with severity of LV hypertrophy. In P-HCM, JTc prolongation was associated with SCD events on multivariable analysis [hazard ratio 2.9 (1.2-6.8), p=0.016]. 5-year SCD event-free survival from baseline evaluation was 86% in P-HCM. Including JTc as a risk factor improved the c-statistic for 5-year SCD risk prediction to 0.85 compared to 0.73 when using PRIMaCY risk scores alone, and to 0.73 compared to 0.70 when using HCM RiskKids scores alone.

Conclusion: JTc prolongation was independently associated with risk of SCD events. Including JTc prolongation with SCD risk scores improved 5-year SCD risk prediction for P-HCM. This has implications for closer SCD risk monitoring in P-HCM patients with JTc prolongation.