New Risk Prediction Model for SCD in Childhood Hypertrophic Cardiomyopathy

Study Questions:

Can a new clinical risk tool predict sudden cardiac death (SCD) in children with hypertrophic cardiomyopathy (HCM)?

Methods:

The model was developed from a retrospective, multicenter, international, longitudinal cohort study of 1,024 consecutive patients over a 17-year period. Patients were ≤16 years old. The primary study endpoint was the composite outcome of SCD or an “equivalent event” such as sustained ventricular tachycardia (VT) associated with hemodynamic compromise, appropriate implantable cardioverter-defibrillator (ICD) therapy, or aborted cardiac arrest. Potential predictor variables must have been the subject of >2 published studies and independently associated with SCD. Internal validation of the model was performed via resampling, C index (concordance), and calibration.

Results:

Median age was 11 years; 699 (68.3%) were boys; family history was present in approximately 53%; median follow-up was 5.3 years; 267 (26.1%) received an ICD (244 for primary prevention); 89 had SCD or “equivalent event” within 5 years (39 SCD); patient characteristics significantly associated with SCD were New York Heart Association class II or higher, unexplained syncope, nonsustained VT, maximal wall thickness (MWT), and left atrial (LA) diameter. Variables to develop the risk model were unexplained syncope, nonsustained VT, LA diameter z score, MWT z score, and left ventricular outflow tract (LVOT) gradient. Complete data were available for 527 (51.5%) and 34 of the SCD patients; using a 5-year risk of SCD of ≥4% to recommend a primary prevention ICD would identify 31 (91.2%) SCDs or “equivalent events.” One patient may be saved from SCD at 5 years for every 10 ICDs implanted in those with SCD ≥6%.

Conclusions:

This novel risk model for SCD in pediatric patients with HCM can estimate risk at 5 years and guide discussions regarding ICD implantation.

Perspective:

  1. The five risk predictors chosen were unexplained syncope, nonsustained VT, LA diameter z score, MWT z score, and LVOT gradient.
  2. Age and family history of SCD were potential predictor variables that were not chosen based on current data; in fact, including them (as well as heart failure symptoms) did not improve the risk model’s performance.
  3. Gene mutation status and late gadolinium enhancement on cardiac magnetic resonance imaging were also not included but will be important enhancements in future risk models.
  4. Limitations include missing data in almost half of subjects, only 5.3 years (median) of follow-up, no external validation, and MWT z score likely influenced by time point of disease expression.
  5. Variable phenotypic expression of HCM poses significant challenges to risk assessment in the young. Thus, shared decision making is essential when determining who should receive an ICD for primary prevention of SCD. The new risk model in this study is a potentially important new tool for risk assessment, but external validation and refinements are needed.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Sports and Exercise Cardiology, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Magnetic Resonance Imaging, Sports and Exercise and Imaging

Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Cardiomyopathy, Hypertrophic, Death, Sudden, Cardiac, Defibrillators, Implantable, Gadolinium, Heart Failure, Hemodynamics, Magnetic Resonance Imaging, Mutation, Pediatrics, Primary Prevention, Risk Assessment, Syncope, Tachycardia, Ventricular, Sports


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