Researchers have developed the first validated risk stratification model for sudden cardiac death (SCD) in childhood hypertrophic cardiomyopathy (HCM) and published their research results in JAMA Cardiology.
To develop and validate a pediatric risk prediction model for SCD in childhood HCM, researchers collected data from a retrospective, multicenter, longitudinal cohort study to develop a prognostic model to identify patients at highest risk.
Patients in the study cohort were between 1 and 16 years old, consecutively evaluated at 39 centers in 17 countries between January 1970 and December 2017. The investigators defined HCM as “left ventricular wall thickness [>2] standard deviations above the body surface area-corrected population mean.”
In total, the cohort included 1024 patients with a median age of 11 (interquartile range 7-14) years; 68.3% were boys. Of the cohort, 53.1% of patients had a family history of HCM.
The follow-up period included 5984 patient-years (median, 5.3 years [interquartile range 2.6-8.3]). During that time, 7.5% of patients underwent a myectomy, 4.2% required a permanent pacemaker, 2.1% underwent cardiac transplantation, and 26.1% received an implantable cardioverter defibrillator (ICD) for primary or secondary prevention of SCD (91.4% and 8.6%, respectively).
Ultimately, 5.2% of patients in the cohort died: 56.6% because of SCD, 17% related to heart failure, 11.3% resulting from other cardiovascular reasons, 3.8% owing to non-cardiovascular reasons, and 5.7% from unknown causes. The annual mortality rate in the cohort was 0.89 (95% CI, 0.68-1.16).
Investigators used follow-up data, including all events that occurred during follow-up, to develop the risk model. Preselected variables included unexplained syncope, nonsustained ventricular tachycardia, left atrium diameter z score, maximal wall thickness z score, and left ventricular outflow tract gradient. Complete data for these variables were available from 51.5% of patients.
Investigators assessed 5-year risk prediction using 1029 patients with 58 events. The C index was 0.69 (95% CI, 0.66-0.72), and the calibration slope was 0.98 (95% CI, 0.59-1.38). Researchers assessed the clinical implications of the prediction model in 527 patients with 34 SCD endpoints and found that 1.7% of patients with a predicted risk <4%, 5% of patients with a predicted risk of 4%-<6%, and 10.4% of patients with a predicted risk ≥6% reached SCD.
“For every 10 [ICDs] implanted in patients with [≥]6% of a 5-year SCD risk, [one] patient may potentially be saved from SCD at 5 years,” the researchers wrote.
Study limitations included the “inherent problems” associated with retrospective studies, including missing data. In particular, patients with missing data primarily had milder disease; therefore, the results are biased toward patients with more severe disease.
“External validation studies are now required to demonstrate the accuracy of this model’s predictions in diverse patient populations,” the researchers concluded. “Consensus opinion of experts will be required to determine whether absolute thresholds for ICD recommendations are needed.”
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Norrish G, Ding T, Field E, et al. Development of a novel risk prediction model for sudden cardiac death in childhood hypertrophic cardiomyopathy (HCM Risk-Kids) [published online August 14, 2019]. JAMA Cardiol. doi: 10.1001/jamacardio.2019.2861