Late gadolinium enhancement (LGE) was a risk factor for sudden cardiac death (SCD) in children and adolescents with hypertrophic cardiomyopathy (HCM), in a new international retrospective cohort study. The findings should be considered in clinical evaluation for pediatric HCM patients, in whom the ability to predict SCD risk is “currently inadequate,” according to the study’s authors, led by Raymond H. Chan, MD, from Toronto General Hospital, Canada. The study was published Wednesday online ahead of the 25 September issue of the Journal of the American College of Cardiology. While predictive measures have remained poor for children, LGE as determined by cardiovascular magnetic resonance imaging has been associated with SCD events in adults with HCM, the authors noted. HCM is the most common genetically determined cardiomyopathy and is the leading cause of SCD in children and adolescents, according to the authors. Implantable cardiac defibrillators (ICD) are the “only effective treatment of life-threatening arrythmias,” the authors added, however, they stressed that the advantages are offset by substantial associated morbidity rates, “particularly in younger patients.” “Inappropriate ICD shocks occur in up to 6.5% of children annually, among other complications,” they added. “The overall goal must be to implant ICDs only in patients at the highest risk for SCD. Despite available prognostication tools, the ability to identify these patients, while avoiding ICD implants in patients unlikely to experience SCD, remains insufficient.” Study design The current study therefore set out to test whether LGE could be a reliable predictor of SCD in paediatric HCM patients. The study ran in 700 HCM patients younger than 21 years who had undergone cardiac magnetic resonance (CMR) imaging in one of 37 centres across the U.S., Europe and South America between April 2015 and September 2022. The primary outcome was SCD and surrogate events, including resuscitated cardiac arrest and appropriate discharges from an implantable defibrillator. Demographic, electrocardiographic, echocardiographic, clinical and genetic information was collected from patients’ medical records. Age at diagnosis was a median of 12 years (interquartile range [IQR]: 7 to 15 years), the median age at CMR was 14.8 years (IQR: 11.9 to 17.4 years) and 74% were male. The most common initial reason for referral was dyspnea or murmur (40.3%), followed by family history or screening (32.7%) and chest pain (11.6%). Left ventricular outflow tract (LVOT) obstruction with a gradient of 30 mm Hg or higher was seen in 170 children (24.3%). LGE was seen in 233 of the 700 patients (33.3%, a mean burden of 5.9% of left ventricular myocardium), and these patients tended to be older. There was a correlation between LGE and the amount of LGE and age (0.15% increase in LGE percentage per year; P < 0.001), higher left ventricular (LV) mass (0.15% LGE per 10g LV mass or 0.28% LGE per 10 g/m2 LV mass; P < .001), maximal wall thickness (0.23% LGE per mm or 0.24 LGE per z score point) and a larger left atrium diameter r (0.12% LGE per mm or 0.45% per z score point; P < .001). Patients with higher LGE burden also had lower LVEF (−0.54% per 1% LGE; P < .001). LGE as a predictor of SCD Patients with 10% or more LGE, relative to total myocardium, had a higher risk of SCD (unadjusted hazard ratio [HR]: 2.19; 95% confidence interval [CI]: 1.59-3.02; P < .001). A total 35 patients (5%) experienced SCD (3 patients) or an equivalent endpoint at a mean age of 14.8 years (IQR: 6.3 to 27). Equivalent endpoints experienced included 20 patients with resuscitated arrest, and 14 with appropriate ICD shock. Three patients experienced more than one event. Furthermore, the addition of LGE burden improved the performance of existing risk scoring tools for SCD in childhood – namely the HCM Risk-Kids score (before LGE addition: 0.66; 95% CI, 0.58-0.75; after LGE addition: 0.73; 95% CI, 0.66-0.81) and the Precision Medicine in Cardiomyopathy score (before LGE addition: 0.68; 95% CI, 0.49-0.77; after LGE addition: 0.73; 95% CI, 0.64-0.82). “These results, which need to be confirmed in independent cohorts, suggest that quantitative measure of LGE can become part of a comprehensive approach to identify patients at highest risk of SCD,” said the researchers. “Future work is needed to demonstrate how to use LGE in a risk score that includes other risk factors.” Source: Chan RH, van der Wal L, Liberato G, et al. Myocardial Scarring and Sudden Cardiac Death in Young Patients With Hypertrophic Cardiomyopathy: A Multicenter Cohort Study. JAMA Cardiol 2024; DOI: 10.1001/jamacardio.2024.2824. Image Credit: Nina Lawrenson/peopleimages.com - stock.adobe.com