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for primary prevention ICD implantation in patients with a low or intermediate risk category.

7.1.5.5 Sarcomeric variants

A small number of studies have explored the prognostic value of sarcomeric variants in HCM. Despite initial attempts to classify variants as ‘malignant’ or ‘benign’,803–807 no studies have shown an independent role for specific sarcomeric variants in SCD risk prediction. Variants initially classified as ‘malignant’ or ‘benign’ can have very different phenotypic expression, even in members of the same family,808–810 and, as variants are often found in individual families, evaluation of their prognostic implications is problematic. Similarly, while the presence of multiple sarcomeric variants in an individual has been suggested to be associated with a worse prognosis,608,811–813 other cohorts have not consistently reported this association.807,814–816 Recent studies have evaluated the potential prognostic role of the presence of any sarcomeric variant. The largest of these, comprising 2763 patients, showed a statistically significant impact on overall prognosis in those with vs. without a sarcomeric variant, but did not assess its association specifically with SCD.238 A smaller study of 512 probands and 114 relatives, of whom 327 had a disease-causing sarcomeric variant, suggested that the presence of a pathogenic variant was independently associated with allcause, cardiovascular, and heart failure mortality as well as SCD/ aborted SCD (HR 2.88; 95% CI, 1.23–6.71).817 Patients with a sarcomeric variant were younger and were more likely to have NSVT, syncope, and LVOTO and the association with SCD lost statistical significance (HR 2.44; 95% CI, 0.99–6.01; P = 0.052) after adjusting for ≥2 major clinical risk factors. The role of sarcomeric variants as a predictor of SCD independent of SCD risk-prediction models (e.g. HCM Risk-SCD and HCM Risk-Kids) remains to be demonstrated. Based on the available data, the Task Force does not recommend the use of the presence of sarcomeric variant(s) to guide decisions around ICD implantation for primary prevention in individuals with a low or intermediate SCD risk score.

7.1.5.6 Prevention of sudden cardiac death

There are no randomized, controlled data to support the use of AADs for the prevention of SCD in HCM. Amiodarone was associated with a lower incidence of SCD in one small observational study of patients with non-sustained ventricular tachycardia (NSVT) on Holter monitoring, but observational data suggest that amiodarone often fails to prevent SCD.818,819 Disopyramide does not appear to have a significant impact on the risk of SCD.632 However, beta-blockers and/or amiodarone are recommended in patients with an ICD who continue to have symptomatic ventricular arrhythmias, paroxysmal AF, or recurrent shocks despite optimal treatment and device re-programming.820 There are no randomized trials or statistically validated prospective prediction models that can be used to guide ICD implantation in patients with HCM. Recommendations are instead based on observational, retrospective cohort studies that have determined the relationship between clinical characteristics and prognosis. The 2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy recommended a risk-prediction model—HCM Risk-SCD (https:// qxmd.com/calculate/calculator_303/hcm-risk-scd)—that provides individualized, quantitative risk estimates using an enhanced phenotypic approach.525 This approach has since been validated in independent cohorts and a meta-analysis of available published data, relevant to the 2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy performance, for SCD prevention has shown that pooled estimates are concordant with the observed SCD risk in patients designated as high or low risk.821–824 In children, risk stratification for SCD has traditionally been based on risk factors extrapolated from adults with HCM, but this approach does not identify the children most at risk of SCD. In 2019, the first validated paediatric-specific risk model for SCD was developed (HCM Risk-Kids; https://hcmriskkids.org), using a similar approach to HCM Risk-SCD,81,825 and has since been independently externally validated.535,797,826 A similar paediatric riskprediction model (PRIMaCY Childhood HCM Sudden Cardiac Death Risk Prediction tool) has also been developed, using similar clinical parameters and with similar reported accuracy to HCM Risk-Kids (https:// primacy.shinyapps.io/calculator/).535

In this update, the Task Force maintains the principle of risk estimation using the validated HCM Risk-SCD tool as the first step in sudden death prevention in patients aged 16 years or more, and recommends the use of a validated risk score (e.g. HCM Risk-Kids tool) for children and adolescents <16 years. This is in contrast to the 2020 AHA/ACC Guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy,793 in which the tool is considered an aid to a shared decision-making process for ICD placement in patients with clinical risk markers. This approach by the AHA/ACC, in part, reflected concerns that reliance on a risk tool does not account for individual patient perception and acceptance of pre-determined thresholds for medical intervention, as well as the omission of clinical risk markers such as LV systolic impairment from the HCM Risk-SCD model. The Task Force acknowledges the challenges associated with defining universal thresholds for acceptable risk, but feels that reliance on an unquantified estimate of risk does nothing to resolve this dilemma. Instead, the Task Force recommends more overt shared decisionmaking based on real-world data as well as individual preferences, beliefs, circumstances, and values. Gaps in evidence are acknowledged and should be shared with patients. Similarly, competing risks related to the disease (heart failure, stroke) and to age and comorbidity, as well as device-related complications, should be discussed.726,827,828 Critically, the Task Force calls for development of enhanced patient decision aids tailored specifically to receivers of care as well as more traditional decision-support tools for healthcare practitioners. Figure 16 summarizes the recommendations for primary prevention ICD implantation in HCM in each risk category. These take into account not only the absolute statistical risk, but also the age and general health of the patient, socioeconomic factors, and the psychological impact of therapy. The recommendations are meant to be sufficiently flexible to account for scenarios that are not encompassed by the HCM Risk-SCD or HCM Risk-Kids models. These models should not be used in elite athletes or in individuals with metabolic/infiltrative diseases (e.g. Anderson–Fabry disease) and syndromes (e.g. Noonan syndrome). The models do not use exercise-induced LV outflow tract gradients and have not been validated before and after myectomy. The HCM Risk-SCD model has been validated in one study of adult patients following ASA,829 and a recent study has suggested that severe LVH and residual LVOTO are associated with an increased risk of SCD following ASA, with a modest C-statistic of 0.68.830 Downloaded from academic.oup.com/eurheartj/article/44/37/3503/7246608 by guest on 07 October 2026