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7.1.5.1 Left ventricular apical aneurysms

Left ventricular apical aneurysms are defined as a discrete thin-walled dyskinetic or akinetic segment of the most distal portion of the left ventricle and are often associated with a mid-cavity gradient. Their prevalence in unselected patients is uncertain but they were reported in 3% of individuals in the prospective Hypertrophic Cardiomyopathy Registry (HCMR).124 The first descriptions of LV apical aneurysms in HCM suggested an association with sustained monomorphic ventricular tachycardia (SMVT)730—a relatively rare occurrence in HCM—and a number of studies have suggested that they are a useful marker of SCD risk.580,728,736,737,791,792 Based on these data, LV aneurysms were included in the recent 2020 American Heart Association/American College of Cardiology (AHA/ACC) HCM guideline as a major independent SCD risk factor and were considered a reasonable sole indication for an ICD.793 In a review for this guideline, the data from two published studies and a meta-analysis were evaluated (see Supplementary data online, Table S2). All these studies were retrospective and the absolute number of events is too small to assess the independent predictive value of apical aneurysms. In two small series that described a selected subgroup of HCM patients with mid-ventricular obstruction, there was no increase in incidence of SCD events. In the only series that provides a detailed analysis of SCD events, the majority were appropriate ICD interventions for monomorphic VT, suggesting significant inclusion bias.737 Finally, a large proportion of individuals with events had other important risk markers including prior sustained ventricular arrhythmia. Based on the current data, the Task Force recommends that individualized ICD decisions should be based using well-established risk factors and not solely on the presence of an LV apical aneurysm.

7.1.5.2 Left ventricular systolic dysfunction

A small number of retrospective studies and two larger registries have examined the relation between prognosis in patients with HCM and LV systolic dysfunction (most frequently defined by a LVEF <50%) (see Supplementary data online, Table S3). All studies consistently show an increased rate of SCD events in patients with left ventricular systolic dysfunction (LVSD) ranging from 7 to 20% compared with that of patients with normal LV systolic function. However, the independent and additional value of LVSD compared with current risk stratification tools has not been investigated. There is only one multivariable model that investigates the independent relation of LVSD to the risk of SCD events but the covariables examined were limited (age, sex, and follow-up time).315 As with other recently proposed risk markers in HCM, the Task Force maintains its recommendation to first estimate SCD risk using the HCM-SCD Risk and HCM Risk-Kids tools, and then to use the presence of an LVEF <50% in shared decision-making about prophylactic ICD implantation, with full disclosure of the lack of robust data on its impact on prognosis.

7.1.5.3 Late gadolinium enhancement on cardiac magnetic

resonance imaging In the 2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy, the extent of LGE on CMR was considered helpful in predicting cardiovascular mortality, but data at that time were felt insufficient to support the use of LGE in prediction of SCD risk. Since then, more studies have been published (see Supplementary data online, Table S1). In aggregate, the data show that LGE is common and, that when extensive (expressed as a percentage of LV mass), is associated with an increase in SCD risk and other events, particularly in the presence of other markers of disease severity including LV systolic impairment. A meta-analysis of nearly 3000 patients from several studies suggests that the presence of LGE is associated with a 2.32-fold increased risk of SCD/aborted SCD/appropriate ICD discharge, and a 2.1-fold increase in all-cause mortality.794 It has been suggested that the addition of LGE to the current AHA/ACC sudden death algorithm or the HCM-SCD risk model improves stratification of patients who are otherwise considered low or intermediate risk.793

As in 2014, a number of uncertainties persist. These include the inevitable confounders in the retrospective studies that bias towards high-risk patients or patients referred specifically for septal myectomy. There also remains some debate about the methods used to quantify LGE with the 2-standard deviation technique; the only one that is validated against necropsy.605 Retrospective CMR series also report relatively high event rates suggesting that they are not representative of the broad spectrum of disease. In HCMR, a prospective CMR study of 2755 patients, LGE was present in 50% of patients based on visual criteria and in 60% based on >6 SCD signal criteria, but only 2% of patients had LGE >15% of LV mass.124 In the most recent report from the registry, there have been 24 deaths from any cause after a mean follow-up of 33.5 ± 12.4 months (median: 36 months and range 1–64 months); the relation with LGE is not reported.795 There are very limited data on the role of CMR over and above validated risk algorithms in SCD risk prediction in children with HCM.796,797 On balance, the Task Force maintains the recommendation to first estimate SCD risk using the HCM-SCD Risk calculators. For patients who are in the low to intermediate risk category, the presence of extensive LGE (≥15%) may be used in shared decision-making with patients about prophylactic ICD implantation, acknowledging the lack of robust data on the impact of scar quantification on the personalized risk estimates generated by the HCM-SCD Risk calculators.

7.1.5.4 Abnormal exercise blood pressure response

Approximately one-third of adult patients with HCM have an abnormal systolic blood pressure response to exercise characterized by progressive hypotension or a failure to augment the systolic blood pressure that is caused by an inappropriate drop in systemic vascular resistance and a low cardiac output reserve.798,799 Various definitions for abnormal blood pressure response in patients with HCM have been reported;590,765,768,782 for the purposes of this guideline, an abnormal blood pressure response is defined as a failure to increase systolic pressure by at least 20 mmHg from rest to peak exercise or a fall of >20 mmHg from peak pressure.590,765,768,782,800 Abnormal exercise blood pressure response may be associated with a higher risk of SCD in adult patients aged ≤40 years, but it has a low positive predictive accuracy and its prognostic significance in patients >40 years of age is unknown, and recent data have suggested that, although it may be associated with increased overall mortality largely related to heart failure, it is not consistently associated with an increased risk of ventricular arrhythmia or SCD.800,801 There is no evidence to suggest that abnormal blood pressure response to exercise is associated with a higher risk of SCD in children with HCM.802 The Task Force, therefore, does not recommend the use of abnormal blood pressure response to exercise as an indication

ESC Guidelines                                                                                                                                                                                          3559

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