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.................................................................................................................................................................... induced symptoms should be advised to engage in low-intensity recreational sports only.

5.5.1.4 Resting and ambulatory ECG The resting 12-lead ECG has limited value in risk stratification. Ambulatory ECG monitoring, preferably for 48 h, is important for detecting ventricular and supraventricular arrhythmias. The monitoring period should include an exercise session. Asymptomatic nonsustained ventricular tachycardia (NSVT) confers considerable risk of SCD in younger individuals (<_35 years).355 Paroxysmal supraventricular arrhythmias may pose significant implications for functional capacity and, in the case of AF, for stroke prevention.366

5.5.1.5 Echocardiography In relation to risk stratification for SCD the clinician should assess the following echocardiographic indices: (i) LV wall thickness; (ii) LV outflow tract (LVOT) gradient; and (iii) left atrial diameter.355 All individuals should have the LVOT gradient assessed at rest, during the Valsalva manoeuvre, on standing suddenly, and after light exercise on the spot, such as repeated squats. By convention, LVOT obstruction is defined as a peak pressure gradient >_30 mmHg at rest or during physiological provocation. A gradient >_50 mmHg is considered to be haemodynamically important. Exercise stress echocardiography should be considered in individuals with exertional symptoms who have resting systolic anterior motion of the mitral valve leaflets but who do not reveal LVOT obstruction or show only mild to moderate LVOT obstruction with the aforementioned manoeuvres.

5.5.1.6 Cardiac magnetic resonance imaging CMR imaging is increasingly recognized as a necessary tool for confirming diagnosis and to assess risk stratification in individuals with HCM. Late gadolinium enhancement (LGE), indicative of myocardial fibrosis, may be present in up to 75% of patients with HCM and, by itself, is a poor discriminator of outcomes. However, the presence of extensive (>_15% of LV myocardium) LGE may identify individuals at increased risk of ventricular tachyarrhythmias and SCD.367370

5.5.1.7 Exercise testing Exercise testing (or CPET) should be part of the routine evaluation to assess functional capacity in an individual with HCM who intends to exercise. In addition, an abnormal BP response to exercise (defined as <20 mmHg increase in SBP from baseline, or exerciseinduced hypotension)371,372 and the presence of exercise-induced symptoms or arrhythmias are markers of high risk and should result in more conservative exercise recommendations.

5.5.1.8 Genetic testing Currently genetic testing is reserved for familial cascade screening. It does not inform decisions relating to the risk of SCD/SCA and should not be performed for exercise risk stratification.

5.5.1.9 ESC risk score in HCM The ESC risk score uses seven variables (age, syncope, family history of SCD from HCM, maximal LV wall thickness, left atrial diameter, LV outflow obstruction, NSVT) to assess the risk of SCD of patients with HCM.355,373 This information can be inserted into an online calculator (https://doc2do.com/hcm/ webHCM.html) to estimate individualized 5-year risk to provide guidance on whether a prophylactic ICD is indicated. For the purposes of these Guidelines the risk of SCD is defined as low if <4%, moderate if between >_4% and <6%, and high if >_6% in 5 years.

5.5.1.10 Exercise recommendation On completion of the baseline evaluation, the physician should consider: (i) the presence of symptoms; (ii) ESC risk score; (iii) presence of resting or inducible LVOT obstruction during exercise; (iv) the haemodynamic (BP) response to exercise; and (v) the presence of resting or exercise-induced arrhythmias before recommending the appropriate form and intensity of exercise. Although these Guidelines advocate for a more liberal approach to sports participation, it is indisputable that even the absence of all major risk factors does not convey immunity to SCD.374 In addition, the ESC risk score relies on evidence derived from predominantly non-athletic cohorts.373 Whereas there are no data to suggest that this approach to risk estimation is less valid in athletic individuals, one has to consider that it may not accurately reflect the risk of SCD in individuals exposed to the haemodynamic and metabolic stresses of high-intensity sports. Therefore, when advising an individual with HCM regarding participation in high-intensity exercise programmes and competitive sports, this consideration should be an integral part of the discussion during the shared decision-making process.

5.5.1.11 Special considerations The age of an individual may have an impact on risk. The mean age of death in the largest series of SCD from the US was 18 years, with 65% of deaths occurring in athletes <_17 years.354 Although young age should not exclude an individual from high-intensity exercise in the absence of additional risk factors, it should be considered in the discussion with the individual and the parents or guardians. In addition, specific sports may pose a higher risk for SCD, such as highly dynamic, startstop sports like basketball and football.17,58 Individuals who have a positive genotype but who do not reveal any phenotypic structural or arrhythmia features of HCM may engage in all sports. Such individuals should be assessed annually for phenotypic features and risk stratification purposes.

5.5.1.12 Follow-up Annual follow-up is recommended for most individuals with HCM who exercise on a regular basis. More frequent (6-monthly) followup should be considered in adolescent individuals and young adults whose phenotype, and therefore risk of SCD, may still be evolving and who are more vulnerable to exercise-related SCD.58,239Followup evaluation should focus on assessment of disease progression and risk stratification. New symptoms should prompt interruption of exercise and re-evaluation. Downloaded from academic.oup.com/eurheartj/article/42/1/17/5898937 by guest on 07 October 2026