ABC | Volume 114, Nº5, May 2020

Arq Bras Cardiol. 2020; 114(5):943-987 Guidelines Brazilian Cardiovascular Rehabilitation Guideline – 2020 6.6.1.2. When Is Physical Exercise Indicated? The intensity of exercise which patients with HCM can be cleared to do still represents a major challenge. If, on the one hand, intense physical exercise can be harmful, with an increased risk of potentially fatal arrhythmias, on the other hand, excessive restrictions on physical activity lead to deconditioning and can have negative effects on health and quality of life; they may even increase cardiovascular risk, given the well-established association between physical fitness and mortality. 280,281 In its official position statement on management of HCM, the American Heart Association discourages patients with the disease from engaging in competitive sports of moderate to vigorous intensity (see Table 8). This limitation is meant to minimize sudden changes in BP and increases in cardiac output in order to protect patients from the negative effects of exercise on a pathologically hypertrophic heart. 283 Exercise-triggered arrhythmias (in the short term) and adverse myocardial remodeling (in the long term) are the most fearsome side effects of exercise in HCM. The fear of SCD during sport extends to non-competitive athletic activities, although there is a clear lack of evidence about the safety of exercise in this patient profile. However, it should be emphasized that this risk of exercise is theoretical, and that recommendations to limit physical activity have been advocated with caution, based solely on the opinion of experts, and are not supported by more robust evidence. 284 Thus, patients with HCM receive little guidance regarding the best dose or amount of physical activity to maintain general health and well-being; instead, greater focus is placed on restrictions on physical activities. As a result, more than 50% of patients with HCM do not achieve the minimum recommended physical activity target due to the belief that they are unable to exercise and/or that physical activity can worsen their disease. Therefore, a balanced approach seems to be most appropriate, and extremes should be avoided (neither vigorous competitive exercise nor physical inactivity), as both could increase cardiovascular risk. New evidence suggests a positive effect of moderate physical exercise in selected patients with HCM, with individualized risk assessment and exercise prescription. It is noteworthy that the evidence suggests benefits of MICT, while other modalities need further studies. However, the presence of any of the following could be considered major contraindications to the practice of exercise: history of aborted SCD in the absence of an ICD; history of syncope on exertion; exercise-induced ventricular tachycardia; increased exercise pressure gradient (greater than 50 mmHg); and abnormal BP response to exertion. 6.6.1.3. Pre-Exercise Evaluation Clearance to begin exercising must be based on the pre‑exercise evaluation, including a thorough history, physical examination, and 12-lead ECG. A large proportionof individualswithHCMare asymptomatic or oligosymptomatic; clinical suspicion is raised only by changes on resting ECG, which is abnormal in up to 95% of patients with the disease. 285 Electrocardiographic changes may precede structurally detectable disease for some years, which makes ECG extremely important in this scenario. 269 Only a minority of patients with HCM present with a normal ECG – usually those without any other phenotypic manifestations (positive genotype/negative phenotype). Echocardiography remains the most widely used modality for diagnosis of HCM. Magnetic resonance imaging (MRI) is usually reserved for cases in which echocardiography is in conclusive, or to assess more localized hypertrophy (e.g., apical forms). In young athletes, distinguishing physiological hypertrophy (“athlete’s heart”) from the pathological hypertrophy of HCM is a challenge. This is because, most athletes with HCM exhibit an asymmetric pattern of left ventricular hypertrophy, as do sedentary individuals with the condition. In contrast, those with physiological left ventricular hypertrophy show a more homogeneous, symmetrical distribution of wall thickness, with only minor differences between contiguous segments and a symmetrical pattern of left ventricular hypertrophy. 286 Exercise testing is always recommended in these patients prior to the start of CVR, whether to assess functional capacity or to detect abnormal BP responses and signs of increased dynamic obstruction of the outflow tract with exertion. For better detection of outlet tract obstruction during exercise, a combination of imaging (echocardiography) with stress testing is the gold standard and should be encouraged whenever possible. Patients with no obstruction at rest can present significant gradients on exertion, and thus be reclassified in relation to prognosis. 287 When available, CPET is advised instead of TMET, as it allows direct measurement of VO 2 peak, a parameter with documented prognostic value. 280,281 In addition, determining ventilatory thresholds contributes to a more individualized exercise prescription. 6.6.1.4. Special Considerations for the Prescription and Follow-Up of Physical Exercise Programs Some particularities of exercise in patients with HCM should be noted: • So-called “explosive” activities (e.g., basketball, football, tennis), with the potential for rapid acceleration and deceleration, should be avoided. • Activities with steady, constant energy consumption (e.g., light jogging or swimming) are preferred. • Exercise in adverse environmental conditions, including extreme heat or cold, should be avoided, as there is an increased risk of exacerbating exercise-induced physiological changes. • Training programs that aimcompetitivity, or achievement of higher levels of fitness and excellence, should be avoided, as they usuallymotivate patients to strive beyond safe limits. • Intense static (isometric) exercises, such as weight lifting, should be avoided, as there is an increased risk of left ventricular outflow tract obstruction due to the intense Valsalva maneuver involved. 966