The importance of upright posture in exercise testing and training for patients with hypertrophic cardiomyopathy

Prior to the recent report by Klempfner et al.,1 formal and programmed exercise training has not been investigated as a treatment modality in patients with hypertrophic cardiomyopathy (HCM). The exclusion of this patient population is based on concern of risk of malignant arrhythmogenicity provoked by exercise-induced ischaemia; HCM is a major cause of sudden death in athletes and young individuals with fatal events not uncommonly triggered by physical exercise The ominously prognostic risk factor is abnormal (flat or even decreased) blood pressure reaction during upright exercise. The pilot study by Klempfner et al.1 has been prospectively evaluated for the feasibility and safety of a structured and monitored exercise training programme in symptomatic HCM patients. Innovatively, patient referral originated from the dedicated cardiomyopathy clinic to the cardiac rehabilitation centre of a specialist institution according to several strict criteria. The most important message from this study is that carefully supervised exercise training is well tolerated by patients with HCM, results in a significant improvement in symptoms and objectively measured functional capacity, and appears to be safe. In the past, HCM patients generally receive the recommendations to refrain from excessive physical activity. Such a recommendation is not only difficult to adhere to but also unrealistic. Klempfner et al.1 suggested that preventing interested patients from joining a supervised and suitable exercise programme may lead to an uncontrolled practice of physical activity, and thus, paradoxically, achieve an opposite effect. On the other hand, if patients adhere to the formal recommendations, they are compelled into leading a sedentary lifestyle that increases other risks such as obesity and coronary heart disease. Recently it has been reported that obesity in HCM patients was associated with left ventricular outflow tract (LVOT) gradient, and also risk of developing LVOT obstruction during stress.2 Exercise training may reduce obesity, and consequently decreases LVOT obstruction/gradient as well as provides a novel noninvasive method for nonpharmacological gradient reduction in patients with obstructive HCM. In the newest study,3 a group of adolescent subjects (with echocardiographically normal heart in relation to age at supine position) was observed also during exercise. Elevated LVOT velocities in this group monitored echocardiographically during upright (not supine) treadmill test may be a normal physiological response. The median peak LVOT velocity measured immediately after exercise was 2.5 m/s (range 1.3–5.9 m/s). Sixteen subjects (32%) developed peak LVOT velocities of ≥3 m/s (>36 mmHg). Twelve of the 16 (75%) with elevated velocities had a dynamic outflow tract Doppler pattern, of whom eight had evidence of intracavitary narrowing on two-dimensional echocardiography. This new observation needs to be studied more intensively. From the technical point of view, several previous studies4–9 have repeatedly demonstrated and emphasized the many advantages of measuring the LVOT gradient during treadmill exercise in the upright position over the bicycle exercise in the (semi) supine position in HCM patients. In the latest report, by Lafitte et al.,10 the authors clearly demonstrated the important role of dynamic load variation during/after exercise in patients with asymptomatic HCM. This pathophysiologically important phenomenon provided several valuable insights into the determinants of impairment of functional capacity in HCM. The investigators indicated and recommended the particular value of exercise echocardiography in the clinical assessment of HCM patients. The authors demonstrated clinically important clarification of the mechanism of dynamic obstruction partially associated with dramatic load variations as position dependent phenomenon. In view of these novel evidences,10 the question about the optimal exercise test protocol – upright versus supine position – seems to be particularly relevant. In the past, all studies investigating dynamic obstruction in HCM have focused on conventional treadmill exercise followed by echocardiographic recordings at recovery in a supine position. Lefitte et al.10 stated clearly that this approach cannot be considered to be a optimal evaluation of exercise dynamics, as dramatic preload variations are observed a few seconds after the end of effort, especially when using a bicycle test. They further stressed that, when the subject is upright at the end of lower limb muscle exercise, there is a large decrease in venous blood return to the heart, yielding: decreased left ventricular volume decreased wall stress continued sympathetic drive a hyperkinetic state like that observed during dobutamine-induced stress.10