Exercise stress test methodology and safety in hypertrophic cardiomyopathy

The authors presented a very important paper concerning sex differences in exercise capacity and prognosis in patients with hypertrophic cardiomyopathy.1 However, there is a potential bias caused by the retrospective character of the study with some limitations influencing the results. Left ventricular outflow tract gradient (LVOTG) was provoked by exercise using a semi-supine bicycle. Since 2014, European Society of Cardiology Guidelines for hypertrophic cardiomyopathy (HCM)2 recommend maximizing provocation by exercising in an upright position, which is based on a protocol proposed in 2009.3 The superiority of upright exercise over semi-supine exercise for LVOTG maximalization at peak exercise has been documented in a previous study.4 To sum up, the analysed group of patients experienced nonphysiological, submaximal exercise without achieving maximal LVOTG. It is likely that natural, physiologically upright exercise might have a better chance at achieving greater LVOTG at peak- and post-exercise. The smaller the dimension of the left ventricle (LV) cavity at rest (common in women)5 and the greater the reduction of LV preload in upright position, the greater the provoked LVOTG at peak- and post-exercise period is. The authors1 and Constantine et al.6 speculated that tailored activities and well-conducted training programs might provide a safe and effective measure to overcome functional impairments associated with sex in post-menopausal women. A recent paper postulated that a reduction in obesity and metabolic abnormalities by exercise training may be important and beneficial in modifying the clinical status of HCM.7 This hypothesis should be taken into consideration, keeping in mind the risk of exercise-induced ischemia in HCM. A recent study found that 50% of patients with HCM experienced myocardial ischemia at rest.8 Ischemic events were confirmed by positive results from high-sensitivity troponin tests.8 Importantly, half of the patients had painless angina (silent ischemia). In this particularly dangerous situation, patients may not receive any benefit from exercise training but may be harmed by it due to repeated, escalating ischemia. Importantly, ischemia is directly linked with myocardial dysfunction. The functional destruction by both types of ischemia (painful and painless) was documented previously.9 In conclusion, high-sensitivity troponin assays must be checked before and monitored after exercise to enable a safe training program for HCM patients. This safety protocol with troponin sampling might be particularly helpful in about 50% of HCM patients.