Association between myocardial strain and cardiopulmonary exercise testing in patients with hypertrophic cardiomyopathy

Introduction Hypertrophic cardiomyopathy (HCM) is a common hereditary condition with a wide phenotypic expression. Some individuals remain asymptomatic with a normal life expectancy, while others experience symptoms and severe cardiac events (1). Myocardial strain, assessed using cardiac magnetic resonance imaging (CMR), is a key quantitative measure of left ventricular (LV) deformation, providing valuable insights into ventricular function (2). Patients with HCM often present with both overt and subclinical LV dysfunction, along with reduced functional capacity. The relationship between myocardial strain and peak oxygen uptake (VO₂ peak) could be crucial in evaluating ventricular dysfunction and its impact on functional capacity, thereby aiding clinical management (3). Objective This study aimed to assess the association between myocardial strain and functional impairment, as measured by VO₂ peak from cardiopulmonary exercise testing (CPET) in patients with HCM. Methods A cohort of HCM patients underwent a comprehensive assessment, including transthoracic echocardiography, CMR, and CPET. CMR was performed using a 1.5-T scanner. Myocardial strain was analyzed using feature tracking, and late gadolinium enhancement (LGE) quantification was conducted with specialized cardiovascular imaging software. A linear regression model was applied to explore relationships between myocardial strain, clinical parameters, CPET data, echocardiographic findings, and CMR-derived LV metrics. Results The study included 32 HCM patients diagnosed between January 2017 and April 2023. Of these, 71% were male, with a mean age of 50 ± 15.3 years. The average LV ejection fraction was 70.8% ± 10.9%, mean myocardial strain was -12% ± 3.4%, and mean VO₂ peak was 25 ± 8 mL/kg/min. Myocardial strain was significantly associated with LGE extent (β = 9.8, p = 0.022) and indexed LV mass (β = 0.08, p = 0.001). However, no significant relationship was found between myocardial strain and VO₂ peak (β = -0.39, p = 0.358) or intraventricular pressure gradients (β = -0.001, p = 0.93). Conclusions In patients with HCM, CMR-derived myocardial strain is inversely correlated with LV mass index and the extent of myocardial fibrosis detected by LGE. These findings suggest that strain analysis is useful for assessing LV systolic function, particularly when traditional parameters remain within normal ranges. However, myocardial strain did not correlate with functional exercise capacity, as measured by CPET. Further research is needed to better understand the interaction between LV remodeling, myocardial fibrosis, and functional performance in HCM patients.