Three dimensional myocardial deformation parameters are associated with functional capacity in hypertrophic cardiomyopathy
Authors: Garcia Bras P , Aguiar Rosa S , Moura Branco L , Galrinho A , Valentim Goncalves A , Selas M , Silva F , Cardoso I , Grazina A , Viegas J , Ferreira R 
Published: February 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Introduction
Three-dimensional (3D) echocardiography is an emerging tool for assessment of left ventricular function, with a promising role in the evaluation of cardiomyopathies. Hypertrophic cardiomyopathy (HCM) is often associated with reduced exercise capacity. The aim of this study was to evaluate the importance of 3D myocardial deformation parameters as predictors of exercise capacity in HCM patients (P).

Methods
This prospective study enrolled P with HCM. Each P underwent a comprehensive transthoracic echocardiogram including 3D speckle-tracking to measure global longitudinal, radial and circumferential strain, twist, torsion and global area strain. Functional capacity was objectively assessed by treadmill cardiorespiratory exercise testing.

Results
83 patients with HCM, 50 (60%) male, mean left ventricular ejection fraction (LVEF) of 68 ± 7%, 27 (33%) with obstructive HCM (LV outflow tract [LVOT] gradient of 89 ± 60 mmHg). Impairment in LV myocardial deformation parameters was significantly correlated with lower peak VO2: global longitudinal 3D strain (r=-0.397, p &lt; 0.001), global radial 3D strain (r = 0.336, p = 0.003) and global circumferential 3D strain (r=-0.353, p = 0.002) (Figure 1).
Impaired LV twist was significantly correlated with inferior peak VO2 (r = 0.264, p = 0.033) (Fig.2) and peak circulatory power (r = 0.371, p = 0.003). Torsion impairment also significantly associated with lower peak VO2 (r = 0.285, p = 0.021), circulatory power (r = 0.380, p = 0.002), time to ventilatory anaerobic threshold (VAT) (r = 0.369, p = 0.003) and (VE/VCO2 slope)/peak VO2 ratio (r=-0.316, p = 0.012).
Furthermore, global area strain impairment showed significant relation with decreased peak VO2 (r=-0.368, p = 0.001), lower exercise duration (r=-0.384, p = 0.001), time to VAT (r=-0.404, p &lt; 0.001), circulatory power (r=-0.272, p = 0.032) and (VE/VCO2 slope)/peak VO2 ratio (r = 0.391, p = 0.002). LV twist (r=-0.135, p = 0.284), torsion (r=-0.120, p = 0.341) and global area strain (r = 0.152, p = 0.235) impairment did not correlate with VE/VCO2 slope. Exercise capacity was not associated with LV mass index (r = 0.209, p = 0.095), LV end-diastolic volume (r = 0.058, p = 0.639), maximum wall thickness (r = 0.041, p = 0.744), LVEF (r=-0.092, p = 0.458), 2D global longitudinal strain (r=-0.024, p = 0.848) or peak LVOT gradient (r=-0.006, p = 0.964). In a subanalysis examining only the nonobstructive (nHCM) P, we found that peak VO2 had a superior correlation with global longitudinal 3D strain (r=-0.420, p = 0.004), global radial 3D strain (r = 0.356, p = 0.016) and global circumferential 3D strain (r=-0.357, p = 0.016) as well as LV twist (r = 0.300, p = 0.046) and torsion (r = 0.336, p = 0.024).

Conclusion
Although P with HCM often have supranormal LVEF, 3D speckle-tracking echocardiographic imaging has the potential to demonstrate subclinical impairment of LV function. Impaired LV 3D strain, twist, torsion and global area strain were associated with reduced exercise capacity, particularly in nHCM P. Abstract Figure. Peak VO2 and 3D strain parameters Abstract Figure. LV twist, torsion and global area strain