Identification of global and regional myocardial dysfunction in hypertrophic cardiomyopathy by three-dimensional speckle tracking echocardiography and relationship with left ventricular hypertrophy, and fibrosis by late gadolinium enhancement cardiovascular magnetic resonance

Resumen

Background. Hypertrophic cardiomyopathy (HCM) is a genetic disease of the cardiac sarcomere characterized by hypertrophy of ventricular walls with a wide spectrum of morphologic and hemodynamic abnormalities, and clinical manifestations. Both hypertrophy and fibrosis can be considered part of the histological and structural spectrum of HCM, and have been proposed to have notable implications in global and regional cardiac function. The presence of myocardial fibrosis, accurately measured by late gadolinium enhancement (LGE) sequences on cardiovascular magnetic resonance (CMR), has been consistently related to the magnitude of hypertrophy in patients with HCM. Whether myocardial fibrosis has an independent effect on left ventricular (LV) function beyond its relationship in location with LV hypertrophy has not yet been clearly elucidated. In this background, advanced imaging techniques, such as speckle tracking echocardiography (STE), might carry potential to detect global and regional cardiac function impairment due either to hypertrophy or to fibrosis, and so improve the diagnostic and prognostic evaluation of HCM. The utility of 3-dimensional STE is being increasingly explored in cardiovascular imaging centers; several research studies and analysis software improvements have led 3D-STE to become a promising tool for accurate evaluation of global and regional cardiac function, as well as cardiac chamber volumes. Little data have been reported on LV regional mechanics related to hypertrophic and fibrotic areas in patients with HCM, and the data are mostly based on tissue Doppler imaging and 2-dimensional analysis algorithms. Application of 3D-STE in HCM, and characterization of LV regional mechanics in relationship with myocardial hypertrophy and fibrosis, may provide new insights into the diagnosis and prognostication of this condition. Hypotheses. Heterogeneous myocardial hypertrophy and fibrosis, both characteristic of HCM, are responsible for global and regional abnormalities of LV myocardial mechanics, whose quantitative assessment is largely challenging by conventional cardiovascular imaging techniques. Objectives. To characterize LV global and regional myocardial mechanics by study of myocardial deformation over specific areas with and without significant hypertrophy (detected by standard echocardiography) and fibrosis (detected by LGE-CMR) in patients with HCM, by means of 3D-STE; to study the relationship between myocardial deformation parameters derived from 3D-STE and myocardial hypertrophy (quantified by standard echocardiography), as well as myocardial fibrosis (quantified by LGE-CMR). Methods. Fifty-nine patients with HCM underwent standard echocardiography, 3D-STE and LGE imaging on CMR, all 3 tests less than 24 h apart. Longitudinal, circumferential and area strains (LSt, CSt, and ASt) were investigated according to the extent of LGE (no LGE, LGE<10%, and LGE¿10%), segmental thickness (¿15mm vs. <15mm segments) and segmental presence of LGE (LGE vs. non-LGE segments). Results: Attenuated global LSt showed association with extent of hypertrophy (indexed LV mass, r=0.32, p=0.01; maximum LV wall thickness, r=0.38, p=0.003; number of significantly hypertrophied segments [¿15mm], r=0.44, p<0.001), while enhanced global CSt was correlated to LV global functional parameters (indexed LV end-systolic volume, r=0.47, p<0.001; LV ejection fraction, r=-0.75, p<0.001). None of the global myocardial mechanics parameters showed differences according to the extent of LGE, which in contrast showed to be related to the extent of hypertrophy. All 3 deformation parameters were attenuated both in segments with significant hypertrophy (¿15mm) and in LGE segments; adjusted analysis demonstrated that segmental presence of LGE added significant attenuation to deformation parameters only in those areas featuring significant hypertrophy. Conclusions: Left ventricular deformation myocardial mechanics are altered in HCM, with both hypertrophy and fibrosis contributing to regional impairment of longitudinal myocardial shortening. Disease burden in HCM, represented by the extent of hypertrophy, is the main factor associated with the alteration of myocardial mechanics, superior to even the presence and extent of fibrosis, which predominantly occurs in the most hypertrophied areas. Left ventricular myocardial shortening in the circumferential direction, measured by 3D-STE, seems to play a significant role in the maintenance of LV systolic performance in HCM, and might represent a valuable parameter in the follow-up of these patients.