Reduced Myocardial Reserve in Young X-Linked Muscular Dystrophy Mice Diagnosed by Two-Dimensional Strain Analysis Combined with Stress Echocardiography

Abstract

Early, sensitive, and reproducible evaluation of left ventricular function is imperative for the diagnosis of cardiac dysfunction in patients with Duchene muscular dystrophy. The aim of this study was to test the hypothesis that combining two-dimensional strain analysis with catecholamine stress could be a sensitive method for detecting early cardiac dysfunction. Mdx (C57BL/10ScSn-Dmdmdx/J, a mouse model of DMD) and control (C57BL/10ScSn) mice were studied with conventional M-mode and high-frequency ultrasound-based two-dimensional speckle-tracking echocardiography using long- and short-axis images of the left ventricle at baseline and after intraperitoneal isoprenaline (ISO) administration (2μg/g body weight). Conventional M-mode analysis showed no differences in left ventricular fractional shortening, wall thickness, or internal diameter at diastole between mdx and control mice before the age of 6months. ISO increased left ventricular ejection fraction and fractional shortening to the same extent in mdx and control mice at young ages (3, 4, and 5months). No differences in basal peak systolic strain (PSS) but increased SDs of times to PSS between young mdx and control mice were found. After ISO, PSS and percentile changes of PSS were significantly diminished in mdx mice compared with control mice at young ages. ISO increased the normalized maximum difference of times to PSS in young mdx mice but not in young control mice, suggesting that ISO reduces cardiac contractile synchrony in young mdx mice. This study suggests that catecholamine stress coupled with two-dimensional strain analysis is a feasible and sensitive approach for detecting early onset of cardiac dysfunction, which is instrumental for early diagnosis of cardiac dysfunction and early treatment.