Background
Early, sensitive and reproducible evaluation of left ventricular (LV) function is imperative for diagnosis of cardiac dysfunction in Duchene muscular dystrophy (DMD) patients. We hypothesized that combining 2D-strain analysis with catecholamine stress could be a sensitive method for detecting early cardiac dysfunction.
Methods
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 2D speckle tracking echocardiography (STE)using long- and short-axis images of LV at baseline and after isoprenaline (2μg/g BW, i.p.).
Results
Conventional M-mode analysis showed no differences in LV fractional shortening, wall thickness or internal diameter at diastole between mdx and control mice before the age of 6 months. Isoprenaline increased LV ejection fraction and fractional shortening to the same extent in mdx and control mice at young ages (3, 4 and 5 months). No differences in basal peak systolic strain (PSS) but increased standard deviations of times to PSS between young mdx and control mice were found. After isoprenaline, PSS and percentile changes of PSS were significantly diminished in mdx mice compared to control mice at young ages. Isoprenaline increased normalized maximum difference of times to PSS in young mdx mice but not in young control mice, suggesting isoprenaline reduces cardiac contractile synchrony in young mdx mice.
Conclusions
Our study suggests that catecholamine stress coupled with 2D 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.