Fig. 2.

Echocardiographic data by age and sex in response to 1 week of isoproterenol (ISO). a Representative images from M-mode echocardiography. b Heart rate (HR) differed by condition and the interaction of age × condition. c SV differed by age (SV; juvenile < adult = aged). d Cardiac output (CO) differed by age (juvenile < aged= adult). e Ejection fraction (EF) differed by age (adult = juvenile < aged), sex, condition, and the interactions of age × condition, sex × condition, and age × sex × condition. f Fractional shortening (FS) differed by sex, condition, and the interaction of age × sex × condition. Data are presented as means ± SEM. *P < 0.05 as assessed by 3-way ANOVA and Fisher’s post hoc test to compare ISO and CON within age and sex, n = 4/group