Flag-RadΔCT hearts show elevated function under basal conditions. Heart function was evaluated by echocardiography. (A) Representative M-mode recordings from Flag-Rad (left) and Flag-RadΔCT mice (right). The upper panel shows recording prior to ISO injection and lower panel shows same mice 1–3-min after ISO injection. (B) Ejection fraction (%) for male (left) and female mice (right) was significantly different between genotypes in the basal condition and significantly different in Flag-RAD after ISO. Sex as a main effect was not statistically significant (three-way repeated measures ANOVA, F = 1.050, P = 0.3113). Repeated measures two-way ANOVA’s were performed considering repeated measures basal versus acute ISO treatment and genotype (male: treatment F = 78.13, P < 0.0001; genotype F = 0.3790, P = 0.5435; interaction F = 62.75 P < 0.0001) (female: treatment F = 134.1, P < 0.0001; genotype F = 0.2705, P = 0.6101; interaction F = 95.04, P < 0.0001). Scale bar = 200 ms.