A, representative examples of pressure recorded from perfused hearts isolated from mice with different FI scores. B, pressure recordings illustrated in A shown at an expanded time scale to illustrate differences in +dP/dt and –dP/dt. C–E, scatterplots plus box and whisker plots demonstrate that LVDP, +dP/dt and –dP/dt decreased with age. F–H, regression lines show that LVDP, +dP/dt and –dP/dt were graded by FI score and declined as frailty increased (n = 11 adult and 30 aged mice). Differences between age groups were assessed with either a t test or a Mann–Whitney Rank Sum test; correlations were performed with linear regression analysis. Filled symbols indicate adult mice and open symbols indicate aged mice.