Figure 3.

HHR cardiomyocyte hypercontractility characterizes progression to failure with preserved systolic function (20–30 weeks). A, Bright field normal heart rat (NHR) and hypertrophic heart rat (HHR) cardiomyocyte micrographs. B, Mean computed cardiomyocyte volume from 2‐dimensional isolated myocyte measurements (n=mean 50 cells for N=16–22 hearts). C and D, Fura‐2 loaded isolated myocyte exemplar records: shortening and Ca²⁺ transients. E through G, Cardiomyocyte mean maximum % shortening (normalized for myocyte length), and mean Ca²⁺ diastolic and twitch amplitude levels (n=16–17 cells for N=10 hearts/group). H through J, Regression plots: myocyte size (μm) vs % shortening, diastolic Ca²⁺ and peak systolic Ca²⁺ levels (n=16–17 cells from N=10 hearts/group). K and L, Exemplar “Phase‐loop” plots of cardiomyocyte length vs Ca²⁺ during activation cycle show HHR right‐shift, with significantly higher Ca²⁺ at 50% myocyte relaxation, indicating reduced sensitivity to Ca²⁺ levels (n=16–17 cells from N=10 hearts/group). Graphs show mean ± SEM, For B, E through G, and L, *P<0.05 (Student t test). For H through J, P value, Pearson's correlation.