Response of isolated, contracting dystrophic isolated hearts to ex vivo stretch.
A, B) Compressed representative pressure tracings from WT(A) and mdx (B) hearts during ex vivo stretch protocol. Inset: uncompressed pressure tracings from mdx and WT hearts prior to stretch, vertical scale bar = 50 mmHg, horizontal scale bar = 1/7 sec. C) Volume required to reach 8 mmHg EDP within the LV (Vinit). D) Altered whole-organ compliance of mdx and DKO hearts compared to WT as shown by plotting LVEDP against volume added above Vinit during ex vivo stretch. Mdx carrier females show normal whole-organ compliance. E) Differences in compliance of mdx and WT hearts are further exaggerated when plotting %Vinit versus LVEDP. F) Estimation of the true LV volume-EDP relationship based on data from 1C and 1D. Balloon only controls are shown to prove that recorded changes in pressure were not due to overfilled balloon. G) Whole-organ compliance of isolated WT and mdx carrier female hearts shown as the LV volume versus LVEDP. H) Whole-organ compliance of isolated mdx and DKO hearts shown as LV volume versus LVEDP. n = 5–14. For C, * - P<0.05 by t-test. For D, * - p<0.05 for C57BL/10SnJ vs. DKO, ∧ - P<0.05 for C57BL/10SnJ vs. mdx, † - p<0.05 for mdx versus DKO by two-way ANOVA with main effects for strain, volume, and an interaction of the two. Values expressed as mean ± SEM.