Analyses of individual sarcomeric movements in the left ventricle with varying levels of contractility. (A) Top left: Confocal image of an α-actinin-AcGFP–expressing LV myocyte in a heart with depressed cardiac function during deep anesthesia (∼5% isoflurane). ΔLVP, 7.2 ± 0.1 mm Hg; HR, 159 ± 45.4 bpm (see Fig. S18 A). In the yellow-outlined rectangle, nine sequentially connected sarcomeres were analyzed for M1. Scale bar, 10 µm. See Video 8. Bottom left: Triangular heat map showing correlation between average and individual SLs (top row) and between an individual sarcomere and other sarcomeres in M1 (second row and below). Sarcomere number (i.e., from nos. 1 to 9 [or average]) is indicated on top and left of each row. Top right: Confocal image of an α-actinin-AcGFP–expressing myocyte in the left ventricle just before cardiac arrest under deep anesthesia with ∼5% isoflurane. ΔLVP, 4.7 ± 0.2 mm Hg; HR, 80 ± 14.2 bpm (see Fig. S18 B). In the yellow-outlined rectangle, seven sequentially connected sarcomeres were analyzed for M1. Scale bar, 10 µm. See Video 9. Bottom right: Triangular heat map showing the correlation between average and individual SLs (top row) and between an individual sarcomere and other sarcomeres in M1 (second row and below). Sarcomere number (i.e., from nos. 1 to 7 [or average]) is indicated on top and left of each row. In bottom left and right, CI is shown based on a color scale (i.e., from 1 [dark blue] to −1 [dark red]). (B) Bar graph showing the fractions of CI between average and individual SLs at various levels of ΔLVP. Data at 135.7, 96.4, 60.5, 40.6, 7.2, and 4.7 mm Hg are shown. CI was categorized into the following three groups: blue (CI > 0.2 [positive correlation]), white (0.2 > CI > 0 [no correlation]), and red (CI < 0 [negative correlation]). (C) Relationship between ΔLVP and the fraction of contributing sarcomeres in myofibrils from mice with varying contractile conditions. Contributing sarcomeres are defined as those with CI >0.2 in the average data of three to eight cardiac cycles. Each plot indicates a myofibril (i.e., sequentially connected sarcomeres). A significant relationship was observed (R = 0.90; P < 0.001). (D) Plots of CI between average and individual SLs at various levels of ΔLVP. A significant difference (*, P < 0.05) was observed between ΔLVP 96.4 mm Hg and 135.7 mm Hg and between ΔLVP 96.4 mm Hg and 4.7 mm Hg, but not between ΔLVP 96.4 mm Hg and 60.5, 40.6, or 7.2 mm Hg (n.s.). Horizontal bars, average; vertical bars, SD. (E) Relationship between ΔLVP and the average values of CI (Avg. CI) in D. A significant linear relationship (R = 0.93; P < 0.01) was observed. In B–E, two myofibrils were analyzed for ΔLVP 96.4, 60.5, 40.6, and 7.2 mm Hg (Figs. 3, S6, and S18), and three myofibrils were analyzed for 135.7 and 4.7 mm Hg (Figs. S15 and S18).