cTnI-ND,Tnni3 ^−/− hearts have longer LV ejection time at high preload. (A) Determination of LV ejection time of ex vivo working heart from the dP/dt of aortic pressure (AP) development curves. The first and highest peak of +dP/dt of AP development indicates the full opening of the aortic valve, which marks the beginning of the ejection phase. The end point of AP descending when the dP/dt of AP development = 0 indicates the closing of the aortic valve and the end of LV ejection. The total duration of LV ejection is divided at the peak of LVP into the rapid and reduced ejection phases. (B) LV total ejection time increased in both cTnI-ND,Tnni3^−/− and WT hearts when preload was increased, which was longer in cTnI-ND,Tnni3^−/− hearts especially at preloads above 12.5 mmHg due to continued positive response vs. the plateau in WT hearts. The duration of rapid ejection phase was similar in the two groups while cTnI-ND,Tnni3^−/− hearts exhibited a trend of longer time at low preloads. The reduced ejection phase was longer in cTnI-ND,Tnni3^−/− hearts than that in WT hearts at the higher preloads of 10–20 mmHg. n = 6 mice in WT and 9 mice in cTnI-ND,Tnni3^−/− groups. Values are mean ± SEM. ***P < 0.001 vs. WT in two-way ANOVA with post-hoc method of Tukey’s test.