Contractile force measurement under electrical pacing.

<p>(A) Relationship between pacing rate and beating rate. Each value of beating rates was determined as the number of beatings in one minute during pacing. The dotted line indicates the equality between pacing rate and beating rate. (B) Relationship between beating rate and contractile force (i.e., force-frequency relationship). Each value of contractile forces was determined as the mean of those values in one minute during pacing. (C) Relationship between beating rate and |dP/dt min|. Each value of |dP/dt min| was determined as the mean of those values in one minute during pacing. In all figures, the results are presented as mean ± SD for 5 cardiac cell sheet-tissues. Among the 5 cardiac cell sheet-tissues, 2 samples were prepared from a same differentiation batch. The other 3 samples were prepared from different 3 differentiation batches respectively. For (B) and (C), each value of contractile forces was statistically compared to the value at 67 bpm (closed circles) using Student’s t-test (* p < 0.05, ** p < 0.01).