It seems we are getting very poor doubling times from our recently differentiated cardiomyocytes. What should we be expecting?

Answer

As the pluripotent stem cells start to differentiate ( cardiac in this case), the expansion potential of PSC gets declined. The differentiated cells do not divide further, unless they are still in some progenitor state. Considering this dynamics in differentiating cell cultures, it is quite natural that doubling times tend to get poor and poor and eventually stop doubling. It is normal in differentiating cell cultures.