the total live cell count obtained on day 12, good CM yields fall

around 1.9  10⁶/mL [3, 9]. Percentage of cells beating falls

around 70% [12].

18. Attempt to break MC clumps and dissociate cells by pipetting

after 5 min incubation is complete. If MC clumps remain, place

back into 37 ^C for longer incubation. It can take up to 2 h for

cardiomyocytes to properly detach and dissociate from MC

clumps depending on the original hiPSC line used. If too

much pipetting is required to remove the cells or if clumps

remain stubborn, incubate it for more time at 37 ^C on a

shaker at 75 rpm.

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