Table 2|. Troubleshooting table.

Step	Problem	Possible reason	Solution
Reagent setup	No hiPSCs produced during reprogramming	Low-quality reprogramming virus and reagents	Use fresh reprogramming virus and reagents; use a higher MOI or more PBMCs during reprogramming; use a hypoxia incubator during reprogramming
14	Spontaneously differentiating hiPSCs	Low-quality hiPSC lines with possible genetic irregularities	Scrape and repick hiPSC colonies with ideal morphologies; check passage number and expiration date of E8 medium
18	No hiPSC-CMs produced during differentiation	Line-to-line variability in hiPSC differentiation capacity	Try different concentrations of Wnt agonist (6–24 μM) CHIR99021; alter the starting confluency for hiPSC differentiation
19	Excessive hiPSC-CM death during glucose starvation selection process	hiPSC-CMs are somewhat immature and may not have completely shifted metabolically to utilizing lactate	End glucose starvation early for hiPSC-CMs; subject the cells to glucose starvation for a maximum of 2 d only if the cells cannot tolerate this environment
33	hiPSC-CMs do not survive well when replated into high-throughput screening plates	hiPSC-CM survival is dependent on cell confluency and extracellular matrix deposition	Use younger hiPSC-CMs for replating; increase Matrigel concentration; replate hiPSC-CMs at higher confluency; do not disturb hiPSC-CMs for 48 h after replating
36	Substantial hiPSC-CM death when thawing frozen hiPSC-CMs	Substantial cell loss is a known problem when thawing hiPSC-CMs	Use >10% FBS when thawing hiPSC-CMs; thaw at a higher confluency; use rho kinase inhibitor while thawing
41A(v)	High background during fluorescence imaging for drug-induced hiPSC-CM cytotoxicity assays	Plastic plates cause autofluorescence	Use low-autofluorescence multi-well imaging plates
42	Unable to compute the effective concentration metric for assessing hiPSC-CM contractility	Unable to gain access to a high-throughput contractility analysis platform such as the KIC	A simplified CSI (CSI-Lite) uses only the CoB concentration for assessing drug-induced alterations in hiPSC-CM contractility. Drug concentration causing CoB can be easily foun simply by looking at drug-treated wells
46	High well-to-well variability in hiPSC-CM contractility	Slightly different numbers of hiPSC-CMs plated per well or impure cell populations	Increase the number of technical replicates for contractility analysis; purify hiPSC-CMs for a longer time before replating; utilize well-specific baseline controls instead of vehicle controls