HCN4 and hydrops fetalis: HF perfused microtissues showed the most significant transcriptional alteration from Day 1 to Day 5 (Figure 6), with increased expression of a wide group of genes, including pacemaker channels (HCN2 and HCN4; Figure S4), sodium channels (SCN1B; Figure S6), potassium channels (KCND3 and KCNH2; Figure S6), calcium cycling apparatus (CACNA1C, SCL8A1, ATP2A2, RYR2, and CASQ2; Figure S7), sarcomere structure (MYH6, MYH7, MYBPC3, TNNC1, TNNT2, TNNI3, and ACTC1; Figure S3), cell membrane and cytoskeleton (CAV3, JPH2, and ACTB; Figure S8) and metabolism regulators (PPARGC1A; Figure S9).