HCN4 and hydrops fetalis: However, HF perfused microtissues at Day 5 presented with the most notable transcriptional shift when compared with time‐matched static and LF conditions (Figure 6), with higher expression of connexin 43 (GJA1; Figure S10), pacemaker channels (HCN2 and HCN4; Figure S4), potassium channels (KCND3 and KCNH2; Figure S6), calcium cycling (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 and JPH2; Figure S8), and metabolism (PPARGC1A; Figure S9).