Idorsia Pharmaceuticals 1 article published in JoVE Medicine Contractions of Human-iPSC-derived Cardiomyocyte Syncytia Measured with a Ca-sensitive Fluorescent Dye in Temperature-controlled 384-well Plates Camille Forny1, Romain Sube1, Eric A. Ertel1 1Department of Pharmacology and Preclinical Development, Idorsia Pharmaceuticals Ltd Spontaneously contracting syncytia of cardiomyocytes derived from human-induced pluripotent stem cells are useful models of human cardiac physiology and pharmacology. Here we present a high-throughput screening system to quantify the effects of exogenous compounds on beating frequency, using a Ca-sensitive fluorescent dye and a temperature-controlled imaging multi-well plate reader.