CYP2D6 and heart failure: Using immunoblotting techniques, Zeldin's group reported in 1996 that CYP2J2 was highly expressed in human heart tissues.[11] Their study was followed by Thum and Borlak's study using RT-PCR, which suggested that several CYP450s were expressed in the human heart.[10] Drawing on data obtained from 7 explanted hearts from heart failure patients and 2 hearts from normal subjects, they reported that the presence of CYP1A1, CYP2B6, CYP2C8, CYP2C19, CYP2D6 and CYP4B1 mRNAs.