I’m surprised that no one has brought up the study on the genetically altered pig heart that was transplanted into the late stage, non-compliant, heart failure patient. Study results showed alteration of the normal pig conduction into a more human-like conduction pattern. The way that I read it, it was taken that they had concerns about prolonging of the PR, QRS (as I recall), and specifically the QT intervals. I saw it as an adaptation to more human conduction parameters (pigs have shorter PR, QRS, and QT intervals apparently). I took it as a positive, aside from the QT prolongation (up around .5 sec. as I recall).