ADRB2 and hydrops fetalis: This finding has been postulated to be part of the mechanism of carvedilol’s beneficial effects in HF [23]; however, it awaits confirmation with in vivo studies specifically on cardiac β2AR, and, once confirmed, it would be interesting to delineate whether carvedilol preferentially stimulates the binding to the cardiac β2ARs (and β1ARs) of one βarr isoform over the other or the binding of both cardiac βarrs is equally induced.