Dissociation of RV and LV PDE5 expression and an inconsistent relationship between PDE5 and cGKI expression provided further evidence that the signal transduction pathways involving PDE5 during cardiac hypertrophy could be regulated differently in the two chambers, as recently suggested by others commenting on incongruent responses to in vivo PDE5 inhibition [16], [35]. Here, PDE5A is linked to cardiac hypertrophy.