PDE5A and heart failure: However, the treatment of heart failure with inhibitors of PDE5 [15] is not based on PDE5 expression in the vasculature, but rather on the abundant expression of PDE5 in cardiomyocytes, and further, the beneficial effects on hypertrophy and heart failure are said to be due to the inhibition of PDE5 in cardiomyocytes [7–10,33].