They have a modest hypotensive action and a mildnitrate-like action since PDE-5 is also present in vascular smooth muscle cells.Properly for their mechanisms, initially HF was considered as a relativecontraindication for their use [40] but, subsequently, Katz and colleaguesdemonstrated the safety of this class of drugs in patients with mild to moderateHF [41]. Here, PDE5A is linked to hydrops fetalis.