PDE5A and hydrops fetalis: PDE3 inhibitors, such as milrinone and enoximone, are used in acute HF (AHF), and PDE5 inhibitors, such as sildenafil and udenafil, improve contractile function in systolic HF, blunt left ventricular (LV) hypertrophic remodelling, reduce myocardial infarct size, and suppress ventricular arrhythmias [15], although both classes do not ameliorate the outcome of HF patients [16].