PRKG1 and hydrops fetalis: Notably, reduced PKG activity associated with decreased cGMP levels has been observed across a spectrum of heart diseases in both humans and animal models, including HF with preserved ejection fraction (HFpEF), hypertrophic cardiomyopathy, myocardial infarction-induced HF with reduced LV ejection fraction (HFrEF), and AS [13–19].