The primary finding of our study is that we could not detect PDE5 in tissue homogenates from the LV of mice (normal, compensated hypertrophy or HF, Fig. 1), canines (LV and RV with and without HFpEF, Fig. 2) and human heart samples (normal controls or patients with HF, Fig. 3), while PDE5 was detected as a single band in lysates prepared from the murine and bovine lung used as a positive control. Here, PDE5A is linked to hydrops fetalis.