PLN and hydrops fetalis: Additionally, the inotropic response to beta-adrenergic stimulation is either absent or nearly absent in both PLN-KO and PLN-R14del cardiomyocytes.26,27 However, while PLN-KO mice are viable and age normally up to 24 months,28 PLN-R14Δ/Δ mice develop severe HF within 8 weeks after birth.