Altogether, decreases in PDE4D activity, which represents the main PDE4 isoform in human cardiac tissue, might favor idiopathic dilated cardiomyopathy and its deficiency in the RyR complex promotes heart failure and arrhythmias, whereas PDE4B prevents Ca2+ overload and arrhythmias. This evidence concerns the gene PDE4A and idiopathic dilated cardiomyopathy.