It has also been reported that up to 33% of patients with DCM produce detectable circulating autoantibodies directed against epitope regions of the β1-AR [16], which bind to the second extracellular loop of β1-AR and cause a sustained stimulation of the cAMP-dependent protein kinase A pathway, and are finally associated with reduced cardiac function in those patients [13]. This evidence concerns the gene ADRB1 and familial dilated cardiomyopathy.