<b>Background:</b> Atrial dilated cardiomyopathy (ADCM) related to homozygous <i>Natriuretic Peptide Precursor A</i> (<i>NPPA</i>) pathogenic variants is an exceptionally rare inherited atrial cardiomyopathy characterized by progressive atrial enlargement, supraventricular arrhythmias, and eventual atrial standstill. The gene discussed is NPPA; the disease is atrial standstill.