Inflammatory degranulation of the cardiac resident mast cells suppresses the pacemaking and affects activation pattern in the sinoatrial node

•Dominant cardiac pacemaker in sinoatrial node (SAN) exhibits markers of resident immunocompetent cells.•The immune responses of different etiology are known to be accompanied with inflammation-induced SAN-derived arrhythmias.•The activation of SAN resident mast cells with C48/80 significantly affected tissue electrophysiology of cardiac pacemaker.•The degranulation of resident mast cells causes shift of dominant pacemaker site and induces inexcitable zones in the SAN.•The activation of resident mast cells can be considered as a new mechanism of inflammatory induced SAN-derived arrhythmias.