hyperpol. & decr. rate spontaneous depol. at SA node
decr. AV conduction → may cause CHB in XS;
inc. funct. refract. period AV node → decr. vent.resp. to AF
decr. contract.(esp. atrial); decr. duration of AP;
decr. effective refractory period;
if disease or arrhythmia → partial depol. then ⇒ inc. cond. velocity in atrial muscle
decr. automaticity of Purkinje fibres;
inc. threshold for VF;
decr. myocardial response to catecholamines;