Sick sinus syndrome

Sick sinus syndrome (SSS), also called sinus dysfunction (SND), or sinoatrial node disease, is a group of abnormal heart rhythms (arrhythmias) presumably caused by a malfunction of the sinus node, the heart's primary pacemaker. Bradycardia-tachycardia syndrome is a variant of sick sinus syndrome in which slow arrhythmias and fast arrhythmias alternate. It is often associated with ischaemic heart disease and heart valve disease.