Sick sinus syndrome

Sick sinus syndrome (SSS) or sinus node dysfunction (SND) refers to any condition where the SA node is dysfunctional. This causes intermittent sinus bradycardia, sinus pauses (pauses <3 seconds), sinus arrest (pauses >3 seconds), tachycardia-bradycardia syndrome, chronotropic incompetence, or SA block. Patients present with intermittent complaints of fatigue, dizziness, palpitations, syncope, etc.

SSS is usually idiopathic, due to SA node degeneration, but it can also be due to ischaemia or structural cardiac abnormalities like cardiomyopathy. It mostly affects elderly.

Patients often require implantation of a pacemaker.

Tachycardia-bradycardia syndrome

Tachycardia-bradycardia syndrome (sometimes shortened as tachy-brady syndrome) is a form of sick sinus syndrome characterised by alternating sinus bradycardia and sinus tachycardia. Usually several beats are skipped between the alteration from tachy to brady.

The syndrome can cause dizziness, syncope, palpitations, and chest pain. Pacemaker implantation is usually necessary.