AUTONOMIC REGULATION AND SA NODE DYSFUNCTION

Sick Sinus Syndrome (Sinus Node Dysfunction) Sick sinus syndrome (SSS), also known as sinus node dysfunction, is a group of cardiac rhythm disorders resulting from impaired function of the sinoatrial (SA) node, the heart’s primary pacemaker. It is most commonly observed in elderly individuals and is often associated with degenerative fibrosis of the SA node and surrounding atrial tissue, though it may also arise from ischemic heart disease, cardiomyopathies, congenital abnormalities, or the effects of medications such as beta-blockers and calcium channel blockers. Clinically, SSS is characterized by a spectrum of arrhythmias, including sinus bradycardia, sinus arrest, sinoatrial exit block, and alternating bradyarrhythmias and tachyarrhythmias (tachy-brady syndrome). Symptoms range from asymptomatic presentations to fatigue, dizziness, syncope, palpitations, and heart failure due to reduced cardiac output. Diagnosis relies on electrocardiographic monitoring, often requiring Holter or event recorders to capture intermittent abnormalities. Management focuses on identifying and correcting reversible causes; however, symptomatic patients typically require permanent pacemaker implantation, with adjunctive pharmacologic therapy for associated atrial tachyarrhythmias. Early recognition and appropriate treatment are essential to prevent complications and improve quality of life.