Sinus Node Abnormalities

The sinus node is a crescent-shaped structure with a complex anatomic construct that is well innervated with both adrenergic and cholinergic nerves integral to its cardiac pacemaking function. Abnormality in impulse generation of the sinus node is most commonly due to age-related degenerative disease, although a long list of intrinsic and extrinsic causes is known to affect sinus node function. Sinus node disease is also known to be associated with underlying atrial myopathy. On the other hand, patients with atrial arrhythmias are known to exhibit sinus node dysfunction. Additionally, several mutations in ion channel and structural proteins have been identified to contribute to sinus node dysfunction. The challenge in diagnosing sinus node disease is to correlate symptoms with electrocardiographic documentation as the resting 12-lead electrocardiogram is often normal in most patients. Cardiac pacing is an effective mainstay strategy to increase heart rate and improve symptoms after excluding and treating the potential reversible causes of sinus node disease.