Sinus node disease: an idiopathic right atrial myopathy

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Pathology

Background:

• Sinus node disease was traditionally viewed as localized to the sinus node and atrial connections.
• Emerging evidence redefines sinus node disease as a condition affecting the entire right atrial myocardium.

Purpose of the Study:

• To investigate the extent and nature of electrophysiological and structural abnormalities in sinus node disease.
• To explore the relationship between these changes and the prevalence of atrial fibrillation.

Main Methods:

• Electrophysiological studies assessing refractory periods and conduction velocity.
• Analysis of endocardial signals for fractionated signals, low-voltage electrograms, and electrically silent areas.
• Histopathological examination for fibrosis and fatty infiltration.

Main Results:

• Patients with sinus node disease exhibit widespread atrial electrophysiological abnormalities, including prolonged refractoriness and slowed conduction.
• Significant structural changes like fibrosis and fatty infiltration are present in the right atrial myocardium.
• Endocardial mapping reveals fractionated signals, low-voltage electrograms, and electrically silent regions.

Conclusions:

• Sinus node disease is a diffuse atrial myocardial process, not limited to the sinus node.
• The observed electrical and structural changes likely contribute to the high incidence of atrial fibrillation in these patients.
• The etiology of these widespread changes remains largely unknown.