A clinicopathological study on the sick sinus syndrome

Area of Science:

• Cardiology
• Electrophysiology
• Pathology

Background:

• Sick sinus syndrome (SSS) encompasses various cardiac arrhythmias originating from the sinoatrial node.
• Common SSS manifestations include sinoatrial (SA) block and bradycardia-tachycardia syndrome.
• Understanding the underlying pathology of SSS is crucial for patient management.

Purpose of the Study:

• To investigate the clinical presentation and histopathological findings in patients with sick sinus syndrome.
• To correlate electrophysiological data with structural changes in the SA node and AV conduction system.

Main Methods:

• Retrospective analysis of 6 sick sinus syndrome cases (2 SA block, 4 bradycardia-tachycardia).
• Inclusion of clinical data, electrophysiological studies (including overdrive suppression and AV conduction assessment), and detailed histopathological examination of the SA node and AV conduction system.
• Assessment of SA nodal muscle fiber percentage, connective tissue proliferation, and fibrosis in the left bundle branch.

Main Results:

• Histological findings included a 70-80% reduction in SA nodal muscle fibers, moderate to marked connective tissue proliferation in the SA node, and moderate fibrosis in the left bundle branch.
• Electrophysiological studies showed positive overdrive suppression in 1 case and normal atrioventricular (AV) conduction in 3 cases.
• Clinical outcomes included syncopal attacks in 4 cases and sudden death in 2 cases.

Conclusions:

• Significant histopathological changes, including myocyte loss and fibrosis, characterize sick sinus syndrome.
• These structural alterations likely contribute to the observed clinical symptoms such as syncope and potentially sudden death.
• The SA node artery remained patent, suggesting the pathology is intrinsic to the node and conduction system rather than ischemic.