Histologic Comparison of Fibrosis in the Sinoatrial Node of Cadavers With and Without Permanent Pacemakers

Background The sinoatrial (SA) node serves as the primary pacemaker of the heart, initiating electrical impulses that regulate normal cardiac rhythm. Age-related structural remodeling of the SA node, particularly fibrosis and increased collagen deposition, has been strongly associated with sinus node dysfunction and represents a leading indication for permanent pacemaker implantation in older adults. Despite this association, limited histologic research has directly compared SA node architecture between individuals with pacemakers and age-matched individuals without pacing devices.

Objective The purpose of this study was to evaluate and compare the degree of fibrosis and collagen deposition within the SA node of cadavers with and without permanent pacemakers.

Methods and Materials SA node tissue was obtained from six cadavers ranging in age from 65 to 92 years, including three individuals with documented pacemaker implantation and three without pacing devices. Tissue samples were processed and stained using hematoxylin and eosin (H&E) to assess general tissue architecture and cellular composition, and Masson’s trichrome staining to evaluate collagen deposition and fibrotic remodeling. Qualitative histologic comparison focused on identifying differences in pacemaker cell density, connective tissue replacement, and overall nodal microarchitecture between the two groups. Particular attention was given to patterns of collagen accumulation and structural disruption that may impair impulse generation and propagation. By examining these histologic features within an aging cohort, this study aims to determine whether individuals with pacemakers demonstrate increased fibrotic remodeling of the SA node compared to those without pacing devices, thereby contributing to a clearer understanding of the structural basis of sinus node dysfunction and pacemaker dependence.