A Clinicopathologic Study on Sick Sinus Syndrome with Histological Approach to the Sinoatrial Node : Symposium on Sinus Node Function and Its Abnormality

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Abstract
Cases (22 patients) with SSS [sick sinus syndrome] were analyzed. Numerical decrease of the sino-atrial node (SAN) cells [SANC] in cases of SSS was definite in 1/2 of cases and a part of cases could be explained by the perinodal lesions or involvement of the autonomic nervous system. Microscopic examination revealed no significant changes in the nerve cells nor ganglion cells. Quantitative measurement of the SANC was an important problem for studying SSS. The aging changes in the SAN and internodal tracts and a decrease of SANC were revealed by visual assessment. A pilot study on a quantitative method by image analyzing computer revealed marked decrease of the SANC/SAN ratio in cases of SSS. The AV [atrioventricular] conduction system revealed lesions at the branching portion of the AV bundle in 3 cases, indicating the portion of conduction block, not the site of automaticity. There were no abnormalities at the AV node and the penetrating portion of the AV bundle, the site of subsidiary pacemaker. Depression of the subsidiary pacemaker in SSS could not be explained by these histological findings of AV conduction system.