Relationship between basal thinning of the interventricular septum and atrioventricular block in patients with cardiac sarcoidosis

Background: Basal thinning of the interventricular septum (IVS) and atrioventricular block (AVB) are characteristic features of cardiac sarcoidosis. Since the conduction system passes along IVS, it has been considered that a close connection exists between basal thinning of IVS and AVB. However, neither the incidence of cases showing basal thinning of IVS nor the relation between it and AVB has been clarified. We thus investigated to elucidate these two issues. Methods: Thirty-five patients with cardiac sarcoidosis were selected for this study and underwent echocardiographic examination. The wall thickness of IVS was measured at a site 1 cm below the aortic valve inserted point of IVS. Thickness of this site ≤ 5 mm was defined as thinning. Twelve-lead and Holler electrocardiograms were obtained to determine the presence/absence and degree of AVB. Results: Basal thinning of IVS was noted in 7 of the 35 patients (20%). AVB was present in 4 of these 7 (57%), and was first degree in 3 (43%) and third degree in one (14%). AVB was not present in 3 patients. Basal thinning of IVS was not apparent in 28 of the 35 patients (80%). AVB was observed in 14 of the 28 patients, 3 had first degree block, 2 had second degree block, and 9 had third degree block. AVB was not observed in 14 of the 28 patients. Conclusions: These results clarified that basal thinning of IVS is not as common as previously thought in cardiac sarcoidosis, basal thinning of IVS and the presence/absence and degree of AVB are not necessarily correlated.