{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T18:59:18Z","timestamp":1785437958976,"version":"3.56.0"},"reference-count":15,"publisher":"Oxford University Press (OUP)","issue":"7","license":[{"start":{"date-parts":[[2026,7,20]],"date-time":"2026-07-20T00:00:00Z","timestamp":1784505600000},"content-version":"vor","delay-in-days":19,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,7,2]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>His-bundle pacing (HBP) enables physiological ventricular activation and has been associated with superior clinical outcomes compared with conventional pacing. Nevertheless, chronic threshold elevation remains a major limitation, often leading to early battery depletion or lead revision. The pathological mechanisms underlying chronic threshold elevation have not been fully elucidated.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case summary<\/jats:title>\n                    <jats:p>A 76-year-old man with symptomatic 2:1 atrioventricular block underwent successful HBP implantation, achieving selective His-bundle capture. One week after implantation, both His-bundle and right ventricular pacing thresholds increased markedly. Although the His-bundle capture threshold transiently improved during follow-up, it deteriorated again by 1 year and stabilized. After 5 years and 5 months, early battery depletion prompted extraction of the ventricular lead and re-implantation using left bundle branch pacing. Histopathological examination of the extracted lead tip revealed fibrin-rich tissue with fibroblast proliferation and CD31-positive microvessels. Numerous CD68-positive macrophages were present at the lead\u2013tissue interface. No myocardial or conduction system tissue was identified, which may be consistent with development of a physical barrier between the lead tip and the His-bundle.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion<\/jats:title>\n                    <jats:p>This case raises the hypothesis that early fibrin deposition followed by organization may contribute to chronic HBP threshold elevation by increasing the separation between the lead tip and the His-bundle. We speculated that fibrotic tissue interposed between the screw and the His-bundle progressively enlarged, leading to micro-dislodgement and subsequent threshold elevation. To our knowledge, this is one of the first reports describing the histopathological findings of a case with chronic threshold deterioration following HBP.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1093\/ehjcr\/ytag550","type":"journal-article","created":{"date-parts":[[2026,7,18]],"date-time":"2026-07-18T11:39:28Z","timestamp":1784374768000},"source":"Crossref","is-referenced-by-count":0,"title":["What is the mechanism of chronic threshold elevation after His-bundle pacing? A histopathological case report suggesting the involvement of fibrin fibrosis"],"prefix":"10.1093","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-8709-7557","authenticated-orcid":false,"given":"Kenji","family":"Baba","sequence":"first","affiliation":[{"name":"Department of Cardiovascular Medicine, Bell-land General Hospital , 500-3 Higashiyama, Naka-ku, Sakai, Osaka 599-8247 ,","place":["Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9883-8316","authenticated-orcid":false,"given":"Shogo","family":"Sakamoto","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Medicine, Bell-land General Hospital , 500-3 Higashiyama, Naka-ku, Sakai, Osaka 599-8247 ,","place":["Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Moritoshi","family":"Irishio","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Medicine, Bell-land General Hospital , 500-3 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