{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,7]],"date-time":"2026-03-07T10:56:04Z","timestamp":1772880964052,"version":"3.50.1"},"reference-count":39,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2022,10,24]],"date-time":"2022-10-24T00:00:00Z","timestamp":1666569600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>Second-degree atrioventricular (AV) block is the most common cardiac arrhythmia in horses, affecting 40\u201390% depending on breed. Usually, the AV blocks occur while the horses are resting and disappear upon exercise and are, therefore, considered to be uneventful for horses. However, if the AV blocks occur frequently, this may result in syncope and collapse. Identifying the cause of second-degree AV block is difficult and often subscribed to high vagal tone. In this report, we present an eight-year-old Quarter horse with a high burden of second-degree AV blocks and multiple collapses. The clinical examination, including neurological examination, blood analysis, 24-h ECG recording and cardiac echocardiography, did not reveal any signs of general or cardiovascular disease besides a high burden of second-degree AV blocks (~300 blocks per hour) and a hyperechoic area in the AV nodal region. An implantable loop recorder (ILR) was inserted to monitor the cardiac rhythm. The ILR detected several consecutive second-degree AV blocks and pauses above 5 s. However, unfortunately, no recordings were available during the collapses. Eventually, the horse was euthanized and the heart inspected. The aortic root was severely cartilaginous and appeared to penetrate the AV node, especially in the His bundle region, possibly explaining the hampered AV conduction. Nevertheless, it is still uncertain if the AV nodal disruption caused the collapses and more knowledge on AV nodal diseases in horses is warranted.<\/jats:p>","DOI":"10.3390\/ani12212915","type":"journal-article","created":{"date-parts":[[2022,10,24]],"date-time":"2022-10-24T21:09:17Z","timestamp":1666645757000},"page":"2915","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Cartilaginous Intrusion of the Atrioventricular Node in a Quarter Horse with a High Burden of Second-Degree AV Block and Collapse: A Case Report"],"prefix":"10.3390","volume":"12","author":[{"given":"Sarah Dalgas","family":"Nissen","sequence":"first","affiliation":[{"name":"Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, H\u00f8jbakkegaard All\u00e9 5, 2630 Taastrup, Denmark"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Arnela","family":"Saljic","sequence":"additional","affiliation":[{"name":"Institute of Pharmacology, West German Heart and Vascular Centre, University of Duisburg-Essen, 45117 Essen, Germany"},{"name":"Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9828-5494","authenticated-orcid":false,"given":"Sofie Troest","family":"Kjeldsen","sequence":"additional","affiliation":[{"name":"Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, H\u00f8jbakkegaard All\u00e9 5, 2630 Taastrup, Denmark"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Thomas","family":"Jespersen","sequence":"additional","affiliation":[{"name":"Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Charlotte","family":"Hopster-Iversen","sequence":"additional","affiliation":[{"name":"Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, H\u00f8jbakkegaard All\u00e9 5, 2630 Taastrup, Denmark"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8201-0186","authenticated-orcid":false,"given":"Rikke","family":"Buhl","sequence":"additional","affiliation":[{"name":"Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, H\u00f8jbakkegaard All\u00e9 5, 2630 Taastrup, Denmark"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1186\/BF03546937","article-title":"Long term ECG recording with Holter monitoring in clinically healthy horses","volume":"33","author":"Raekallio","year":"1992","journal-title":"Acta Vet. 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