{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,7]],"date-time":"2025-11-07T09:39:34Z","timestamp":1762508374173,"version":"build-2065373602"},"reference-count":16,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2021,1,6]],"date-time":"2021-01-06T00:00:00Z","timestamp":1609891200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Patients with Brugada syndrome (BrS) can show a leftward deviation of the frontal QRS-axis upon provocation with sodium channel blockers. The cause of this axis change is unclear. In this study, we aimed to determine (1) the prevalence of this left axis deviation and (2) to evaluate its cause, using the insights that could be derived from vectorcardiograms. Hence, from a large cohort of patients who underwent ajmaline provocation testing (n = 1430), we selected patients in whom a type-1 BrS-ECG was evoked (n = 345). Depolarization and repolarization parameters were analyzed for reconstructed vectorcardiograms and were compared between patients with and without a &gt;30\u00b0 leftward axis shift. We found (1) that the prevalence of a left axis deviation during provocation testing was 18% and (2) that this left axis deviation was not explained by terminal conduction slowing in the right ventricular outflow tract (4th QRS-loop quartile: +17 \u00b1 14 ms versus +13 \u00b1 15 ms, nonsignificant) but was associated with a more proximal conduction slowing (1st QRS-loop quartile: +12[8;18] ms versus +8[4;12] ms, p &lt; 0.001 and 3rd QRS-loop quartile: +12 \u00b1 10 ms versus +5 \u00b1 7 ms, p &lt; 0.001). There was no important heterogeneity of the action potential morphology (no difference in the ventricular gradient), but a left axis deviation did result in a discordant repolarization (spatial QRS-T angle: 122[59;147]\u00b0 versus 44[25;91]\u00b0, p &lt; 0.001). Thus, although the development of the type-1 BrS-ECG is characterized by a terminal conduction delay in the right ventricle, BrS-patients with a left axis deviation upon sodium channel blocker provocation have an additional proximal conduction slowing, which is associated with a subsequent discordant repolarization. Whether this has implications for risk stratification is still undetermined.<\/jats:p>","DOI":"10.3390\/ijms22020484","type":"journal-article","created":{"date-parts":[[2021,1,6]],"date-time":"2021-01-06T09:15:16Z","timestamp":1609924516000},"page":"484","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Left Axis Deviation in Brugada Syndrome: Vectorcardiographic Evaluation during Ajmaline Provocation Testing Reveals Additional Depolarization Abnormalities"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2565-337X","authenticated-orcid":false,"given":"Martijn H.","family":"van der Ree","sequence":"first","affiliation":[{"name":"Heart Center, Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jeroen","family":"Vendrik","sequence":"additional","affiliation":[{"name":"Heart Center, Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jan A.","family":"Kors","sequence":"additional","affiliation":[{"name":"Department of Medical Informatics, Erasmus MC, University Medical Center Rotterdam, Doctor Molewaterplein 40, 3015 GD Rotterdam, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ahmad S.","family":"Amin","sequence":"additional","affiliation":[{"name":"Heart Center, Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0528-0852","authenticated-orcid":false,"given":"Arthur A. M.","family":"Wilde","sequence":"additional","affiliation":[{"name":"Heart Center, Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hanno L.","family":"Tan","sequence":"additional","affiliation":[{"name":"Heart Center, Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands"},{"name":"Netherlands Heart Institute, Moreelsepark 1, 3511 EP Utrecht, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2863-9159","authenticated-orcid":false,"given":"Pieter G.","family":"Postema","sequence":"additional","affiliation":[{"name":"Heart Center, Department of Clinical and Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Cardiovascular Sciences, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,6]]},"reference":[{"key":"ref_1","first-page":"665","article-title":"J-Wave syndromes expert consensus conference report: Emerging concepts and gaps in knowledge","volume":"13","author":"Antzelevitch","year":"2016","journal-title":"Europace"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1624","DOI":"10.1016\/j.jacc.2003.06.004","article-title":"Ventricular Arrhythmia Induced by Sodium Channel Blocker in Patients with Brugada Syndrome","volume":"42","author":"Morita","year":"2003","journal-title":"J. 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