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Disappearance of the 2:1 atrioventricular block and QTc shortening (from 740 ms<jats:sup>1\/2<\/jats:sup> to 480 ms<jats:sup>1\/2<\/jats:sup>), however, was achieved when mexiletine was added to propranolol. This effect was considered to be possibly genotype related. Early onset forms of long QT syndrome may benefit from advanced genotyping.<\/jats:p>","DOI":"10.1136\/heart.90.1.13","type":"journal-article","created":{"date-parts":[[2003,12,15]],"date-time":"2003-12-15T18:08:03Z","timestamp":1071511683000},"page":"13-16","source":"Crossref","is-referenced-by-count":44,"title":["Long QT syndrome and life threatening arrhythmia in a newborn: molecular diagnosis and treatment response"],"prefix":"10.1136","volume":"90","author":[{"given":"E","family":"Schulze-Bahr","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H","family":"Fenge","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"D","family":"Etzrodt","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"W","family":"Haverkamp","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"G","family":"M\u00f6nnig","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H","family":"Wedekind","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"G","family":"Breithardt","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H-G","family":"Kehl","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2003,12,15]]},"reference":[{"key":"2025092002082047000_90.1.13.1","unstructured":"Schwartz PJ, Priori SG, Napolitano C. 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