Citation: BMJ Case Reports. 13(7), 2020 Jul 28..Journal: BMJ case reports.Published: ; 2020ISSN: 1757-790X.Full author list: Masson R; Bakhshi H; Haddad TM.UI/PMID: 32723779.Subject(s): IN PROCESS -- NOT YET INDEXEDInstitution(s): MedStar Washington Hospital CenterDepartment(s): Medicine/Internal MedicineActivity type: Journal Article.Medline article type(s): Journal ArticleOnline resources: Click here to access onlineDigital Object Identifier: https://dx.doi.org/10.1136/bcr-2020-236009 (Click here)Abbreviated citation: BMJ Case Rep. 13(7), 2020 Jul 28.Abstract: A 70-year-old woman with HER2+/ER+ breast cancer on adjuvant trastuzumab therapy without a history of cardiovascular disease presented with respiratory failure from influenza and was found to have intermittent left bundle branch block (LBBB) with new onset systolic heart failure. Her course was complicated by polymorphic ventricular tachycardia and recurrent chest pain. Significant investigations included a normal cardiac MRI and cardiac catheterisation with unobstructed coronaries. It was determined that the aetiology of her heart failure was trastuzumab-induced cardiotoxicity after comprehensive workup. This case highlights an uncommon presentation of LBBB and the steps taken to diagnose a rare cardiomyopathy. Copyright (c) BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.