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A woman in her late 40s with a history of hypertension presented to the emergency department after multiple episodes of palpitations with near syncope. While in the emergency department, she developed monomorphic ventricular tachycardia (VT) with hemodynamic instability and was successfully cardioverted. She continued to have nonsustained monomorphic VT, so intravenous amiodarone and oral metoprolol were initiated. She was admitted for further evaluation. Results of tests of electrolyte levels and coronary angiography were normal. Cardiac magnetic resonance imaging with gadolinium contrast revealed normal-sized cardiac chambers and normal biventricular function without delayed enhancement. The presenting electrocardiogram (ECG) is shown in Figure 1.
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Outflow tract ventricular tachycardia
B. Electrophysiology study with possible catheter ablation
This patient presented with recurrent symptomatic monomorphic VT suggestive of an outflow tract (OT) origin. An electrophysiology (EP) study to anatomically localize the abnormal rhythm and ablation therapy is the preferred strategy in severely symptomatic patients. Medical therapy may be considered; owing to limited and varying efficacy of pharmacologic therapy and its adverse effects, an EP study with ablation, with its high success rate and low complication rate, is preferred. Outflow tract VT (OTVT) is a monomorphic subset of idiopathic VT diagnosed in patients without underlying structural heart disease, metabolic abnormalities, or cardiac channelopathies. Right ventricular OT (RVOT) VT makes up about 80% of OTVT cases, with most originating just inferior to the pulmonic valve from the anterior and superior septal aspects of the RVOT. The other 20% are left ventricular OT (LVOT) VT, which commonly arises from the region of the aortic cusps in the aortic root.1 A surface ECG with an inferior axis, left bundle branch block (BBB) morphology, and precordial R-wave transition at V4 or after suggests RVOT VT, while one with an inferior axis, right or left BBB morphology, and precordial R-wave transition at V2 or earlier suggests LVOT VT.2 Despite surface ECG findings that may differentiate LVOT from RVOT, definitive localization is via electroanatomic mapping in an EP study.
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Corresponding Author: Laith A. Derbas, MD, Division of Medicine, University of Missouri, Kansas City, 2301 Holmes St, Kansas City, MO 64111 (firstname.lastname@example.org).
Published Online: November 7, 2018. doi:10.1001/jamacardio.2018.3687
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Yousuf reports receiving honoraria from Medtronic and Boston Scientific as a part of their speakers’ bureaus and Abbott and Biosense Webster as a consultant. No other disclosures were reported.
Additional Contributions: We thank Alan P. Wimmer, MD, Saint Luke’s Health System, for his manuscript review. He was not compensated.
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