March 26th Question

HomeCirculation: Arrhythmia and ElectrophysiologyVol. 11, No. 4March 26th Question Free AccessArticle CommentaryPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessArticle CommentaryPDF/EPUBMarch 26th Question Pasquale Santangeli, MD, PhD Pasquale SantangeliPasquale Santangeli Originally published26 Mar 2018https://doi.org/10.1161/CIRCEP.118.006297Circulation: Arrhythmia and Electrophysiology. 2018;11:e006297See Answer to March 19th Following QuestionA 42-year-old woman presents with recurrent monomorphic hemodynamically stable ventricular tachycardia (Figure 1) refractory to amiodarone and lidocaine. Pre-procedure cardiac myocardial resonance imaging is normal. Endocardial right ventricle bipolar voltage map is also normal (Figure 2). Response of the ventricular tachycardia to a pacing maneuver delivered from the mapping catheter positioned across the tricuspid valve in the outflow tract, and a fully paced QRS morphology from the same pacing site during sinus rhythm, is shown in Figure 3. What is the mechanism of the ventricular tachycardia?Download figureDownload PowerPointFigure 1. 12-lead electrocardiogram of the ventricular tachycardia.Download figureDownload PowerPointFigure 2. Endocardial right ventricle bipolar voltage map.Left, Right anterior oblique view. Right, Left anterior oblique view.Download figureDownload PowerPointFigure 3. Response of the ventricular tachycardia to pacing from the ablation catheter (CARTO D) positioned at the right ventricular outflow tract. The paced QRS morphology from the same site when pacing in sinus rhythm is available in the right panel.Answer OptionsA. Focal automatic ventricular tachycardiaB. Focal triggered ventricular tachycardiaC. Reentrant ventricular tachycardiaD. Antidromic atrioventricular reentry tachycardiaE. Additional information is requiredANSWER TO MARCH 19th QUESTIONB. Orthodromic atrioventricular reentryExplanationThe ECG in Figure 1 shows sinus P waves marching through the tracing (asterisks). There are 2 narrow QRS complexes, numbers 1 and 2, for every P wave, with slightly varying RR intervals and the QRS morphology (alternans). The PR interval for every other QRS complex is fixed. This suggests that both QRS complexes are coupled to the preceding P wave (red and blue arrows). The narrow configuration of the QRS complexes suggests antegrade activation through the His-Purkinje system and excludes options like myocardial premature ventricular complexes or bundle branch reentry beats that would result in a wide QRS complex.Download figureDownload PowerPointFigure 1. Electrocardiogram. Asterisks depict the marching sinus P waves; each P wave is followed by two narrow QRS complexes 1 and 2.Download figureDownload PowerPointFigure 2. Illustration.(i) through (iv) show the differential diagnosis for electrocardiogram in Figure 1, with two narrow QRS complexes for each regular sinus P wave. AV indicates atrioventricular.QRS complex number 1 after a P wave can be explained by normal atrioventricular conduction (using the fast pathway, atrioventricular node, and the His-Purkinje system). QRS complex number 2 is a bigeminal ectopic beat that is generated without reactivation of the atria (absence of a separate preceding P wave). This excludes atrial ectopy and atrioventricular reentry (Option B), mechanisms that require a P wave to generate a QRS complex. Conversely, the differential diagnosis for QRS number 2 can be any mechanism that can antegradely recruit the His-Purkinje system without preceding atrial activation. As illustrated in Figure 2, this could include (1) dual atrioventricular node physiology with 2 for 1 response over 2 distinct atrionodal connections (Option D), (2) bigeminal atrioventricular junctional ectopy (Option C), (3) bigeminal reentrant beats with retrograde conduction up a nodofascicular/nodoventricular tract and antegrade His-Purkinje activation (Option A), and (4) sequential His-Purkinje system activations over 2 separate atrioventricular conduction systems (AV node duplication or presence of an accessory atrio-Hisian tract; Option E).The alternans in the morphology of QRS numbers 1 and 2 in Figure 1 despite both being derived from antegrade His-Purkinje activation is likely a result of slight relative temporal differences in recruitment of atrioventricular node tissue predetermined for distinct His-Purkinje fibers.Footnoteshttp://circep.ahajournals.org Previous Back to top Next FiguresReferencesRelatedDetails April 2018Vol 11, Issue 4 Advertisement Article InformationMetrics © 2018 American Heart Association, Inc.https://doi.org/10.1161/CIRCEP.118.006297PMID: 29581102 Originally publishedMarch 26, 2018 PDF download Advertisement SubjectsArrhythmiasElectrophysiology