ECG Challenge: AV Block or Something Else?

HomeCirculationVol. 147, No. 3ECG Challenge: AV Block or Something Else? Free AccessCase ReportPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessCase ReportPDF/EPUBECG Challenge: AV Block or Something Else? Leila Haghighat, MD, MPhil, Nora Goldschlager, MD and Adam Oesterle, MD Leila HaghighatLeila Haghighat https://orcid.org/0000-0002-7857-0789 Division of Cardiology (L.H.), Department of Medicine, University of California, San Francisco. Search for more papers by this author , Nora GoldschlagerNora Goldschlager Section of Cardiac Electrophysiology (N.G., A.O.), Department of Medicine, University of California, San Francisco. Division of Cardiology, Department of Medicine, Zuckerberg San Francisco General Hospital, CA (N.G.). Search for more papers by this author and Adam OesterleAdam Oesterle Correspondence to: Adam Oesterle, MD, 4150 Clement St, Bldg 203, Room 2A-25, San Francisco, CA 94121. Email E-mail Address: [email protected] https://orcid.org/0000-0003-1847-8662 Section of Cardiac Electrophysiology (N.G., A.O.), Department of Medicine, University of California, San Francisco. Division of Cardiology, Department of Medicine, San Francisco Veterans Affairs Health Care System, CA (A.O.). Search for more papers by this author Originally published17 Jan 2023https://doi.org/10.1161/CIRCULATIONAHA.122.063243Circulation. 2023;147:267–270ECG ChallengeAn 88-year-old man presented to the emergency department with presyncope. He had previously undergone placement of a dual-chamber pacemaker for atrioventricular block. The device was programmed dual-chamber antibradycardia pacing (DDD) with base rate 60 beats per minute (bpm) and dynamic atrioventricular delay, a parameter in which the atrioventricular delay changes in response to the native atrial heart rate. Medications did not include atrioventricular nodal blocking agents. In the emergency department, blood pressure was 105/70, heart rate 85 beats per minute, temperature 96.9°F, and oxygen saturation 99% at room air. Physical examination was unremarkable. Laboratory evaluation was notable for normal electrolytes and brain natriuretic peptide of 673 pg/mL (normal <100 pg/mL). A 12-lead ECG was obtained (Figure 1).Download figureDownload PowerPointFigure 1. Twelve-lead ECG obtained on arrival to emergency department.What is the rhythm? What are possible explanations for this rhythm, and which is most likely?Please turn the page to read the diagnosis.Response to ECG ChallengeThe ECG demonstrates sinus rhythm with ventricular rate of 81 bpm and a regular, wide-complex QRS rhythm with atrioventricular dissociation, indicated by independent atrial and ventricular activity and absence of fusion or capture beats (Figure 2). Possible explanations include sinus rhythm with atrioventricular block and no evidence of expected pacemaker tracking, accelerated idioventricular ventricular rhythm, junctional rhythm with left bundle branch (BB) aberrancy, and BB reentrant ventricular rhythm.Download figureDownload PowerPointFigure 2. Wide-complex rhythm with atrioventricular dissociation. Black arrows indicate P waves at a regular, independent rate of 71 beats per minute (bpm; with sinus arrhythmia) that is distinct from the QRS rate of 81 bpm. Blue bar indicates the P-P interval (840 ms). Orange bar indicates the R-R interval (740 ms). Retrograde ventriculoatrial conduction is not observed. Slight variation in QRS morphology was considered to be a result of differential activation of right bundle branch fibers.Atrioventricular block involves interruption of impulse transmission from the atria to the ventricles. Atrioventricular block cannot be diagnosed when the native ventricular rate exceeds the pacemaker base rate, because ventricular sensing of the faster ventricular rate inhibits stimulus delivery, as in this patient.Idioventricular ventricular rhythm is an ectopic rhythm of at least 3 consecutive beats that originates from ventricular myocardium because of abnormal automaticity. Idioventricular ventricular rhythm is seen in reperfusion, β-agonist use, cardiomyopathy, and as an incidental finding. Idioventricular ventricular rhythm typically has a QRS morphology that is different from native QRS morphology; in this patient, the native QRS morphology was similar to that of the presenting rhythm (Figure 3).Download figureDownload PowerPointFigure 3. Twelve-lead ECG before pacemaker implantation.BB reentrant ventricular rhythm involves antegrade conduction down 1 BB and retrograde conduction in the other. It occurs in patients with structural heart disease and at rapid rates (200–300 bpm) because the arrhythmia circuit uses the interventricular conduction system.1 The patient’s most likely presenting rhythm is therefore a junctional rhythm with left BB aberrancy.Junctional rhythms are typically a result of enhanced automaticity. Overdrive pacing, which involves delivering pacing stimuli exceeding the native rate, was performed from the RV lead (Figure 4). Overdrive pacing resulted in transient arrhythmia suppression (Figure 5), which can be consistent with an automatic mechanism. However, a reentrant mechanism such as slow atrioventricular nodal reentrant tachycardia with upper common pathway block cannot be excluded.2 An atypical, slower BB reentrant rhythm was excluded by a long difference between the time from cessation of overdrive pacing to the local resumption of native rhythm and the tachycardia cycle length (>30 ms) (Figure 4).3 After initiation of amiodarone, the arrhythmia was no longer seen, and expected DDD function was restored. The patient had no further episodes of presyncope.Download figureDownload PowerPointFigure 4. Electrogram obtained from the patient’s device at the termination of overdrive pacing. The blue bracket (1016 ms) is the time from the last paced electrical signal to the local resumption of the native rhythm. The orange bracket (817 ms) is the tachycardia cycle length (TCL), the time difference between 2 consecutive native electrical ventricular signals. The difference of the time from cessation of pacing to local resumption of native rhythm and TCL is 1016 ms – 817 ms = 199 ms. A difference exceeding 30 ms excludes bundle branch reentry.Download figureDownload PowerPointFigure 5. Twelve-lead ECG during onset and termination of overdrive pacing. The single blue asterisk denotes native interventricular conduction. The double blue asterisk denotes fusion between spontaneous and paced QRS. The triple blue asterisk denotes the first fully paced QRS complex. This ECG correlates with the intracardiac electrogram from Figure 4, with blue bracket indicating termination of overdrive pacing and return of the arrhythmia, and the orange bracket denoting the tachycardia cycle length.Article InformationSources of FundingNone.Disclosures None.FootnotesFor Sources of Funding and Disclosures, see page 270.Circulation is available at www.ahajournals.org/journal/circCorrespondence to: Adam Oesterle, MD, 4150 Clement St, Bldg 203, Room 2A-25, San Francisco, CA 94121. Email adam.[email protected]eduReferences1. Caceres J, Jazayeri M, McKinnie J, Avitall B, Denker ST, Tchou P, Akhtar M. Sustained bundle branch reentry as a mechanism of clinical tachycardia.Circulation. 1989; 79:256–270. doi: 10.1161/01.cir.79.2.256LinkGoogle Scholar2. Tenczer J, Littmann L, Rohla M, Fenyvesi T. The effects of overdrive pacing and lidocaine on atrioventricular junction rhythm in man: the role of abnormal automaticity.Circulation. 1985; 72:480–486. doi: 10.1161/01.cir.72.3.480LinkGoogle Scholar3. Merino JL, Peinado R, Fernandez-Lozano I, Lopez-Gil M, Arribas F, Ramirez LJ, Echeverria IJ, Sobrino JA. Bundle-branch reentry and the postpacing interval after entrainment by right ventricular apex stimulation: a new approach to elucidate the mechanism of wide-QRS-complex tachycardia with atrioventricular dissociation.Circulation. 2001; 103:1102–1108. doi: 10.1161/01.cir.103.8.1102LinkGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails January 17, 2023Vol 147, Issue 3 Advertisement Article InformationMetrics © 2023 American Heart Association, Inc.https://doi.org/10.1161/CIRCULATIONAHA.122.063243PMID: 36649396 Originally publishedJanuary 17, 2023 PDF download Advertisement SubjectsArrhythmias