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Challenges Challen ges in Clinica Clinicall Electro Electrocardiog cardiograph raphy y
A Case of Ventricular Arrhythmia When Wh en th the e Rig ight ht Is Isn n’t Rig ight ht Shing Shi ng Ch Ching ing,, MBB MBBS;Chiu S;Chiu SunYue SunYue,, MBB MBBS,MRCP S,MRCP
A woman in her 60s presented 60s presented to the emergency department with palpitation and dyspnea. She had multiple syncopal episodes months prior. prior. Her blood pressure was 154/78 mm Hg, her pulse was 184 beats per minute, and her arterial oxygen saturation Video at was98% brea breathi thing ng ambi ambientair. entair. jamainternalmedicine.com jamainternalmedicine. com Her electrocardiogram (ECG) is shown (Figure (Figure 1A). 1A). The arrhythmia did not respond to adenosine. Following amiodarone infusion, a second ECG test was performed (Figure 1B). Questions: What is the cause of the arrhythmia? Does this patient need an implantable cardioverter-defibrillator cardioverter-defibrillator (ICD)?
Interpretation Interpreta tion and Clini Clinical cal Cours Course e The first ECG (Figure 1A) shows a regular wide-complex tachycardia.. “Bu dia “Bumps mps”” tha thatt arevari arevariabl ably y rel relate ated d toQRS com comple plexes xes,, bes bestt see seen n in lead V1, are P waves marching through the tachycardia, indicatindicatingatrioventric ingatriove ntriculardissocia ulardissociation(Figure1A, tion(Figure1A, redarrowheads redarrowheads). ). TheQRS of a dif differ ferentmorp entmorphol hologyat ogyat th the e rig right ht sid side e of thestri thestrip, p, oc occur currin ring g at
an expected interval from the previous beat, and preceded by a P wave wav e (Fig (Figure ure 1A),is a fusio fusion n beat.This ECGis diag diagnost nostic ic of vent ventricuriculartachycardia(VT). lartachyca rdia(VT). Thetachyc Thetachycardiahas ardiahas a left left-bund -bundle le bran branch ch block (LBBB) (LB BB) pat patter tern, n, an inf inferi erior or axi axiss an and d pre predom domina inant nt R in lea lead d 1, pro probbably origi originati nating ng from rightventricul rightventricular ar outf outflow low trac tractt (RV (RVOT). OT). Thepatientwas pharma pharmacolog cologicall ically y cardio cardiovertedto vertedto sinusrhythm (Figure1B). (Fi gure1B). Thi Thiss EC ECG G is a clueto theetiolo theetiology gy of thearrhyt thearrhythmi hmia. a. Firs First, t, followingeachRSR′complexinleadV1 are lowlow-amplit amplitude ude depola depolarizarizationsthat tio nsthat areepsilo areepsilon n wav waves,a es,a fea featur ture e of fra fragme gmente nted d RVconduc RVconductio tion n (Figure 2). 2). A corollary of the same phenomenon is terminal activation ti on de dela lay y, wh whic ich h is ta take ken n fr from om th the e na nadi dirr of th the e S wa wave ve to th the e en end d of all depolarization before the T wave. It is prolonged at 90 milliseconds (normal being < 55 milliseconds). Second, T waves are inverte ve rted d inlead inleadss V1 to V5. Th Thus,thi us,thiss pat patien ientt me meets2 ets2 ma majo jorr an and d 1 min minor or criteriaof arrythmo arrythmogenic genic right ventri ventricular cular cardiom cardiomyopath yopathy y (ARV (ARVC) C)1: (1) epsilon wave in right precordial leads; (2) inverted T waves beyondV3;and(3)sustainedVTofanLBBBmorphologyandinferioraxis. The patient’s coronary angiogram showed only minor irregularities. Transthoracic Transthoracic echocardiographic findings revealed dilated
Figure Figur e 1. Pati PatientElectroc entElectrocardio ardiogram gramss A
Initial electrocardiogram V1
aVR
V4
V2 aVL
I
V5
V3 II
aVF V6
B
Electrocardiogram following pharmacologic cardioversion
I
II
III
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aVR
V1
V4
V2
V5
V3
V6
aVL
aVF
A, Init Initial ial elect electrocard rocardiogra iogram m showi showing ng regular wide-complextachycardia withleft bundl bundle-br e-branchblock anchblock morphologyand morph ologyand infer inferior ior axis.P-wa axis.P-waves ves marchthroughthe QRSindicativ QRSindicative e of atrioventricular dissociation (red arrowhead).A arrowh ead).A fusionbeat (sta (star) r) is notedat not edat th the e rig rightsideof htsideof thestr thestrip ip precededby prece dedby a PP-wave(black wave(black arrowhead); B, Electrocardiogram following pharmacologic cardiovers cardio version.QRS ion.QRS in V1 appears fragmente fragm ented. d. NoteT waveinversi waveinversion on in leadsV lea dsV 1 to V5.
(Reprinted) JAMA Inter Internal nal Medic Medicine ine Publishedonline May 31, 2016
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Clinical Review& Education Challenges in Clinical Electrocardiography
RV, areasof dyskinesiaandthinningover RVfreewall,dilatedRV outflow tract, depressed left ventricular (LV) ejection fraction, and LV posterolateral wall thinning (Figure 3, Video1, 2, and 3), thereby meeting 1 more major criteria of ARVC 1: regional RV akinesia and RVOT dilation.Cardiacmagnetic resonance(CMR)imagingwas not performed because of a metallic hipimplant. The patient was diagnosed as having ARVC after meeting 3 major and 1 minor criteria, and received an ICD for secondary prevention. She continued to experience VT terminated by antitachycardia pacing and shocks. The addition of amiodarone to her treatment led to significant improvement. Genetic testing did not show pathogenic mutations. No other family members have symptoms.
Figure2. EnlargedViewof Lead V1
TAD
Enlarged view of lead V1. Note that this is notrightbundle-branch block.Black arrowhead pointsto theepsilon wave. Terminalactivationdelay (TAD), taken fromnadirof theS wave to theendof alldepolarization beforethe T wave, is prolonged at 90 milliseconds(normal being < 55milliseconds).
Discussion Arrhythmogenicright ventricularcardiomyopathyis aninheritablecardiomyopathy characterized by progressivefibrofatty replacementof
Figure 3. TransthoracicEchocardiogram A
Parasternal short axis
B
Parasternal long axis
C
Subcostal four-chamber
D
Tricuspid valve systolic gradient
A, Parasternal short axis view atthe aortic valvelevelshowinga dilated RVoutflow tract;B, dilatedproximal RVoutflow tractshownin parasternal long axis view; C, subcostal four-chamber view demonstrating RV freewall akinesia and thinning (white arrowhead);D, normalpeak tricuspid regurgitationvelocityindicating absence of significantpulmonary hypertension.
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Challenges in Clinical Electrocardiography ClinicalReview & Education
right, or both ventricular walls,causedby mutationsof desmosomal proteinsthatareidentifiedinabouthalfofcases.Arrhythmogenicright ventricularcardiomyopathy preferentiallyaffects the subtricuspidtriangle,bordered by theRV freewall,apex,and outflowtract,2 resultinginRV freewall dyskinesia andRVoutflowtractdilation.It mayalso involve theposterior andlateralwallsof theLVwhilesparingtheseptum. These features canbe subtle on echocardiographic results, becomingmore apparent in advanced disease. Cardiac magnetic resonance imaging enables quantification of RV function, and characterizationof RV fatand fibrosis, but is notto be usedwithout caveats. For example, thepresence ofadipose tissuein theRV wall is not always pathological; normal RV wall motion can appear dyssynchronousanddifficulttodistinguishfromearlydisease.2 Indeed,CMR findings aremore oftenoverread,and echocardiographicfindingsare more often underread forARVC.3 The scarred RV conducts more slowly and has abnormal repolarization,giving rise to epsilonwavesand rightprecordial T-wave inversion. Terminal activation delay, a signature of slow RV conduction,identifiesARVCwith goodsensitivity,1 especiallybecauseepsilon wavesare present only in1% to9% ofnewlydiagnosedpatients.In advanceddisease,epsilonwavesare moreprevalent, associated with poorer RV functionand higher risk for ventricular arrhythmias.4 Electrical instability is a hallmark of ARVC that may predate RV dysfunction.Most commonly VT is monophormic,has an LBBBmorphology,asuperior,inferior,orundeterminedaxis,andmaymimicidiopathic RVOT VT. The differentiation is important because ARVC is potentially fatal and is not cured by radiofrequencyablation. T-wave inversion in leads V1 to V3 in sinus rhythm is more common in ARVC and more rare in idiopathic RVOT VT; it is specificbut notsensitive.5 Therefore, further diagnostic tests may be necessary for individuals with“red flags,” including family history of sudden death and recurrent VT. ARVC is diagnosed by a constellation of clinical, electrocardiographic, and imaging findings as outlined in therevised TaskForce
Criteria.1 They are grouped under the headings of RV dysfunction, tissue characterization of RV wallon endomyocardial biopsy, repolarization abnormalities, depolarization abnormalities, arrhythmias, and family history, each describing a set of major and minor criteria.Depending on thecriteriafulfilled, thediagnosis is deemed definite,borderline, orpossible. Patients suspectedof havingARVC may have less pronounced RV dysfunction that may not meet imagingcriteria.It isimportantto consider other tests that maycontribute to diagnosis, including signal-averaged ECG, Holter monitoring, and genetic testing. ARVC is associated with ventricular arrhythmia and sudden death.Abortedsuddencardiacdeath,sustained VT, andsevere ventricular dysfunction define a high-riskpopulation in whom ICDimplantation is beneficial. 6 Since arrhythmias may be adrenergically mediated, allpatientsare advisedagainststrenuousexerciseandreceive a β blocker. Nevertheless, some maycontinue to experience VT, requiring treatmentwith anti-arrhythmic drugs.
Take-Home Points • ARVC causes syncope, ventricular arrhythmias, and sudden cardiac death. • Epsilon waves are present in onlya minority of patients.Terminal activation delayis a moresensitive ECGmarker of RV fragmented conduction. • ARVCis diagnosedby demonstratinga constellationof clinical,electrocardiographic, imaging, and tissue findings outlined in the revised Task Force Criteria. • Overreliance on imaging may result in overdiagnosis or underdiagnosis.Otherclinicalaspects haveto be considered, includingECG, family history, and morphology of arrhythmia. • Strenuous exercise is contraindicated. All patients should receive a β-blocker, and ICD for high risk individuals. Family screening should be offered to confirmed cases.
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REFERENCES
Author Affiliations: Division of Cardiology, Departmentof Medicine and Geriatrics, United Christian Hospital, HongKong, China.
1. MarcusFI, McKenna WJ, Sherrill D,et al. Diagnosis of arrhythmogenic rightventricular cardiomyopathy/dysplasia: proposed modification of thetaskforcecriteria. Circulation. 2010;121(13): 1533-1541.
Corresponding Author: ShingChing, MBBS, Departmentof Medicine and Geriatrics, United Christian Hospital, Hip Wo Street, KwunTong,Hong Kong,China(
[email protected]). Section Editors: Zachary D. Goldberger, MD,MS; Nora Goldschlager,MD; Elsayed Z. Soliman, MD, MSc, MS. Published Online: May31, 2016. doi:10.1001/jamainternmed.2016.1982. Conflict of Interest Disclosures: Nonereported.
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2. Te RieleAS, Tandri H,Sanborn DM, BluemkeDA. Noninvasive MultimodalityImagingin ARVD/C. JACCCardiovasc Imaging. 2015;8(5):597-611. 3. Marcus FI,Zareba W, Calkins H,et al. Arrhythmogenic rightventricular cardiomyopathy/dysplasia clinical presentation and diagnosticevaluation: results from the North American Multidisciplinary Study. HeartRhythm. 2009;6(7):984-992.
4. MarcusFI. EpsilonWaves Aidin thePrognosis and RiskStratification of Patients WithARVC/D. J CardiovascElectrophysiol . 2015.doi:10.1111/jce.12775. 5. MorinDP, Mauer AC,GearK, etal. Usefulnessof precordial T-wave inversion to distinguish arrhythmogenic rightventricular cardiomyopathy from idiopathic ventriculartachycardia arisingfrom the rightventricular outflowtract. Am J Cardiol . 2010;105(12):1821-1824. 6. CorradoD, Wichter T, Link MS,et al.Treatment of arrhythmogenic rightventricular cardiomyopathy/dysplasia: an international task forceconsensusstatement. EurHeart J . 2015;36 (46):3227-3237.
(Reprinted) JAMA Internal Medicine Publishedonline May 31, 2016
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