MUMJ Clinical Quiz 61 CLINICAL QUIZ What Are These ECG Diagnoses? Lucy Lu Figure 1. 43-year-old male with sudden-onset pleuritic chest pain that radiates to the left shoulder and worsens when lying down. Figure 2. 49-year-old obese female with a 6-hour history of dyspnea and dizziness. 62 Clinical Quiz Volume 7 No. 1, 2010 Figure 3. 32-year-old male with palpitations, dizziness and syncope. Figure 4. 69-year-old female, on hemodialysis for 4 years, presents with generalized fatigue, muscle weak - ness, paresthesia and palpitations. MUMJ Clinical Quiz 63 Figure 5. 83-year-old male with palpitations, dyspnea, dizziness and fatigue. Figure 6. 78-year-old male with recurrent pre-syncope and syncope. 64 Clinical Quiz Answers Volume 7 No. 1, 2010 CLINICAL QUIZ ANSWERS figure 1. Diagnosis: Acute Pericarditis figure 5. Diagnosis: Atrial flutter with 2:1 AV Block ThereisdiffuseST-segmentelevationthatisconcave ThisECGdemonstratesanarrowcomplextachycardia,with upwards,withJpointelevation.ThereisalsoPRdepression negativesawtoothcomplexesininferiorleadscharacteristic intheinferiorleadsandPRelevationinaVR.Thisrepresents oftypicalatrialflutter.BymappingthePwavesinleadV1, Stage1of4stagesofECGchangesinacutepericarditis. itcanbeshownthattheatrialrateis300beatsperminute. ThenumberofQRScomplexesindicatestheventricularrate figure 2. Diagnosis: Pulmonary Embolism is150beatsperminute.Thereisa2:1conductionblock, Whenthepulmonaryarteryisseverelyobstructedbylarge sincetheatrioventricularnodecannotconductatthesame pulmonaryemboli,theremayberightheartdysfunction. rateastheatrialactivity. ThisECGdemonstratestherarebutclassicsignsofright ventricularstrain:deepSwaveinleadI,deepQwaveinIII, figure 6. Diagnosis: Bifascicular block and 2:1 AV Block invertedTwaveinIIIandincompleterightbundlebranch ThisECGhasanatrialrateof75beatsperminuteandaven - blockwithST-TchangesinV1-V3.However,itshouldbe tricularrateof30beatsperminute.EveryotherPwaveis notedthatthispatientalsohassinustachycardia,whichis followedbyaQRScomplex,thusthereisa2:1atrioventric - themostcommonECGabnormalityinpulmonary ularblock.Thepresenceofrightbundlebranchblock embolism. (RBBB)isindicatedbyrSR’complexandinvertedTwave inleadV1anddeepSwaveinV6.Thereisalsoaleftante - figure 3. Diagnosis: Wolff-Parkinson-White pre-excita - riorfascicularblock(LAFB),identifiedbyleftaxisdevia - tion syndrome tion,withsmallqandbigRwavesinI,andsmallrwithbig Wolff-Parkinson-White(WPW)syndromeisacongenital SwavesinIII.ThecombinationofRBBBandLAFBis abnormalitythatinvolvesthepre-excitationoftheventricles referredtoasbifascicularblock.Withsuchadvancedcon - throughanatrioventricular(AV)accessorypathwaycalled ductionsystemdiseaseandaslowheartrate,thispatient theBundleofKent.Sincetheelectricimpulsetravels needsapacemaker. throughtheaccessorypathwayandbypassestheAVnode delay,theclassicfindingsofWPWasshowninthisECG ACKNOWLEDGEMENT are:shortPRinterval(<120ms),wideQRScomplexwith ECGsandeditingarecourtesyofDr.RajeevRao,cardiolo - slurredupstrokes(deltawaves),asseenhereinleadsI,aVL gyfellowoftheDivisionofCardiology,Departmentof andtheanteriorprecordialleads. Medicine,MichaelG.DeGrooteSchoolofMedicine, McMasterUniversity. figure 4. Diagnosis: hyperkalemia ThisECGshowssignstypicalofhyperkalemia,including wideQRScomplex,tallpeakedTwaves,prolongedQTand PRintervals,withflattenedanddiminishedPwaves. Hyperkalemiaincreasestheactivityofpotassiumchannels andspeedsupmembranerepolarization,causingtallpeaked Twaves.Italsoslowsimpulseconductionandprolongs depolarization,leadingtosmallPwavesandwidenedQRS complex. Author Biography Lucy Lu is a second-year medical student at the Michael G. DeGroote School of Medicine at McMaster University. She previously studied life sciences at the University of Toronto. .