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MUMJ
Clinical Quiz
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.
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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 weakness, paresthesia and palpitations.
MUMJ
Clinical Quiz
Figure 5. 83-year-old male with palpitations, dyspnea, dizziness and fatigue.
Figure 6. 78-year-old male with recurrent pre-syncope and syncope.
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Clinical Quiz Answers
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Volume 7 No. 1, 2010
CLINICAL QUIZ ANSWERS
figure 1. Diagnosis: Acute Pericarditis
There is diffuse ST-segment elevation that is concave
upwards,withJpointelevation.ThereisalsoPRdepression
intheinferiorleadsandPRelevationinaVR.Thisrepresents
Stage1of4stagesofECGchangesinacutepericarditis.
figure 2. Diagnosis: Pulmonary Embolism
Whenthepulmonaryarteryisseverelyobstructedbylarge
pulmonary emboli, there may be right heart dysfunction.
This ECG demonstrates the rare but classic signs of right
ventricularstrain:deepSwaveinleadI,deepQwaveinIII,
invertedTwaveinIIIandincompleterightbundlebranch
blockwithST-TchangesinV1-V3.However,itshouldbe
noted that this patient also has sinus tachycardia, which is
the most common ECG abnormality in pulmonary
embolism.
figure 3. Diagnosis: Wolff-Parkinson-White pre-excitation syndrome
Wolff-Parkinson-White (WPW) syndrome is a congenital
abnormalitythatinvolvesthepre-excitationoftheventricles
through an atrioventricular (AV) accessory pathway called
the Bundle of Kent. Since the electric impulse travels
through the accessory pathway and bypasses theAV node
delay, the classic findings of WPW as shown in this ECG
are:shortPRinterval(<120ms),wideQRScomplexwith
slurredupstrokes(deltawaves),asseenhereinleadsI,aVL
andtheanteriorprecordialleads.
figure 5. Diagnosis: Atrial flutter with 2:1 AV Block
ThisECGdemonstratesanarrowcomplextachycardia,with
negativesawtoothcomplexesininferiorleadscharacteristic
oftypicalatrialflutter.BymappingthePwavesinleadV1,
itcanbeshownthattheatrialrateis300beatsperminute.
ThenumberofQRScomplexesindicatestheventricularrate
is 150 beats per minute. There is a 2:1 conduction block,
since the atrioventricular node cannot conduct at the same
rateastheatrialactivity.
figure 6. Diagnosis: Bifascicular block and 2:1 AV Block
ThisECGhasanatrialrateof75beatsperminuteandaventricularrateof30beatsperminute.EveryotherPwaveis
followedbyaQRScomplex,thusthereisa2:1atrioventricular block. The presence of right bundle branch block
(RBBB)isindicatedbyrSR’complexandinvertedTwave
inleadV1anddeepSwaveinV6.Thereisalsoaleftanterior fascicular block (LAFB), identified by left axis deviation,withsmallqandbigRwavesinI,andsmallrwithbig
S waves in III. The combination of RBBB and LAFB is
referred to as bifascicular block.With such advanced conduction system disease and a slow heart rate, this patient
needsapacemaker.
ACKNOWLEDGEMENT
ECGsandeditingarecourtesyofDr.RajeevRao,cardiology fellow of the Division of Cardiology, Department of
Medicine, Michael G. DeGroote School of Medicine,
McMasterUniversity.
figure 4. Diagnosis: hyperkalemia
This ECG shows signs typical of hyperkalemia, including
wideQRScomplex,tallpeakedTwaves,prolongedQTand
PR intervals, with flattened and diminished P waves.
Hyperkalemia increases the activity of potassium channels
andspeedsupmembranerepolarization,causingtallpeaked
T waves. It also slows impulse conduction and prolongs
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.