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 andworsens 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.

CLINICAL QUIZ ANSWERS

64 Clinical Quiz Answers Volume 7 No. 1, 2010

figure 1. Diagnosis: Acute Pericarditis

There� is� diffuse� ST-segment� elevation� that� is� concave

upwards,�with�J�point�elevation.�There�is�also�PR�depression

in�the�inferior�leads�and�PR�elevation�in�aVR.�This�represents

Stage�1�of�4�stages�of�ECG�changes�in�acute�pericarditis.

figure 2. Diagnosis: Pulmonary Embolism

When�the�pulmonary�artery�is�severely�obstructed�by�large

pulmonary� emboli,� there� may� be� right� heart� dysfunction.

This� ECG� demonstrates� the� rare� but� classic� signs� of� right

ventricular�strain:�deep�S�wave�in�lead�I,�deep�Q�wave�in�III,

inverted�T�wave� in� III�and� incomplete� right�bundle�branch

block�with�ST-T�changes�in�V1-V3.�However,� it�should�be

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-excita-

tion syndrome

Wolff-Parkinson-White� (WPW)� syndrome� is� a� congenital

abnormality�that�involves�the�pre-excitation�of�the�ventricles

through� an� atrioventricular� (AV)� accessory�pathway� called

the� Bundle� of� Kent.� Since� the� electric� impulse� travels

through� the� accessory� pathway� and� bypasses� the�AV�node

delay,� the� classic� findings�of�WPW�as� shown� in� this�ECG

are:�short�PR�interval�(<120�ms),�wide�QRS�complex�with

slurred�upstrokes�(delta�waves),�as�seen�here�in�leads�I,�aVL

and�the�anterior�precordial�leads.�

figure 4. Diagnosis: hyperkalemia

This� ECG� shows� signs� typical� of� hyperkalemia,� including

wide�QRS�complex,�tall�peaked�T�waves,�prolonged�QT�and

PR� intervals,� with� flattened� and� diminished� P� waves.

Hyperkalemia� increases� the�activity�of�potassium�channels

and�speeds�up�membrane�repolarization,�causing�tall�peaked

T� waves.� It� also� slows� impulse� conduction� and� prolongs

depolarization,�leading�to�small�P�waves�and�widened�QRS

complex.�

figure 5. Diagnosis: Atrial flutter with 2:1 AV Block

This�ECG�demonstrates�a�narrow�complex�tachycardia,�with

negative�sawtooth�complexes�in�inferior�leads�characteristic

of�typical�atrial�flutter.�By�mapping�the�P�waves�in�lead�V1,

it�can�be�shown�that�the�atrial�rate�is�300�beats�per�minute.

The�number�of�QRS�complexes�indicates�the�ventricular�rate

is� 150� beats� per�minute.�There� is� a� 2:1� conduction� block,

since� the�atrioventricular�node�cannot�conduct�at� the� same

rate�as�the�atrial�activity.

figure 6. Diagnosis: Bifascicular block and 2:1 AV Block

This�ECG�has�an�atrial�rate�of�75�beats�per�minute�and�a�ven-

tricular�rate�of�30�beats�per�minute.�Every�other�P�wave�is

followed�by�a�QRS�complex,�thus�there�is�a�2:1�atrioventric-

ular� block.� The� presence� of� right� bundle� branch� block

(RBBB)�is�indicated�by�rSR’�complex�and�inverted�T�wave

in�lead�V1�and�deep�S�wave�in�V6.�There�is�also�a�left�ante-

rior� fascicular�block�(LAFB),� identified�by� left�axis�devia-

tion,�with�small�q�and�big�R�waves�in�I,�and�small�r�with�big

S� waves� in� III.� The� combination� of� RBBB� and� LAFB� is

referred� to�as�bifascicular�block.�With�such�advanced�con-

duction� system� disease� and� a� slow� heart� rate,� this� patient

needs�a�pacemaker.

ACKNOWLEDGEMENTECGs�and�editing�are�courtesy�of�Dr.�Rajeev�Rao,�cardiolo-

gy� fellow� of� the� Division� of� Cardiology,� Department� of

Medicine,� Michael� G.� DeGroote� School� of� Medicine,

McMaster�University.

Author BiographyLucy Lu is a second-year medical student at the Michael G. DeGroote School of Medicine at McMaster University. Shepreviously studied life sciences at the University of Toronto.