052 ECG and Heart Disease

Question 1

What are the different lead names in the 12 chest leads?

Answer 1

Chest leads V1-V6, Standard limb leads I, II, III, Augmented limb leads VR, VL, VF.

Question 2

On the chest leads, what is the pattern that occurs from V1 to V6?

Answer 2

As you move across V1 to V6, the R wave will become more and more positive, peaking at V4. At V6 there are no negative deflections.

Question 3

Describe the standard bipolar limb leads

Answer 3

Bipolar PD vectors:
Lead I goes from right arm to left arm
Lead II goes from right arm to left ankle
Lead III goes from left arm to right ankle

Question 4

Describe the augmented limb leads

Answer 4

Unipolar leads that measure current referenced to combination of other leads VF, VR, VL

Question 5

What are the degrees of directions for the different leads in relation to the axis?

Answer 5

Lead I 0 degrees 
Lead II 60 degrees
Lead III 120 degrees
VR -150 degrees 
VF  90 degrees
VL  -30 degrees

Question 6

What does higher amplitude indicate on the ECG?

Answer 6

More muscle to conduct electrical movement e.g. hypertrophy

Question 7

What does irregular T waves suggest?

Answer 7

High potassium levels causing irregular repolarization

Question 8

What is the direction of electrical impulse in the heart starting from the SA node?

Answer 8

SAN -> VAN -> Bundle of His -> Perkinje fibres

Question 9

What do PQRST signify?

Answer 9

P - atrial depolarization.
QRS - ventricular depolarization with Q being the first –ve deflection, R being first +ve deflection, and S being second –ve deflection.
T wave- repolarization of the ventricles.

Question 10

What determines the PR interval?

Answer 10

Conduction through the AV node

Question 11

What should be the PR time interval?

Answer 11

120-200ms

Question 12

Why would the PR be longer than normal?

Answer 12

If the AV node becomes scarred, it will take longer to conduct electricity through at that time.

Question 13

What determines the QRS complex interval?

Answer 13

His purkinje networks ensure rapid and synchronised ventricular depolarization that causes a short duration and large magnitude of QRS complex.

Question 14

What would there be a broad QRS complex?

Answer 14

If there are branch blocks within the fibers or abnorman ventricular activation

Question 15

How can you determine a right bundle branch block from a left bundle branch block?

Answer 15

Right bundle branch block results in irregular negative deflections. Left bundle branch blocks results in irregular positive deflections and cause the complex to be more negative.

Question 16

Which leads would have most impact during an anterior infarction?

Answer 16

V2, V3, V4

Question 17

Which leads will have most impact during lateral infarction?

Answer 17

I, V5, V6, AVL

Question 18

Which leads will have most impact during inferior infarction?

Answer 18

AVF, II, III

Question 19

How do you calculate rate of heartbeat?

Answer 19

300 / (no. of big boxes between peaks)

Question 20

What is the difference between a sinus rhythm, tachycardia, and bradycardia?

Answer 20

Sinus rhythm is regular PQRS complex
Tachycardia occurs when heart rate >100 bpm
Bradycardia occurs when heart rate <60bpm

Question 21

What are two different causes of bradycardia?

Answer 21

Bradycardia can be caused by

(1) Failure of SAN impulse generation
(2) Failure of impulse propagation

Question 22

How would you identify failure of SAN impulse generation?

Answer 22

When P wave is not present

Question 23

How would you identify failure of impulse propagation?

Answer 23

When there is a P wave but the QRS complex that follows is either prolonged (first degree) or is getting progressively longer (second degree), or does not stimulate a QRS complex at all and QRS is completely randomly timed (third degree).

Question 24

If tachycardia is caused supraventricular, what will you notice on the QRS complex?

Answer 24

Narrow complex <120msec caused by sinus tachycardia or supraventricular tachycardia

Question 25

If tachycardia is caused ventricularly, what will you notice on the QRS complex?

Answer 25

Broad complex >120msec caused by branch blocks or ventricular tachycardia.

Question 26

What is the ECG difference between atrial flutter and atrial fibrillation?

Answer 26

Atrial flutters shows saw tooth characteristics

Atrial fibrillation are “irregularly irregular”

Question 27

Which leads would be more positive/ negative during right axis deviation?

Answer 27

Leads (II) III, AV will be positive

Leads I, AVL will be negative

Question 28

Which leads would be more positive during left axis deviation?

Answer 28

Leads AVL, I, (AVR) will be more positive.
Leads II, III, AVF will be more negative.
If AVR is half half, then it means that it is deviated -90 degrees.

Question 29

Where are the chest leads placed?

Answer 29

V1 - 4th intercostal space right parasternally
V2 - 4th intercostal space left parasternally
V3 - Midway between V2 and V4
V4 - 5th intercostal space at midclavicular line
V5 - Anterior axillarly line at 5th intercostal space
V6 - Mid axillarly line at 5th intercostal space.

Question 30

How long should the QRS complex be?

Answer 30

< 120ms

Question 31

When would the leads show positive deflection?

Answer 31

When electrical activity is being conducted within 90 degrees of the lead direction.