Electrocardiogram and Arrhythmias

Question 1

What waves are present on the normal ECG?

Answer 1

P wave
QRS complex
T wave

Question 2

What does the P wave represent?

Answer 2

Atrial depolarisation

Question 3

What does the QRS complex represent?

Answer 3

Ventricular depolarisation

Question 4

What does the T wave represent?

Answer 4

Ventricular repolarisation

Question 5

What does the PR interval represent?

Answer 5

Atrial to ventricular conduction

Question 6

What is a normal PR interval?

Answer 6

120-200ms

Question 7

What is the normal QRS length?

Answer 7

<120ms

Question 8

What is the normal heart rate?

Answer 8

60-100

• bradycardic <60
• tachycardic >100

Question 9

What is the cardiac cycle?

Answer 9

Systole + Diastole

Filling + contraction

Question 10

Describe the electrical activity of the heart

Answer 10

Pacemaker SA node - down atria - AV node - bundle of His - purkinje fibres

Question 11

Describe the mechanical activity of the heart

Answer 11

Relaxed chambers - atrial systole - isovolumic ventricular contraction - ventricular ejection - isovolumic ventricular relaxation - diastole

Question 12

What is the EDV?

Answer 12

End-diastolic volume

-maximum amount of blood in ventricles

Question 13

What is the ESV?

Answer 13

End-systolic volume

-minimum amount of blood in ventricles

Question 14

What are the ECG changes in 1st degree heart block?

Answer 14

P-waves present
P-waves followed by QRS
Prolonged PR interval (reg)

Question 15

What are the ECG changes in 2nd degree heart block? (Mobitz 1, Wenckebach)

Answer 15

P-waves present
P-waves not always followed by QRS
PR interval gradually lengthens until P wave dropped

Question 16

What are the ECG changes in 2nd degree heart block? (Mobitz 2)

Answer 16

P-waves present
P-waves not always followed by QRS
PR interval constant, P wave not always conducted

Question 17

What are the ECG changes in 3rd degree heart block?

Answer 17

P-waves present (unless AF)

No relation between P and R waves

Question 18

What are indications for pacemaker implantation?

Answer 18

High degree heart block
Distal heart block
Presence of symptoms

Question 19

Describe the ECG features of atrial fibrillation

Answer 19

Irregularly irregular rhythm
QRS <120ms
No P-waves
Chaotic ECG baseline

Question 20

Describe the ECG features of atrial flutter

Answer 20

Regular rhythm
QRS <120ms
No P-waves
Presence of flutter waves
-300bpm
-2:1

Question 21

Describe the ECG features of re-entrant tachycardia

Answer 21

P-waves often hidden in QRS
Pseudo R-waves (V1)
Pseudo S-waves (II, III, aVF)

Question 22

Describe the ECG features of ventricular tachycardia

Answer 22

Regular rhythm
QRS >120ms
P-waves may be present, no relationship w/ QRS

Question 23

Describe the ECG features of ventricular fibrillation

Answer 23

Irregular rhythm
QRS >120ms
P-waves absent

Question 24

Describe the ECG features of left ventricular hypertrophy

Answer 24

R-wave (V6) >25mm

Sum of S-wave (V1) and R-wave (V6) >35mm

Question 25

Describe the ECG features of right ventricular hypertrophy

Answer 25

Dominant R-wave (V1) T-wave inversion (V1-V4) Deep S wave (V6, RAD)

Question 26

Describe the ECG changes in LBBB

Answer 26

``` L-axis deviation Lead I +ve Lead II neutral/neg Lead III -ve WILLIAM ```

Question 27

Describe the ECG changes in RBBB

Answer 27

``` R-axis deviation Lead I -ve Lead II neutral/pos Lead III +ve MARROW ```

Question 28

Describe the initial ECG features of STEMI

Answer 28

Hyperacute T-waves | ST elevation <1hr

Question 29

How does the ECG of a STEMI patient develop?

Answer 29

Development of pathological Q wave Loss of R wave ST elevation reduces Inversion of T wave (late)

Question 30

What ECG changes of a STEMI persist?

Answer 30

Abnormal Q waves | Reduced R waves