CVS: Common Abnormalities With ECGs

Question 1

Where can supraventricular rhythms arise?

Answer 1

• Sinus node
• Atrium
• AV node

Question 2

Describe an ECG resulting from a supraventricular rhythm.

Answer 2

• Normal (narrow) PQR complex as the ventricles depolarise normally

Question 3

Describe an ECG resulting from a ventricular rhythm.

Answer 3

• Depolarisation takes longer hence a longer QRS complex

- Wide QRS complex

Question 4

What are the conditions for sinus brachycardia?

Answer 4

Sinus rhythmn with a rate of <60/min

Question 5

What are the conditions for sinus tachycardia?

Answer 5

Sinus rhythm with a rate >100/min

Question 6

Describe the appearance of an ECG with AF.

Answer 6

• No P waves, just a wavy baseline

- Irregular QRS complex as only some impulses are conducted to the ventricles

Question 7

What is heart block?

Answer 7

Delay/failure of conduction of impulses from the atria to the ventricles via the AV node and bundle of His

Question 8

What is first degree heart block?

Answer 8

When there is slow conductance in the AV node and His bundle.

Question 9

Describe the appearance of an ECG with first degree heart block.

Answer 9

• P wave normal
• PR interval prolonged (>5 small squares)
• QRS normal

Question 10

Describe the appearance of an ECG with type 1 second degree heart block.

Answer 10

• Progressive lengthening of PR interval

- Occasional dropping of QRS complex then the cycle begins again

Question 11

Describe the appearance of an ECG with type 2 second degree heart block.

Answer 11

• PR interval is normal

- Sudden dropping of QRS complex

Question 12

Describe the appearance of an ECG with third degree heart block.

Answer 12

• Wide QRS complex (due to ventricular escape rhythm)

- No relationship between P waves and QRS complexes

Question 13

Describe the appearance of an ECG with a ventricular ectopic beat.

Answer 13

Wide QRS complex that is completely different shape to the others.

This is because there is an ectopic focus in the ventricle muscle so the impulse isn’t spread via the fast purkinje system.

Question 14

Define ventricular tachycardia.

Answer 14

A run of three or more consecutive ventricular ectopic.

Question 15

Does a patient with VF have any CO?

Answer 15

Nope

Question 16

Which leads suggest ischaemia in the lateral view of the heart?

Answer 16

I
aVL
V5
V6

Question 17

Which leads suggest ischaemia in the inferior view of the heart?

Answer 17

II
III
aVF

Question 18

Which leads suggest ischaemia in the septal view of the heart?

Answer 18

V1

V2

Question 19

Which leads suggest ischaemia in the anterior view of the heart?

Answer 19

V3

V4

Question 20

Which muscle of the heart is most vulnerable due to coronary atherosclerosis?

Answer 20

The Sub endocardial muscle which is the furthest away from the blood supply.

Question 21

What does a ST segment depression/ T wave depression suggest?

Answer 21

Ischaemia

Question 22

What does a ST segment elevation and deepening Q waves suggest?

Answer 22

Complete occlusion (STEMI) resulting in an area of necrosis

Question 23

What is the criteria to deduce a pathological Q wave?

Answer 23

• > 1 small square in width
• > 2 small squares deep
• depth more than 1/4 of the height of the subsequent R wave

Question 24

In hyperkalemia, is the rest in membrane potential more or less negative?

Answer 24

Less

Question 25

In hypokalemia, is the rest in membrane potential more or less negative?

Answer 25

More

Question 26

Describe the ECG of a patient with hyperkalaemia.

Answer 26

Normal apart from an abnormally high T wave.

Question 27

Describe the ECG of a patient with hypokalaemia.

Answer 27

Normal apart from an abnormally low T wave.