L12 - ECG 2

Question 1

What constitutes a normal sinus rhythm?

Answer 1

Regular rhythm
Initiated at SA node
P waves upright (in lead II) and present
QRS less than or equal to 3 small boxes (0.12 secs)
PR intervals 3-5 small boxes (0.12-0.2seconds)
Every p wave followed by a QRS complex

Question 2

What is a common cause of heart block?

Answer 2

Acute mi/degenerative changes

Question 3

Define a first degree heart block as per ECG

Answer 3

Prolonged PR interval (>0.2 seconds)

Question 4

Describe the differences between mobitz type 1 and mobitz type 2 second degree heart block

Answer 4

Type 1. - successively longer PR intervals until loss of one QRS

Type 2 - PR intervals do not lengthen but sudden loss of QRS complex

Question 5

In 3rd degree (‘complete’ heart block), a ventricular ‘escape’ rhythm takes over because the ventricles are depolarising independently. Describe this rhythm on an ECG

Answer 5

Slow (30-40bpm), wide QRS complexes, no congruency between p and QRS because both are depolarising independently

Question 6

What is the range for a normal HR?

Answer 6

60-100bpm

Question 7

Describe a characteristic ECG of a bundle branch block

Answer 7

Wide QRS, p wave and PR interval normal

Question 8

What is a supraventricular rhythm?

Answer 8

Any rhythm which arises above the ventricles

Question 9

How can you easily distinguish between a supraventricular and ventricular rhythm?

Answer 9

Narrow or wide QRS complexes

Question 10

Describe an ECG of atrial fibrillation

Answer 10

No p waves, wavy baseline. Narrow QRS complexes with irregular R-R intervals
Heart rate and pulse irregular

Explanation - p waves are reaching AV node but not all are conducted because of AB refractory period

Question 11

What condition is described by random wide QRS complexes followed by normal rhythm?

Answer 11

Ventricular ectopic beats

Question 12

When do ventricular ectopic beats becomes ventricular tachycardia?

Answer 12

When there is a run of three or more consecutive ectopic

Question 13

What does a ventricular fibrillation look like?

Answer 13

Complete loss of organisation. Rapid, irregular rhythm that can lead to cardiac arrest

Question 14

In a blood test how would you distinguish between whether a patient has angina or has had an MI

Answer 14

Presence of cardiac troponins indicating muscle necrosis in MI

Question 15

Which kind of MI is

a) the full thickness of the myocardium involved
b) the sub endocardium affected only

Answer 15

a) STEMI

b) NSTEMI

Question 16

STEMIs are the result of a complete occlusion of coronary artery by a thrombus, ST elevation is the earliest sign, then Q wave gets deeper and T wave inverts. Which symptom of these three persists in patients post STEMI?

Answer 16

Deep Q wave

Question 17

What ECG changes are seen in an NSTEMI and severe ischaemia (unstable angina) (look the same - differentiated by blood test)

Answer 17

ST depression and T wave inversion

Question 18

In NSTEMI, the coronary vessel isn’t completely occluded so deep q waves don’t occur, what is the difference between stable and unstable angina?

Answer 18

Stable - ST depression seem during exercise but normal at rest

Question 19

Describe an ECG of someone who is hyperkalaemic

Answer 19

Resting membrane potential is less negative
Tall peaked T wave (earliest sign)
Flattened p wave/ absent p waves depending on how severe
Prolonged PR interval, wide QRS
‘Sine wave pattern’ in severe

Question 20

Describe a hypokalaemic ECG

Answer 20

Flat T wave
Low ST segment
High U wave (after t wave)

Question 21

explain how you would calculate HR from a regular and irregular ECG differently

Answer 21

Regular - 300/number of big boxes in R-R interval

Irregular - 30 big boxes, number of R waves x 10