Heart blocks and heart failure

Question 1

What is the electrocardiograph?

Answer 1

The machine which produces an ECG recording

Question 2

What are the standard limb leads used for an ECG?

Answer 2

Right arm, Left arm and left leg

Question 3

Where is lead 1?

Answer 3

Between the right and left arm?

Question 4

Where is lead 2?

Answer 4

Between the right arm and left leg?

Question 5

Where is lead 3?

Answer 5

Between the left arm and the left leg

Question 6

Which lead shows the biggest deflection?

Answer 6

Lead 2 as depolarisation occurs in this direction

Lead 1 = smallest

Question 7

How long is the PR interval?

Answer 7

0.12-0.2 seconds

Question 8

How long is the QRS complex?

Answer 8

0.08-0.1 seconds

Question 9

How long is the QT interval?

Answer 9

0.4-0.43 seconds

Question 10

How long is the ST interval on average?

Answer 10

0.32 seconds

Question 11

What is a high p wave amplitude a result of?

Answer 11

Atrial hypertrophy - more muscle mass = bigger depolarisation = bigger deflection

Question 12

What does a low T amplitude show?

Answer 12

Ventricular hypoxia - not enough oxygen present for ventricles to contract

Question 13

What is sinus arrhythmia?

Answer 13

Heart rate increases by 15% during inspiration - seen less in adults

Question 14

What are first degree heart blocks?

Answer 14

Interruption somewhere between the SA and AV nodes slowing down conduction between the two nodes
Longer PR interval

Question 15

What is mobitz type 1?

Answer 15

Progressive prelongation of the PR interval culminating in a non-conducted p wave
The PR interval is longest immediately before the dropped beat and shortest immediately after
P waves continue at the same rate

Question 16

How can you tell the difference between mobitz type 1 and mobitz type 2?

Answer 16

Mobitz 1 = PR intervals change

Mobitz 2 = PR intervals do not change

Question 17

What is mobitz 2?

Answer 17

Usually due to the failure of conduction at the level of the His purkinje system
More likely to be due to structural damage to the conducting system

Question 18

How is mobitz 2 all or nothing?

Answer 18

His -purkinje cells suddenly and unexpectedly fail to conduct a supra ventricular impulse

Question 19

What is a third degree heart block?

Answer 19

Complete absence of AV concution - none of the supraventricular impulses are conducted to the ventricles
The perfusing rhythm is maintained by a junctional or ventricular escape rhythm
Alternatively the patient may suffer ventricular standstill = syncope or sudden cardiac death
Typically the patient will have severe bradychardia with independent atrial and ventricular rates ie AV dissociation

Question 20

What is sick sinus syndrome?

Answer 20

Impaired SA node firing eg brady or tachycardia

Question 21

What is happening if the jugular vein is pulsing?

Answer 21

Atria are contracting against a closed tricuspid - sends a cannon wave in the jugular vein
The right atria and ventricle contract at the same time so a pressure wave is sent back up the jugular veins

Question 22

What can atrial fibrilation cause?

Answer 22

Rapid/irregular heart rates
Exercise intolerance
Angina
Shortness of breath
Oedema of the ankles

Question 23

How can atrial fibrilation be treated?

Answer 23

Flecainide
Beta blockers, especially sotalol
Amiodamine
Dronedarone (only for certain people)
Warfarin and other anticoagulants - stop clots forming if the blood is pooling as this could cause a pulmonary embolism

Question 24

What is a circus movement?

Answer 24

An electrical signal not completing the normal circuit but rather an alternative circuit looping back on itself rapidly

Question 25

How can refractory muscle become non-refractory?

Answer 25

Unidirectional block

Transient biderectional block

Question 26

What are the stages in re-entrant excitation?

Answer 26

1) The originating impulse will set up the re-entrant excitement amd the unidirectional conduction block prevents further transmission
2) System behaves as an independent pacemaker with a rate higher than the originating impulse
3) The wave of excitation can travel in the reverse direction
4) The block allows retrograde transmission