Cardiac arrhythmias

Question 1

Where does each heart beat originate from?

Answer 1

SA node.

Question 2

What is the average beat from the SA node?

Answer 2

70 beats a minute.

Question 3

When will you see bradycardia (slowing of HR)?

Answer 3

Sleep.

Question 4

When will you see tachycardia (fast HR)?

Answer 4

1. Emotion.
2. Exercise.
3. Fever.
4. Other stimuli.

Question 5

When does the heart rate accelerate?

Answer 5

Inspiration - impulses in the vagi from the stretch receptors in the lungs inhibit the cardio-inhibitory area in the medulla oblongata. There is a decrease in tonic vagal discharge (that keeps the HR slow) so the HR rises.

Question 6

When does the heart rate decelerate?

Answer 6

Expiration.

Question 7

What is sinus arrhythmia due to?

Answer 7

Normal phenomenon - fluctuations in parasympathetic output to the heart.

Question 8

What happens in sick sinus syndrome?

Answer 8

Disease process that affects the SA node -> marked bradycardia -> dizziness and syncope.

Question 9

What is complete (third-degree) heart block?

Answer 9

Interruption to conduction from the atria to the ventricles.

Question 10

What happens in a complete heart block?

Answer 10

The ventricles beat at a low rate independent of the atria.

Question 11

What can cause complete heart block?

Answer 11

1. Disease in AV node - AV nodal block.
2. Disease in the conducting system below the node - infranodal block.

Question 12

in AV nodal block what tissue becomes the pacemaker?

Answer 12

Remaining nodal tissue - will roughly beat 45bpm.

Question 13

In infranodal block what tissue becomes the pacemaker?

Answer 13

Ventricular pacemaker (located peripherally) - 35bpm on average.

Question 14

What else can occur in patients with infranodal blocks?

Answer 14

Periods of asystole lasting >1 minute. This can result in cerebral ischaemia which can cause dizziness and fainting (stokes-adams ysndrome).

Question 15

What is incomplete heart block?

Answer 15

Conduction between atria and ventricles is slowed but not completely interrupted.

Question 16

What will you see on the ECG in first degree heart block?

Answer 16

PR interval is abnormally long - all the atrial impulses reach the ventricles.

Question 17

What will you see on the ECG in second degree heart block?

Answer 17

Not all atrial impulses are conducted to the ventricles. So a ventricular beat may follow every second or third atrial beat (2:1 block, 3:1 block).

Question 18

What is the wenckebach phenomenon?

Answer 18

Repeated sequences of beats with the PR interval lengthening progressively until a ventricular beat is dropped. The PR interval of the cardiac cycle that follows the dropped beat is usually normal or only slightly prolonged.

Question 19

What is a bundle branch block?

Answer 19

When one branch of the bundle of His is interuppted. Right or left bundle branch block.

Question 20

What occurs in a bundle branch block?

Answer 20

Excitation normally goes down the bundle on the intact side and then goes back through the muscle to activate the ventricle on the blocked side.

Question 21

What will you see on the ECG in a bundle branch block?

Answer 21

1. Prolonged QRS complex and deformed.
2. normal ventricular rate.

Question 22

What is a fascicular block?

Answer 22

Block in the anterior or posterior fascicle of the left bundle branch.

Question 23

What will you see in a left anterior fascicular block on an ECG?

Answer 23

Abnormal left axis deviation.

Question 24

What will you see in a left posterior fascicular block on an ECG?

Answer 24

Abnormal right axis deviation.

Question 25

What happens when His-purkinje fibres may discharge spontaneously?

Answer 25

There is increased automaticity of the heart and an ectopic beat can occur (beat that occurs before the expected next normal beat).

Question 26

What are the type of ectopic beats?

Answer 26

1. Atrial.
2. Nodal.
3. Ventricular - extrasystole or premature.

Question 27

What happens if ectopics fire repeatedly at a rate higher than the SA node?

Answer 27

Produces a rapid regular tachycardia - atrial, ventricular, or nodal paroxysmal tachycardia or atrial flutter.

Question 28

What is a circus movement?

Answer 28

Where there is a block on one side of the conducting system. So when impulses spread in both directions, one side is blocked. The other side continues around and when it reaches the blocked area, the impulse on the other side is in its refractory stage. The a impulse then continues going around in a circular position.

Question 29

What happens in a bundle of Kent?

Answer 29

There is an extra bundle of conducting tissue that connects the atria to the ventricles. This will allow for a re-entrant pathway to occur.

Question 30

What happens with atrial extrasystoles?

Answer 30

Another area in the atria will stimulate the AV node prematurely, hence the ventricles are conducted prematurely.

Question 31

What will you see on the ECG with atrial extrasystoles?

Answer 31

1. Abnormal P waves.
2. Normal QRS complex.

Question 32

What is atrial tachycardia?

Answer 32

When an atrial focus discharges regularly or there is reentrant activity. You will get atrial rates of up to 220/min.

Question 33

What is the atrial rate in atrial flutter?

Answer 33

200-350/min.

Question 34

What happens in atrial flutter?

Answer 34

Large counterclockwise circus movement in the right atrium.

Question 35

What will you see with atrial flutter on the ECG?

Answer 35

Sawtooth pattern of flutter waves.

Question 36

Why will you see sawtooth appearance