Pacemakers

Question 1

Indications for a pacemaker?

Answer 1

• Symptomatic bradycardia
• Mobitz type 2
• Third degree heart block
• Heart failure
• Hypertrophic Obstructive Cardiomyopathy

Question 2

Features of a pacemaker?

Answer 2

• Pacemaker box (pulse generator).
• Pacing leads (carries the electrical signal)
• Computer which monitors electrical activity in the heart and responds accordingly.

Question 3

Contra-indications of a pacemaker?

Answer 3

• MRI scan, although most MRI scans are compatible with modern pacemakers
• Transcutaneous electrical nerve stimulation (TENS) machine
• Diathermy

Question 4

Why is it important to ask if the deceased has a pacemaker?

Answer 4

Because it will blow up in the crematorium

Question 5

What are the different types of pacemakers?

Answer 5

Single chamber
> Pacing lead in the right atrium if there is a problem with the SAN but not AV node.
> Pacing lead in the right ventricle, if there is an abnormality in the AV conduction and you want to contract the ventricles straight away.

Dual chamber
> Pacing leads both in the right atrium and the right ventricles, to synchronise the contraction of the atria and ventricles together.

Biventricular (triple chamber) pacemaker.
> Pacing leads found in the right atrium, right ventricle and left ventricle.
> This pacemaker is used in a patient with severe heart failure. This is because you want to synchronise the contraction of all the chambers to optimise heart function.
> These pacemakers are also called cardiac resynchronisation therapy (CRT) pacemakers.

Implantable cardiovertor defibrillator
> For patients with hypertrophic obstructive cardiomyopathy
> The defibrillator will send an electrical shock to bring back the heart into sinus rhythm.

Question 6

What ECG changes are associated with a single chamber pacemaker and dual chamber pacemaker?

Answer 6

Single
> If pacing lead is in the right atrium –> sharp spike before the p wave.

> If the pacing lead is in the right ventricle –> sharp spike before the QRS complex.

Dual
> Sharp spikes before the p wave and the QRS complex due to pacing leads being present in the right atrium and the right ventricle.