Pacemakers and ICDs

Question 1

Reasons for artificial pacemaker fitting

Answer 1

Sinus node dysfunctions
Type 2 or 3 heart block
Hypertrophic cardiomyopathy
Long QT syndrome
cardiac resynchronisation therapy patients following severe cardiac failure

Question 2

Types of pacemaker

Answer 2

Fixed rate or on demand
Single dual or biventricular

Question 3

3 ECG features of pacemakers

Answer 3

Pacemaker spikes
Long QRS over 0.12 seconds
Appropriate discordance of S and T waves.

Question 4

Pacemaker spikes meaning

Answer 4

Single spike before P wave = atrial pacing
Single spike before QRS = ventricular pacing
2 spikes either side of P wave = dual pacing
no spikes = pacing inhibited by pacemaker in an on demand type.

Question 5

Capture beat

Answer 5

An unpaced beat originating from nodes

Question 6

Fusion beat

Answer 6

Unpaced beat and pacing at teh same time. Shorter pacemaker site and narrow QRS.

Question 7

Capture

Answer 7

Refers to contraction caused by pacing

Question 8

ICDs

Answer 8

Internal cardiac defibrillator used for patients at risk of VF or VT arrythmias.
Continuous monitoring of heart rate and shocks delivered if shockable rhythm detected.
Inferior to collarbone with two leads in right atrium and ventricle.

Question 9

Anti-tachycardia pacing

Answer 9

Used in patients with VT to reduce shocks. ICD becomes pacemaker with rapid burst of pacing and then gradual slowing to allow normal sinus rhythm to be restored.

Question 10

Modified sgarbossa criteria

Answer 10

Used to identify ECG features present in known LBBB/paced patients experiencing a stemi.
- Positive QRS with ST elevation > 1mm
- negative QRS with ST depression > 1mm
- Excessive dis-concordance over 25%