Cardiac Implantable Electronic Devices (CIEDs)

 

The basics:

Terms

·     CIED = umbrella

·     PPM = pacemaker

·     ICD = defibrillator

·     AICD = term is no longer used

Components

·     Box – subcut vs subpectoral

·     Electrodes to sense electrical activity

·     Leads to deliver pacing impulse

Indications

·     Conduction system doesn’t work -> PPM

·     Tachyarrhythmia -> ICD

·     Severe heart failure + very wide QRS -> CRT-P

·     Severe heart failure + very wide QRS + tachyarrhythmia -> CRT-D

·     N.B. all modern ICDs can pace

 

Coding:

 

Pacemakers:

1 Pacing

2 Sensing

3 Response to sensing

4 Rate modulation

5 Multi-site pacing

O

O

O

O

O

A

A

I

R

A

V

V

T

 

V

D

D

D

 

D

O = none

A= atrium

V = ventricle

I = inhibited

T = triggered

D = both things (with A-V delay)

R = rate modulation: accelerometry, thoracic impedance, QT interval, etc

 

Defibrillators:

1 Shock

2 Anti-tachycardia

(i.e. overdrive pacing)

3 Detection

4 Anti-bradycardia

(i.e. normal pacing)

O

O

E

O

A

A

H

A

V

V

 

V

D

D

 

D

O, A, V, D = as above

E = electrical

H = haemodynamics

 

Interference:

Electrical:

 -Diathermy

·     PPM: interprets as native electrical activity -> inappropriate flatline

·     ICD: interprets as tachyarrhythmia -> inappropriate shock

 -Effect of magnet

·     PPM: asynchronous 80-100bpm with fixed A-V delay

·     ICD: shock and anti-tachy disabled, anti-brady (≈PPM) no effect

o  Inappropriate inhibition of pacing can occur

·     PPM-ICD: shock disabled, anti-tachy disabled, PPM no effect

o  Inappropriate inhibition of pacing can occur

·     Bi-V PPM: asynchronous, changes A-V delay (?)

Mechanical:

 -CVC insertion

·     Jiggle ICD lead -> shock

·     i.e. must apply a magnet

 -Physical oscillation

·     Inappropriate triggering of rate response function

·     e.g. sternal sawing, pulling a specimen out of a laparoscopy port site

MRI:

 -Problems

·     Mechanical injury

·     Thermal injury

·     Inappropriate pacing or no pacing or shock

·     Imaging artifact

 -Risk factors

·     Older device <2010

·     Strong magnet >1.5T

·     Thoracic imaging

 

Assessment:

What is it?

·     History

·     Medical record

·     CXR appearance and code

Why is it there?

·     Bradyarrhythmia / syncope / pacemaker-dependence (PPM)

·     Tachyarrhythmia / arrest (ICD)

·     Heart failure (Bi-V PPM)

Magnet possible?

·     Morbid obesity

·     Lateral or prone

·     Sterile field (can put in sterile USS probe cover)

Effect of magnet?

In general:

·     PPM: asynchronous

·     ICD: disable shock and overdrive

·     PPM-ICD: disable shock and overdrive, no effect on pacing

Effect of interference?

In general:

·     PPM: inappropriate suppression

·     ICD: inappropriate shock

Likelihood of interference?

·     Supra-umbilical

·     Proximity <15cm

Consequence of interference?

·     PPM: pacemaker-dependence

·     ICD: frequency of shocks

 

Management:

Device

·     Nothing

o  If interference unlikely

o  If interference inconsequential

·     Magnet

o  Continuous vs intermittent vs back-up

o  Check that it works pre-op

o  If wanting shock, remove magnet

·     Reprogramming

o  Safest option

o  If magnet ineffective (i.e. every PPM-ICD)

o  If magnet impossible

o  Must apply defib pads if disabling ICD

Monitoring

·     Observation – especially if disabling ICD

·     ECG – especially if disabling ICD

·     SpO2 – ensure alarms for flatline

·     A-line – if concerned or if SpO2 unreliable

Diathermy

·     Prefer short bursts

·     Prefer bipolar

·     If monopolar, place pad far away

 

X ray appearance:

Single chamber

Dual chamber

CRT - biventricular

 

CRT – His bundle

CRT-D

ICD

 

 

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