Cardiac Pacing

title: Cardiac pacing tags: #FFICM #cardiac notebook: ð-FFICM type: anki

[[cardiac]]

Indications for Temporary or Permenant Pacing

Symptomatic Bradycardia
Long QT
HCM
Congestive Cardiac Failure
Overdrive Pacing for SVT/VT/VF
Prophylactic post cardiac surgery (particularly valves) ¹

Flashcard	type:basic
In addition to the obvious use for a pacemaker (symptomatic bradycardia), what are the other indications for pacing patients?	Post Op Cardiac Surgery (Valves) CCF Long QT HCM Overdrive

Indications for Temporary Pacing

Sustained symptomatic bradycardia not responding to medical treatments
Malignant Ventricular Arrhythmias
2nd/3rd Degree Heart Block with CV compromise
Asystole ¹

Pacing Technicalities

Pacing leads are stiff
They are usually around 4-6 F in diameter
Place into a central vein in a 5-6 French sheath
Place into:
RIJ
Subclavian
Femoral
Manipulate under fluoroscopy
Aim for Apex of RV ¹

Flashcard	type:basic
What imaging do you use when placing a temporary pacemaker lead?	Fluoroscopy
Three big vessels you might place a temporary pacemaker lead into?	RIJ R Subclavian Femoral
How thick are temporary pacemaker leads?	~4-6 French
How thick is the sheath for a temporary pacemaker lead?	~5-6 French
Which part of the heart do you aim for with a temporary pacemaker lead?	~ Apex of RV

Risks include: - Perforation of RV - Pneumothorax - Arterial Puncture - AV Fista - Undersensing - Inappropriate Pacing and Pacemaker induced arrhythmias - Oversensing - Pacemaker inhibition and loss of CO - Failure to capture - Diaphragmatic Capture - Thrombus of central vein - Infection - Worry after 7 days in temporary leads ¹

Flashcard	type:basic
What physical damage can a pacemaker lead do, resulting in complications?	RV Perforation Pneumothorax AV Fistula Arterial Puncture
If a temporary pacemaker lead isn't fully working properly, what complications could you have?	Undersensing (too many pacing spikes) Oversensing (too few pacing spikes) Failure To Capture (no pacing spikes!) Diaphragmatic Capture (pacing the diaphragm!)
How long after temporary pacing wire has been inserted, should you start to worry about infection?	~ 1 Week

What to do with sudden failure to pace, keep working down list until acceptable option found:

Is pacemaker ON and connected to leads?
Is output set to maximum? (10V or 20mA)
Pick either DOO or VOO as mode. You don't want something being inhibited by intrinsic
Connect pacemaker direct to pacing lead (skip the connecting wire if there is one)
Get another pacemaker box/batteries
Start transcutaneous pacing
Use CPR and drugs if needed ¹

Flashcard	type:basic
Troubleshooting a pacemaker that has suddenly failed, what is your first step?	1. Is pacemaker ON and connected to leads?
Troubleshooting a pacemaker that has suddenly failed, what is your step after: 1. Is pacemaker ON and connected to leads?	2. Is output set to maximum? (10V or 20mA)
Troubleshooting a pacemaker that has suddenly failed, what is your step after: 1. Is pacemaker ON and connected to leads? 2. Is output set to maximum? (10V or 20mA)	3. Pick either DOO or VOO as mode. You don't want something being inhibited by intrinsic
Troubleshooting a pacemaker that has suddenly failed, what is your step after: 1. Is pacemaker ON and connected to leads? 2. Is output set to maximum? (10V or 20mA) 3. Pick either DOO or VOO as mode. You don't want something being inhibited by intrinsic	4. Connect pacemaker direct to pacing lead (skip the connecting wire if there is one)
Troubleshooting a pacemaker that has suddenly failed, what is your step after: 1. Is pacemaker ON and connected to leads? 2. Is output set to maximum? (10V or 20mA) 3. Pick either DOO or VOO as mode. You don't want something being inhibited by intrinsic 4. Connect pacemaker direct to pacing lead (skip the connecting wire if there is one)	5. Get another pacemaker box/batteries
Troubleshooting a pacemaker that has suddenly failed, what is your step after: 1. Is pacemaker ON and connected to leads? 2. Is output set to maximum? (10V or 20mA) 3. Pick either DOO or VOO as mode. You don't want something being inhibited by intrinsic 4. Connect pacemaker direct to pacing lead (skip the connecting wire if there is one) 5. Get another pacemaker box/batteries	6. Start transcutaneous pacing
Troubleshooting a pacemaker that has suddenly failed, what is your step after: 1. Is pacemaker ON and connected to leads? 2. Is output set to maximum? (10V or 20mA) 3. Pick either DOO or VOO as mode. You don't want something being inhibited by intrinsic 4. Connect pacemaker direct to pacing lead (skip the connecting wire if there is one) 5. Get another pacemaker box/batteries 6. Start transcutaneous pacing	7. Use CPR and drugs if needed
Troubleshooting a pacemaker that has suddenly failed, what are 7 bullet points to work through to get it to work?	1. Turn it On and Connect Wires 2. Maximum Output 3. Mode DOO/VOO 4. Plug directly in (skip connecting wires) 5. Change Pacemaker Box 6. Start Transcutaneous Pacing 7. Start CPR/Drugs

Systems can be:

Temporary
Permanent
Temporary-Permanent ¹

Initial Settings:

Set at least 10bpm faster than intrinsic, or 60 (pick whichever is faster)
Set pacing output at 5V
Set sensitivity at 1mA
Confirmation by pacing spike followed by QRS
Decrease output until capture is lost, then increase to lowest point it remains
Aim is less than 1 V
Set voltage at 3x the pacing threshold to give a safety margin ¹

Flashcard	type:basic
What should be the starting rate you set when using a temporary pacing system?	10bpm faster than intrinsic, or 60bpm, whichever is faster
How do you set up pacing output when using a temporary pacing system?	Start at 5V Decrease to loss of capture Increase to just regained capture Times that pacing threshold by 3 to give a safety margin

Intrinsic Noise Affecting Pacemaker:

Patient muscles
Lead Fracture ¹

Extrinsic Noise Affecting Pacemaker:

Electromagnetic interference (inc surgical diathermy) ¹

Problem with pacemaker noise is it might think it is VF/VT and shock them! ¹

Flashcard	type:basic
Where are the three places that temporary cardiac pacing leads can be attached?	Transvenous (into heart) Epicardial (surface of heart) Transcutanous (patches on skin)

Haemodynamics

Loss of AV synchrony (like AF) can result in decrease of CO by up to 25%
AV synchrony is also lost in VVI/VVIR pacing
This loss of haemodynamics doesn't seem to translate to any change in mortality though ¹

Flashcard	type:basic
How big a loss in cardiac output does loss of AV synchrony result in?	Loss of 25%
What is the most common reason a patient loses AV synchrony in cardiac cycle?	AF

Pacemaker Codes

Position (Letter) I : Chamber Paced

O = None
A = Atrium
V = Ventricle
D = Dual ¹

Position (Letter) II : Chamber Sensed

O = None
A = Atrium
V = Ventricle
D = Dual ¹

Posistion (Letter) III : How Pacemaker Responds To Sensed Event

O = None - Pay no attention to sensed events
T = Triggered - Pace when you sense an intrinsic event
I = Inhibited - Don't pace when you sense intrinsive event
D = Dual - Can pace or stop pace, in dual chambers if you sense atrial you'll inhibit the atrial pace but trigger the ventricular. If you sense ventricular you inhibit both ¹

Flashcard	type:basic
When looking at a pacemaker code, what does the first letter mean?	Which chamber is being paced
When looking at a pacemaker code, what does the second letter mean?	Which chamber is being sensed
When looking at a pacemaker code, what does the third letter mean?	What does the pacemaker do when it senses?
What letters could you see in the first or second letters in a pacemaker code, and what would they mean?	A (Atria) V (Ventricles) O (None) D (Dual)
What letters could you see in the third letters in a pacemaker code, and what would they mean?	O (Ignore Sensed Events) T (Pacing Triggered by sensed events) I (Pacing Inhibited by sensed events) D (Pacing either inhibited or triggered by sensed events, depending on atrial or ventricular)

Position (Letter) IV : Permanent Pacing Only - Rate Modulation

O = Rate Modulation Off
R = Rate Modulation On - Put HR up when you need it up ¹

Position (Letter) V : Multisite Pacing Or Not

O = Off
A = Atrium
V = Ventricles
D = Atrium and ventricles ¹

Source for these questions [[mcqs-and-sbas-in-intensive-care-medicine-oxford-higher-special-training]]

Flashcard	type:basic
When looking at a pacemaker, what does the fourth letter stand for?	Rate Modulation
When looking at a pacemaker, what does the fifth letter stand for?	Multisite pacing
How can you tell if a pacemaker is a dual chamber (atrial and ventricular) one?	Look at the fifth letter, for D

Examples

AOO / VOO
Paces that chamber only
No sensing
No synchronising w intrinsic
Just Paces
VVI
Ventricular Demand (Single Chamber)
Increases ventricular rate on top of intrinsic.
Most common for life threatening bradyarrhythmias
AAI
Atrial Demand (Single Chamber)
Increases atrial rate, on top of intrinsic
DDD
Paced + Sensed Both Chambers.
So it's added on top of own activity.
It will not be triggered by tachydysrhtmias.
DDI
Paced both chambers.
Senses both chambers.
Not triggered by Atrial Avents. So won't be messed up by AF. ¹

Flashcard	type:basic
When investigating a pacemaker, what does AAI mean it does?	Paces and senses atria. Inhibited by intrinsic activity. It will add it's pacing in addition to what the atria is doing already.
When investigating a pacemaker, what does AOO mean it does?	Paces atria. Does not sense anything. Payes no attention to what heart is trying to do itself, will just keep pacing.
When investigating a pacemaker, what does VOO mean it does?	Paces ventricles. Does not sense anything. Payes no attention to what heart is trying to do itself, will just keep pacing.
When investigating a pacemaker, what does VVI mean it does?	Paces ventricles. Senses what ventricles are trying to do. Inhibited by intrinsic activity. It adds it's pacing on top of what ventricles are doing anyway.
When investigating a pacemaker, what does DDD mean it does?	Paces atria and ventricles. Senses atria and ventricles. Does a bit of inhibiting pacing and triggering pacing, depending on what activity it senses.
When investigating a pacemaker, what does DDI mean it does?	Paces atria and ventricles. Senses atria and ventricles. Will be inhibited by any intrinsic activity, so won't go nuts if AF is going on.

Overdrive Pacing

If you set pacemaker at a faster rate than the intrinsic, you can suppress ventricular and supraventricular rhythms
For VT: Set the pacemaker at 120% of the VT beat for ~10 beats
For slow VT: You might need a lot longer than 10 beats here, Slow VT can be v stable.

Flashcard	type:basic
What is the aim of "overdrive pacing" in dysrhythmias?	To suppress and terminate any tachydysrhythmia
Practically, how do you set up a pacemaker to "overdrive pace"?	Set the pacemaker to go around 20% faster than the intrinsic activity, for around 10 beats.

ICDs

These can recognise and terminate VF and VT

Either through overdrive pacing or shocks

Get placed transvenously

Recognise VF when rates are > 200, and shock

Recognsise fast VT when 170 to 200, will try overdrive and then shock if no success

Recognise slow VT when 150 to 170 and try same as for fast VT, but with more overdrive ¹

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