1. The Electrical Management of Cardiac Rhythm Disorders Bradycardia Device Course
The Electrical Management of Cardiac Rhythm Disorders, Bradycardia, Slide Presentation 06 Implant Technique
Implant Technique

2. Pacemaker Components

3. Leads
Epicardial
Endocardial

4. Goals of Cardiac Pacing
The electrical management of bradyarrhythmias requires
Ability to deliver enough energy to consistently depolarize the heart (capture)
Ability to correctly sense intrinsic cardiac activity
These functions are affected by many factors
Settings of output parameters (pulse amplitude, pulse width)
Sensitivity parameter settings
Impedance
Electrical concepts

5. Capture
The capture threshold is defined as the minimum amount of electrical energy required to consistently depolarize the myocardium
When a pacemaker output causes a depolarization, that is also called “capture”
The capture threshold is also called the pacing threshold or the stimulation threshold
The capture threshold is not constant
It can change over time (disease, medications, age)
It can even change over the course of the day!

6. What Affects the Capture Threshold?
Activity level
Posture
Time of day
Comorbidity
Heart failure
Meals
Drugs
Disease progression

7. Capture Threshold Values
Atrial
Ventricular
Acute Threshold
< 1.5 V
< 1.0 V
Chronic Threshold
< 2.5 V
Threshold values at implant should be low; expect chronic thresholds to increase
These are suggested values and may not be possible for all patients
Capture threshold values at implant should be low, usually not more than 1.5 V in the atrium and 1.0 V in the ventricle. The ideal chronic thresholds are below 2.5 V in both chambers. Keep in mind that such values are ideal and may not be possible for all patients.

8. Sensing
Sensing refers to how well the pacemaker is able to “listen to” or perceive intrinsic cardiac events
Important things to consider when talking about sensing
Surface ECG
Intracardiac electrogram (EGM)
Sensing threshold
Sense amplifier
Sensitivity setting and sensitivity safety margin
Unipolar/bipolar configurations
Electromagnet interference

9. Surface ECG/Intracardiac EGM
Surface ECG: graphic depiction of heart’s electrical signals recorded from electrodes on the body’s surface
Intracardiac EGM: graphic depiction of the heart’s electrical signals recorded by electrodes from inside the heart (pacing lead)

10. Sensitivity Safety Margin
Sensing thresholds are not constant and vary with many factors
The sensitivity safety margin allows reliable sensing even with fluctuations in the sensing threshold
Using this formula, the safety margin should be at least 2 at implant
Safety margin =
Sensing Threshold
Sensitivity Setting
Like capture thresholds, sensing thresholds can fluctuate with time and other factors, so a safety margin is required.
The safety margin should be calculated using this formula and should be 2 or greater. For instance, if a patient’s sensing threshold is 2 mV then the sensitivity setting should be 1 mV. Likewise, if the patient’s sensing threshold is 4 mV, the sensitivity setting should be 8 mV. This is a 2:1 ratio.
(Remember, increasing the mV setting decreases sensitivity.)

11. Electromagnetic Interference (EMI)
EMI is defined as electrical signals of nonphysiologic origin
May interfere with pacemaker (temporarily or permanently)
Common sources of EMI
Cardioversion/defibrillation
Electrocautery
MRIs
Extracorporeal shock wave lithotripsy (ESWL)
Therapeutic radiation
Radiofrequency ablation

12. What About Cardioversion/Defibrillation?
May permanently damage the pulse generator
Can temporarily inhibit or reprogram the pacemaker
Backup or noise reversion mode
Myocardial thermal damage secondary to shock which may result in ventricular fibrillation, myocardial infarction, or both
Guidelines
Evaluate potential device interactions
Place paddles 4 to 6 inches away from implanted pacemaker
Orient paddles in anterior/posterior position, if possible
This is a complicated subject that can only be addressed briefly. Cardioversion or defibrillation can cause a number of undesirable effects in a pacemaker patient. First, the shock energy can reprogram the pacemaker, might damage the pacemaker permanently, and thermal damage secondary to the shock traveling via the lead into the heart can cause VF, MI, or both.
The pacemaker may revert to a backup mode, sometimes called a “noise reversion mode.” These vary by manufacturers and devices but should be described in the device manual or known by the manufacturer’s technical services hot line or representative. It is important to rule out possible noise reversion mode when unexpected pacemaker behavior is observed. In most cases, noise reversion mode remains in force until the device is reprogrammed. The reprogramming step is simple.
Guidelines for pacemaker patients under consideration for cardioversion and defibrillation include how the paddles are placed (4 to 6 inches away from the implanted pacemaker) and oriented (AP, if possible). Careful consideration to potential device interactions should be weighed.

13. What About Electrocautery?
May reprogram or permanently damage the pacemaker
May inhibit the pacemaker
May cause the device to go into backup or noise reversion mode
Myocardial thermal damage secondary to the transmission of the electrical energy may result in VF, MI, or both
Guidelines
Contraindicated

14. What About MRI?
The magnet in the MRI device can cause asynchronous pacing (pacing without sensing)
Guidelines
Generally contraindicated
Magna-Safe Study

15. What About Lithotripsy?
The vibrations in extracorporeal shock wave lithotripsy can damage the pacemaker (especially pacemakers with sensors, i.e. rate-adaptive units)
Guidelines
Program to VVI or VOO mode
Keep focal point of lithotripter at least 6 inches away from the implanted pacemaker
Monitor the heart throughout the procedure

16. What About Therapeutic Radiation?
Damage depends on dose
Damage is cumulative; monitor device throughout course of radiation therapy
Transistors may fail
Pacemakers may fail but mode of failure cannot be predicted
Guidelines
Therapeutic ionizing radiation is contraindicated
If therapeutic radiation is used, pacemaker should be shielded or moved to a less vulnerable location
Note that there can be a difference between diagnostic radiation treatments and therapeutic radiation treatments. Some pacemakers utilize complimentary metal oxide semiconductors or CMOS technology. A CMOS-type pacemaker can be affected by therapeutic radiation but will not be affected by diagnostic radiation. To find out more, contact the technical services group of the manufacturer.

17. What About Radiofrequency Ablation?
RF ablation can temporarily or permanently reprogram the pulse generator
Guidelines
Interrogate the pacemaker following the procedure to verify proper function
If necessary, reprogram
RF ablation is unlikely to cause permanent damage to the device.

18. Myopotentials
Myopotentials are muscle noises that are sensed by the pacemaker
Can inhibit pacing
The pacemaker senses the myopotential and inhibits the output, thinking the heart has beat on its own!
Can interfere with sensing
Can cause inappropriate pacing
The pacemaker senses myopotential noise and inappropriately “thinks” it is atrial activity; it then tries to pace the ventricle to keep up or track that atrial activity

19. More EMI Sources Arc welding Automobile alternators Cell phones
Phone antenna should not overlap area of implanted pacemaker
Talk on other side from implanted device
Do not carry an activated cell phone near the implanted pacemaker
May cause inappropriate inhibition, asynchronous pacing, backup mode, inappropriate rate adaptation, and mode switching
Cellular Tested only from St. Jude Medical
There are other sources of EMI but cell phones continue to be of major interest. After all, how many pacemaker patients are arc welders? But just about everyone uses cell phones.
A cell phone may indeed interfere with a pacemaker. The results of that interference can include inapporpriate inhibition of the device, asynchronous pacing (no sensing), backup mode, and inappropriate behavior in terms of rate adaptation and mode switching.
General guidelines for all pacemaker patients: do not hold the cell phone on the same side of the body as the implanted device and do not carry a cell phone that’s ON near the pacemaker implant site.
St. Jude Medical is the world’s only pacemaker company to receive FDA approval to label its devices “Cellular Tested.” Since the Trilogy® pacemakers, all St. Jude Medical devices incorporate a protective filter which has been shown to help prevent unwanted signals from directly entering the pacemaker circuitry.

20. EMI in the Medical Environment
Electrocoagulation from electrocautery
Defibrillation
Electroconvulsive therapy
Diathermy
MRI
Stimulators (e.g. transcutaneous nerve)
Dental equipment
Diagnostic ultrasound
Low-frequency acupuncture
Lithotripsy

21. EMI in the Industrial Environment
Arc welding
Power lines
Transformers
Radio and TV transmitters
Static charge
Large metal frames in magnetic fields
Induction furnaces and heaters
Electrical switches

22. EMI in the Public Environment
CB radio
Radiofrequency transmissions
Telecommunications antennas
Airport metal detectors
Anti-theft detectors in stores
These may not be marked!
Digital cell phones
Anti-theft detectors include detectors at store exits. In many stores, it is clear where these are located (if you are looking for them). However, pacemaker patients should know that some stores may conceal these detectors. These pose more of a risk to the pacemaker patient in that the patient may stand or linger near a source of EMI without knowing it.

23. Effects of EMI Pacemaker protection
Hardware backup circuits (to protect against loss of memory or software errors)
Shields
Effects
EMI inhibition: pulse-to-pulse interval extends to the point that the pacemaker does not pace as often as it should.
Noise reversion: change in mode (typically to asynchronous pacing at the programmed rate) which may require reprogramming.
EMI tracking: acceleration of pacing as the pacemaker tries to track electromagnetic signals (“thinking” they are atrial signals)
First, pacemakers do have protection against EMI. After all, we can’t eliminate EMI—it’s everywhere. Pacemakers have shields and also backup circuitry.
There are three main effects of EMI. EMI may inhibit the device, it may cause a mode change (backup or noise reversion pacing), or it may accelerate the device. It is difficult to predict how a particular exposure to EMI will cause the device to function.

24. NASPE / BPEG (NBG) Pacemaker Code
Pacemaker Overview
NASPE / BPEG (NBG) Pacemaker Code

25. NAPSE/BPEG Generic (NBG) Code
Position I II
III IV V
Category
Chamber(s)
Paced
Chamber(s)
Sensed
Response
to Sensing
Rate modulation
Multisite Pacing
Letters
Used
O-None
A-Atrium
V-Ventricle
D-Dual
(A+V)
O-None
A-Atrium
V-Ventricle
D-Dual
(A+V)
O-None
T-Triggered
I-Inhibited
D-Dual
(T+I)
O-None
R-Rate modulation
O-None
A-Atrium
V-Ventricle
D-Dual
(A+V)
Manufacturer’s
Designation
Only
S- Single
(A or V)
S- Single
(A or V)

26. Magnet Use
Pacemakers
Pace Asynchronously (VOO or DOO) at the given battery rate (Temporarily)
Device will revert back to exactly the same parameters it was programmed to once the magnet is removed
ICD
Will disable ICD Shock Therapy (Temporarily)
Does not affect pacing
Device will revert back to exactly the same parameters it was programmed to once the magnet is removed.
Magnet must be placed over the device in order for temporary changes to occur.

27. A Systematic Approach to Diagnosing Rhythm Strips
Measure Base Rate
Measure AV/PV Interval
Verify Atrial capture
Verify Atrial sensing
Verify Ventricular capture
Verify Ventricular sensing
Verify Underlying rhythm
Document

28. Dual Chamber ECG Analysis
What is the Analysis?
Base Rate 60 ppm
MTR 120 ppm
AVD 200 ms
PVARP 250 ms
ECG # 1

29. Dual Chamber ECG Analysis
Base Rate 60 ppm
MTR 120 ppm
AVD 200 ms
PVARP 250 ms
What is the analysis?
ECG # 2

30. Dual Chamber ECG Analysis
What is the analysis
Base Rate 60 ppm
MTR 120 ppm
AV 200 ms
PV 200 ms
PVARP 250 ms
ECG # 3

31. Dual Chamber ECG Analysis
What is the analysis?
Base Rate 60 ppm
MTR 120 ppm
AV 200 ms
PV 200 ms
PVARP 250 ms
ECG # 4

32. ECG Tracing Results!!!
#1- Normal ECG –Dual chamber pacing and Atrial pacing w/ Ventricular (intrinsic) sensing.
#2- Loss of atrial capture.
#3- Normal ECG
#4-No ventricular sensing and loss of ventricular capture.

33. ECG #5 Appropriate atrial sensing Appropriate ventricular sensing
No paced events, so capture cannot be evaluated

34. Answer Slide #5 Normal Sinus Rhythm
Can not determine any pacemaker function
Pacers are usually set to pace above 50 or 60 bpm
Single Chamber ICD- Pace above 40bpm
Pacemakers only work when?
Native heart rate goes below the base rate
An intrinsic beat does not occur before the set Paced and Sensed AV Delays.
Set at an Asynchronous Mode (VOO or DOO)

35. Thank you for your time!!!