What is a pacemaker or Defibrillator

EP: The Shocking Truth!
Nursing Grand Rounds
June 15, 2011
Kris Martin, RN
Julie MacDonald, RN
Wyman Ground
in between the OLD ICU and
Radiation Oncology
What do we do?
Pacemaker and ICD implants
Electrophysiology Studies
Cardioversions (Electrical and Chemical)
Yearly Defibrillator testing
Ablations- Atrial flutter and SVT, AVNRT
Tilt-Table Testing
Pacemaker/ICD Clinic
Why an EP study?
Diagnoses abnormal heart rhythms and/or induces
cardiac arrhythmia's in order to:
• Determine the source of arrhythmia symptoms
• evaluate the effectiveness of certain medications in
controlling the heart rhythm disorder
• predict the risk of a future cardiac event, such as Sudden
Cardiac Death
• assess the need for an implantable device (ICD or
pacemaker) or treatment procedure (ablation)
copyright Heart Rhythm Society 2004
An Overview of the Procedure
• Pt receives conscious sedation and local
• Femoral VEIN is accessed-one or both sides.
• EP catheters are guided under fluoroscopy to the
right atrium and ventricle via the IVC.
• Electrodes at catheter tip collect data from various
points in the heart (electrical mapping).
• Various arrhythmia's can then be induced or
ablated, or the decision to implant
a pacemaker or ICD can be made.
We Maintain a Sterile environment, same as the OR
• Radio frequency energy is delivered through EP
catheters to burn a small section of the
• This prevents the arrhythmia from continuing or
• At Mount Auburn, we do SVT and Atrial flutter
ablations (Afib and VT ablations are not done
• EP studies and ablations are typically done as
outpatient procedures.
These are EP catheters seen on X-ray
• Transesophageal echocardiogram
• Ultrasound probe passed into esophagus-posterior
view of heart.
• Diagnoses thrombus, valve disease, septal defects
?source of embolus, bacteremia, or CVA/TIA.
• Pre-cardioversion to rule out existing thrombus.
• Patients get conscious sedation and generally need
to remain NPO for 4 hours after.
• Synchronized shock to terminate Afib or
• Pts receive MAC (monitored anesthesia
care-propofol) by anesthesiologist
• Chemical Cardioversions are when
medications are given like Ibutilide or
Flecainide and EKG is monitored for
conversion and arrhythmia.
Defibrillator Testing
• DFTs: defibrillator threshold testing.
• Usually done on ICD implant and yearly, or
if there is a potential device/lead issue.
• Frequently outpatient basis.
• Patient receives MAC (propofol).
• The ICD programer is used to induce VF
and looks for the device to deliver
a shock.
Pacemakers with leads
Pre-op Pacemaker/ICD implant
• Pt must be NPO after midnight
• No applesauce with meds or
OJ for low blood sugar!
• AM meds are okay with a small sip of water
• Meds to hold:
heparin, multivitamins, oral hypoglycemics,
• Check blood sugar if diabetic
• **LEFT sided IV**
Post-OP Care of Pacemaker/ ICD
• Watch site for S+S infection
pt will have prophylactic antibiotic
• Watch site for hematoma or bleeding
• Moderate amount of bleeding on DSD okay
• Bedrest usually for 12 hours post op
• Pain: Manual manipulation during implant
Percocet or Tylenol
Post Op Care
• Keep arm in sling overnight, affected arm stays lower
than shoulder height, no extended reaching
this helps prevent dislodgment of leads!
• Next day chest X-ray to confirm lead placement, and
device interrogation.
• Pt will have a Green/purple folder in chart to take
home. Please make sure to give them to patient on
• Call MD regarding procedure site, orders, function
of pacemaker.
• Thin wires with
flexible silicone
• Connect the
pacemaker generator
to the myocardium
• Sensing of heart
activity and discharge
of electrical impulse.
• Leads are screwed into
• 6-8 weeks for lead to
mature: scar tissue forms
around the lead and
anchors it.
• Extended reaching or
lifting during this time may
dislodge the lead requiring
Atrial lead
Pacemaker leads as seen on Xray(Dual chamber system)
Ventricular leads
Pacemakers and defibrillators are a complicated
business and that is why we have specialists.
As a nurse you can not figure out what a
pacemaker or ICD is doing by just looking
at the monitor.
There are a few things that you should know that
will help you decide what to do.
What is a pacemaker or
• Pacemaker is sensing and monitoring patients
own heart rate and delivers an impulse in either
the atrium or ventricle in the absence of a sensed
• Defibrillator is sensing and monitoring the
patients own heart rate for a fast rate usually set
188bpm to deliver a shock to convert to NSR. Can
also pace if heart rate is slow usually 40 bpm.
What do you need to know?
• How many leads does the pacemaker have?
1 lead only sees what is happening in its chamber
so a VVI pacemaker only knows what is
happening in ventricle.
2 leads sees what is happening in both chambers
the atrium and ventricle. Mode DDD/ DDI
• What is the lower rate set at?
If it is VVI @ 60 it will not pace if heart rate is
greater than 60bpm.
A Dual chamber pacemaker or DDD will pace
in Atrium at lower rate and then that sets up a timing
cycle for the Ventricle to either pace or inhibit.
In a DDD pacemaker you can see all different types of
pacing on EGM strips:
A sensed V sensed =
A paced V sensed =
A sensed V paced =
A paced V paced =
NSR/ AFIB, pacemaker is inbitited
Sinus bradycardia
Heart blocks / CHB/2:1 block
Heart block/Sinus arrest/asystole
Where will you find all this information?
You will find it in Meditech under Cardiology
Reports tab.
If there is no report then they have not been seen
at Mount Auburn Hospital Pacemaker Clinic.
Ask the patient/family if they have an ID card for their
pacemaker. Which will identify the manufacturer.
Call pacemaker clinic @ 5622 to evaluate the device.
Pacemaker Report
Pacemaker Report
Clinic Tel: 617/499-5628
Date of Pacemaker check: 03/14/11
Pacemaker Type: Medtronic Sensia
Implanted: 09/10/09
Pacemaker programmed rate: 70bpm
Mode: DDDR
Response with magnet: Asynchronous pacing 3 at 100bpm then 85bpm
Presenting Rhythm: AV Paced
Underlying Rhythm: HB with PVC
Pacemaker Dependent: N
Arrhythmia Recorded on Diagnostics: None
Battery Life Stable: Y
Impedance: A= 410 ohms RV= 531 ohms
Sensing: P-wave= 2.8 mv R-wave= 15.6 mv
LOC: A= 0.75 @ 0.4 ms RV= 0.75 @ 0.4 ms
Comments: In-house s/p fall. Appropriate sensing and capture testing. No
arrhythmia's recorded. Unable to promote intrinsic rhythm with AVD
at max, no changes made. Reprogramming for testing only. Follow
up in six months.
When would you apply a magnet to a pacemaker?
During electrocautery use in OR or GI Unit.
In a pacemaker a magnet causes the pacemaker to
Asynchronously pace at a set rate usually 85bpm-100bpm
What does this mean?
It means that the pacemaker can no longer see what the
patients heart is doing and is going to pace at the magnet rate.
If the patient is pacemaker dependent or has a HR below
85-100 then you need to apply a magnet. If a magnet is not
applied it could result in long pauses or asystole.
What if the patient has a Higher HR?
If a patient has their own HR then you would not apply
a magnet since asynchronous pacing could cause a
pacing spike to come in on a T-wave resulting in VT!
Remember when you place the magnet on a pacemaker
it can no longer see what the patient’s own heart is doing
A magnet should be available to place over device if
inhibition of pacing occurs resulting in pauses.
When do you call pacemaker clinic?
This device is over sensing and thinks it
sees ventricular activity and inhibits
What you might see on monitor
Normal function
Non Sensing of R wave
Non Capture
What do you need to know about an ICD?
•You need to know if it is a single (VVI) or dual
chamber(DDD) device and the lower rate.
• You need to know what the Zones are set at. VT zone or VF
• The magnet response will always be: Inhibits therapies, no
effect on pacemaker.
• If they are pacemaker dependent,they will need to be
reprogrammed for surgery to an Asynchronous
What do you need to know about a ICD?
• That it can overdrive pace a patient out of a
fast HR if it falls into the VT zone.
• That it is not always able to distinguish
between AFIB and VT especially if it is a
single lead device. A VVI device doesn’t
know what the atrium is doing.
• You can put a magnet over ICD to disable
the therapies and prevent or stop
inappropriate shocks.
ICD Report
ICD Report
Clinic Tel: 617/499-5628
Date of ICD check: 05/05/11
ICD Type: Boston Scientific Cognis
Implanted: 01/19/11
VT Zone: 185
VFIB: 220
ICD programmed rate: 60bpm
Mode: DDD
Response with magnet: Inhibits therapies, no effect on pacemaker
Presenting Rhythm: Unknown
Underlying Rhythm:
Pacemaker Dependent:
Arrhythmias Recorded on Diagnostics: none
Battery Life Stable: Y
Impedance: A= 439 ohms RV= 402 ohms LV= 949 ohms
Sensing: P-wave= mv R-wave= 7.0 mv LV-wave= 19.3 mv
LOC: A= @ ms RV= @ ms LV= @ ms
Comments: Latitude transmission, BiV pacing 92% of the time. Follow up in
This is what a magnet looks like some are blue
You can find them on all the code carts throughout
the hospital, in the OR and GI units.
When would you place a magnet over an ICD?
If a patient is getting inappropriate shocks.
During cautery in OR or GI unit.
CMO status until device can be reprogrammed.
A Doctors Order is need to apply a Magnet and
disable a device.
ICD Patients that are Pacemaker Dependent
• If they are pacemaker dependent,they will need to be
reprogrammed for surgery to an Asynchronous mode.
Remember that a Magnet only Inhibits therapies, has
no effect on Pacemaker in an ICD Patient.
How do you know if they are pacemaker dependent?
•Look at the report in Meditech.
you will need to call Pacemaker clinic 5622 to arrange
for someone to come and evaluate device and reprogram
if necessary.
In OR, GI unit when cautery is being used the ICD
should be disabled by a magnet.
Electrocautery can cause noise on the lead,
an ICD would interpret it as fast heart rate and deliver
an inappropriate shock.
The patient should always be on a monitor when
the magnet is in place.
The benefit of this is that if a VT/ VF episode
occurs you can remove the magnet and the device
will deliver a shock. If the device was programmed
OFF then would need to externally shock
the patient.
This is an example of noise
on an ICD lead from
The device thinks this is VF
and would deliver a shock if
a magnet was not applied.
You can always call clinic, 5622 and
we will help you figure it out!
If a patient has been made CMO you may place a
magnet over device until it can be reprogrammed.
A note must be in the chart from attending physician
that it has been discussed with patient and or family.
An order must be written to turn off ICD, before it can
be done. If you are applying a magnet an order should
be written.
This has no bearing on pacemaker portion of ICD and
we do NOT turn off pacemakers in CMO patients.
When would you apply a magnet to an ICD?
•If a patient was receiving shocks that you/MD
determine to be inappropriate you may apply a
magnet to stop the therapies/shocks.
•An example of this would be a patient who is in
rapid AFIB with ventricular rate in 190bpm and
has a single chamber device with a VT zone set for
188bpm. The ventricular lead only knows that the
rate is above 188bpm and that it is programmed to
give a shock.
Another example of when to place a magnet is
the patient is telling you they are getting Shocked
and this is the rhythm on monitor/EKG.
This is NSR and if the patient is getting shocks
from ICD, then you need to disable it with a magnet
The lead is most likely broken and over sensing
the device will continue to give shocks until it is
What if the device is not giving a shock and you see VT
on monitor?
The device will only do what it has been programmed to do
If a VT Zone is set at 188bpm and a patient is in a [email protected]
180bpm the device is never going to give a shock.
You would need to externally shock the patient.
The pads should be placed to avoid damaging the ICD.
What if your patient tells you his device is BEEPING
or VIBRATING in their Chest?
They are NOT crazy! The devices are set up to alert patients
of a problem.
You should notify the pacemaker clinic or cardiologist on
call. They can call in a company representative to interrogate
and find the problem.
The beeping and or vibrating will continue every 6-10hours
until device is reprogrammed.
Why is Pacemaker/ ICD follow-up important?
We often find new onset AFIB. Device can date and time
the event, amount and duration of episodes and give atrial
and ventricular rates.
We evaluate Histograms to tell us if the heart rate has been
fast or if it has been stuck at the lower rate. Medications are
often adjusted or Rate Response added.
Ventricular Long term Histogram
Rate (bpm)
% of Beats
We find broken leads or batteries that need replacement.
Non capture or
broken lead on
We find non-sustained episodes of VT in pacemaker
patients that otherwise would go undetected. This could
be causing them dizziness or syncope.
New onset Afib is common to find also.
In an ICD we can find episodes that received ATP or a
shock. After reviewing with the cardiologist, their
meds may be adjusted to prevent further therapies.
In an ICD we can find episodes of AF getting inappropriate
therapies. Medications would be evaluated and adjusted.
This is another example
of inappropriate shock for
Sinus Tachycardia
and the patient should
have medications adjusted
to prevent their sinus rate
from going this high.
The EP Staff
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