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189 Cards in this Set

  • Front
  • Back
Define the abbreviations:
P, A, R, V, I
P=native atrial depolarization
A=atrial paced event
R= native Ventricular depolarization
V=Ventricular paced event
I=Interval
define the abbreviations:
AV, AVI
AV= sequential pacing in atrium and ventricle
AVI= programmed AV pacing interval
define the abbreviations:
AR, ARP
AR= atrial paced event followed by intrinsic ventricular depolarization
ARP=atrial refractory period
define the abbreviations:
PV
PV= native atrial depolarization followed by a paced ventricular event, P-synchronous pacing
define the abbreviations:
AEI
AEI=interval from a ventricular sensed or paced event to an atrial paced event, the VA interval
define the abbreviations:
LRL, URL, MTR, MSR
LRL= lower rate limit
URL=upper rate limit
MTR= maximum tracking rate
MSR= maximum sensor rate
define the abbreviations:
PVARP, RRAVD
PVARP=postventricular atrial refractory period
RRAVD=rate-responsive atrioventricular delay
define the abbreviations:
VA, VRP
VA=ventriculoatrial interval: interval from a sensed or paced ventricular event to an atrial paced event
VRP=ventricular refractory period
Ohm's law formula
V= I x R
If voltage is turned up there is a (high/low) current drain.
HIGH
If the impedence is___ what is the problem?
<250 ohms...
500 Ohms
>1000 ohms
<250= insulation defect
500 normal pacing impedence
>1000 lead fracture
If you reduce voltage by half what does current do?
also cut in half
If you reduce impedence by half what does current do?
it is doubled
If the impedence increases, the current------
decreases
An insulation break (decreases/increases) impedence
decreases
A wire fracture (increases/decreases) impedence.
increases
If there is an insulation break, impedence can fall to ____ Ohms and the current will (increase/decrease) and do what to the battery?
fall to below 300 Ohms
current will increase
battery will drain
A wire fracture will cause raise impedence to _______
Current will be (low/high)
may exceed 3000 Ohms
current will be low, may be too low to be effective
A pacer is a pulse _________.
It delivers ________stimuli over wires with electrodes in contact with heart.
generator
electrical
What kind of battery does a pace have?
What is a pacer made out of?
lithium iodine
titanium
A pacer lead is bipolar...the cathode is located at_______and the anode is at _______
cathode at tip
anode 2nd electrode
In terms of the battery what is BOL, and EOL stand for?
BOL=beginning of life
EOL= end of life
At the BOL, the electrolyte barrier is (thin/thick) and the resistance or impedence is (low/high)? What about the EOL?
BOL= barrier thin, impedence low
EOL=barrier thick, resistance high
What decreases battery life?
(low/high) voltage
(short/long) pulse duration
high voltage
long pulse duration
What is Ah?
ampere-hour,battery life
How much Ah does a pacer generally hold?
0.8-2.5 Ah
What is the output voltage of a fresh cell?
when do you replace?
2.8 V
replace @ 2.2-2.4 volts
The cathode is the____pole and the anode is the ___ pole.
cathode=negative
anode=positive
What are the two functions of a pacer lead?
deliver electrical impulses from the pulse generator to the heart.
sense cardiac depolarization
Where are the two types of lead placement?
endocardial or transvenous
epicardial or myocardial
Where is a transvenous lead introduced?
Into a vein :)
Where is an epicardial lead placed and how is it placed?
to the outside of the heart introduced through the chest wall.
Under what circumstances would you use a epicardial lead over the more common transvenous lead?
When no venous access is available or post CABG. Requires thoracic surgery
What is the pulse duration?
amount of time the battery gives off current
What are the two types of fixation mechanisms for transvenous
passive=tines become lodged in the trabeculae (grappling hook)
active= the helix or screw extends into endocardial tissue, allows for lead positioning anywhere in heart's chamber
What are the three types of myocardial or epicardial fixation mechanisms?
epicardial stab-ins
myocardial screw-ins
suture on
Which electrode is in direct contact with the heart?
(cathode/anode)
cathode
c for contact, electricity Comes to or enters
Which electrode receives the electrical impulse after depolarization of cardiac tissue? (cathode/anode)
anode
A for away, current is flowing away from the heart
Where is the anode located with a unipolar pacing system?
At the pacemaker
What path does the current flow on to and from the cathode in a unipolar system?
To the heart via body tissue, returns to pacemaker through conductor lead
Unipolar leads have (smaller/larger) diameter lead bodies than bipolar.
smaller
Unipolar leads usually exhibit (smaller/larger) pacing artifacts on the surface ECG
larger
Bipolar leads see/sense (small/large) areas compared to unipolar.
small areas
Bipolar leads are (more/less) susceptible to oversensing noncardiac signals
less
Programming is from ___ to ___
Telemetry is from ___ to ___
programming is from controller to pacemaker
telemetry is from pacemaker to controller
How long does the average modern pacemaker last?
7-10 years
Indications for Pacemaker
Sinus node dysfunction
AV block
Bifasicular/trifasicular block
hypersensitive carotid sinus syndrome (CSS)
Vasovagal Syncope (VVS)
Pacing after cardiac transplantation
AV block associated with myocardial infarction
children and adolescents (?)
name the temporary pacemaker insertion sites
internal/external jugular vein
subclavian vein
brachial vein
femoral vein
name the permanent pacemaker insertion sites
subclavian
cephalic
axillary
NOT jugular NOT femoral
What types of blocks do we put pacemakers in for?
2nd degree type II and 3rd degree
The pacemaker pocket is (over/under) the pectoralis major muscle and (above/below) the clavicle
over the muscle
below the clavicle
Which part of the heart is mostly anterior, which is mostly posterior?
right or left
right is anterior
left is posterior
What is subclavian crush syndrome?
Subclavian crush syndrome is a well-described cause of pacemaker lead failure (fracture or insulation breaks) resulting from an entrapment of a lead or leads between the clavicle and the first rib
How can you prevent subclavian crush syndrome
A more lateral puncture, or by using the axillary vein or cephalic vein
What is Twiddlers syndrome?
Where the lead is tightly twisted upon itself with the development of tension
What causes twiddlers syndrome?
Elderly patients who unwittingly twirl the pacemaker.
Obese patients with loose pacemaker pocket
Excessively large pacemaker pocket
What are the consequences of Twiddlers syndrome?
lead fracture
insulation defect
disconnection of the lead with failure to pace
How is twiddlers syndrome diagnosed?
standard chest x-ray
What is diaphragmatic stimulation?
Stimulation of the diaphragm, through ventricular perforation, thin ventricular wall, phrenic nerve stimulation
What should you always consider when diaphragmatic stimulation is observed?
RV lead perforation
What are some causes of muscle stimulation?
insulation break
missing plastic plug
perforating lead tip
What is Pacemaker runaway?
Pacemaker induced ventricular tachycardia
What is a single-chamber system?
The pacing lead is implanted in the atrium or ventricle depending on the chamber to be paced or sensed
What are the advantages and disadvantages of single chamber pacing systems?
Adv- implantation of single lead
Dis-single ventricular lead does not provide AV synchrony, single atrial lead does not provide ventricular back-up if A-to-V conduction is lost.
What is a dual-chamber system?
One lead implanted in the atrium, one implanted in the ventricle.
If the endocardial stimulatino is coming from the right ventricle what does the ECG resemble?
LBBB
If the epicardial stiumlation is from the left ventricle what does the ECG resemble?
RBBB
If you electronically double a 2.8V battery what do you get?
5.4 Volts
What can create unintended sensing and why?
Pacer stimulus, b/c it dissipates over longer time than spike...creates after potentials
What is the pacing threshold?
minimum needed to capture, voltage plus pulse duration
What is the stimulation threshold?
The minimum electrical stimulus needed to consistently capture the heart outside of the heart's refractory period.
The pulse width must be long enough for depolarization to disperse to the surrounding tissue, decrease voltage and increase pulse duration until loss of capture
The pacing threshold is the shortest pulse duration that captures the heart while keeping the output voltage constant
What is the safety ratio concept for capture measured in? What is the safety margin?
Volts not pulse duration
2 volts, (100%)
What is the tripling pulse duration at fixed voltage?
adequate safety, but not past 0.2 ms, flat part of curve, pulse duration >/=0.3ms
What is the safety ratio for Chronic pacing thresholds with steroid eluding leads
<2.5 V at 0.5ms
What do newer pacers have for threshold determination
automatic, periodically by programmer
After patient safety, the second most important goal in programming is to_______
extend battery life
What is the best way to extend the service life of a battery?
lower voltage settings while maintaining adequate safety margins
List the factors that affect battery longevity (4)
lead impedance
amplitude and pulse width setting
percentage paced vs. intrinsic events
rate responsiveness modes programmed "on"
What are the 3 phases of lead maturation?
acute- where thresholds immediately following implantation are low
peaking-where thresholds rise and reach their highest point(1 wk-6-8 weeks)
chronic-thresholds assume stable reading, higher than implantation but lower than peak
What do steroid tips do for maturation process?
nearly eliminate the peaking phenomenon of the lead maturation process
What is sensing?
the ability of the pacemaker to see when a natural intrinsic depolarization is occuring(by measuring changes in electrical potential between anode and cathode)
What is an EGM and what are its two characteristics
Electrogram-recording of cardiac waveforms taken from within the heart, occurs when intrinsic depolarization passes directly under the electrodes.
signal amplitude
slew rate
What is slew rate?
the rate of change in signal amplitude per unit of time
Sensitivity...the greater the number, the ____ sensitive the device to intracardiac events
less
What is undersensing
the pacemaker does not see the intrinsic beat and therefore does not respond appropriately
What is the difference between automatic interval and escape interval?
automatic is based on programmed RRI
escape interval is time from sense of intrinsic to next programmed spike
Higher sensitivity means (less/more) millivolt?
less
What is oversensing?
an electrical signal other than the intended P or R wave is detected
Lower sensitivity means (less/more) millivolt?
more
What do sensing amplifiers filters do?
allow appropriate sensing of P and R waves and reject inappropriate signals
What are the most common unwanted signals
T waves
far field events (R waves sensed by atria)
Cross talk in dual chamber pacers(ventricular sensing of atria)
Skeletal myopotentials (pectoral muscle myopotential)
What 3 things is accurate sensing dependent on?
The electrophysiological properites of the myocardium
The characteristics of the electrode and its placement within the heart
The sensing amplifiers of the pacemaker
What are 3 factors that may affect sensing?
lead polarity (uni, bi)
lead integrity (break, fx)
EMI- electromagnetic interference
Why does unipolar sensing produce a large potential difference?
a cathode and anode that are farther apart than bipolar system
Why does Bipolar sensing produce smaller potential difference
short interelectrode distance, therefore electrical signals from outside the heart such as myopotentials are less likely to be sensed
Does an insulation break cause undersensing of oversensing?
Both, undersensing when inner and outer conductor coils are in continous contact
Oversensing when inner and outer conductor coils make intermittent contact
What do they mean by continous contact with inner and outer coils
Signals from intrinsic beats are reduced at the sense amplifier and amplitude no longer meets the programmed sensing value
What do they mean by intermittent contact with the inner and outer coils
Signals are incorrectly interpreted as P or R waves
Does a wire fracture cause undersensing or oversensing?
Both
undersensing-occurs when the cardiac signal is unable to get back to the pacemaker, intrinsic signals cannot cross the wire fracture
oversensing-occurs when the severed ends of the wire intermittently make contake, which creates potentials interpreted by the pacemaker as P or R waves
What is EMI?
Electromagnetic Interference-interference is caused by electromagnetic energy with a source that is outside the body
What type of fields may effect pacemakers?
radio-frequency waves
What Hz is associated with interference?
50-60 Hz are most frequently associated with pacemaker interference
What problems may result with EMI (3)
oversensing
transient mode change (noise reversion)
Reprogramming (power on reset or "POR")
Rates will (speed up/down) if EMI signals are sensed as P waves in dual-chamber system
up-accelerate (p waves are tracked)if dual chamber sees both P and R than rate will be increased (should only see R's)
Rates will be (high/low) if EMI sensed in single-chamber system, or on ventricular lead in dual-chamber system
Low or inhibited, single chamber sees more and thinks they are intrinsic so doesn't fire=lower rate
What is noise reversion
continuous refractory sensing will cause pacing at the lower or sensor driven rate
What is POR
power on reset or back up mode, may exhibit a mode and rate change which are often the same as ERI
What are some sources of EMI with new technology?
digital cell phones
electronic article surveillance
metal detector gates
What are sources of EMI within the hospital?
electrocautery
thransthoracic defibrillation
extracorporeal shock-wave lithotripsy
therapeutic radiation
RF ablation
TENS unit
MRI
What is the most common hospital source of EMI
electrocautery
What are the outcomes of EMI
oversensing-inhibition
undersensing (noise reversion)
power on reset
permanent loss of pacemaker output
What are some precautions to make with EMI
reprogram to VOO/DOO mode, or place a magnet over device
strategically place the grounding plate
limit electrocautery bursts to 1-second burst every 10 seconds
use bipolar electrocautery forceps
What are the outcomes of transthoracic defibrillation with PM
inappropriate reprogramming of the pulse generator
damage to pacemaker circuitry
What are some precautions to take with transthoracic defibrillation with PM's
position defib paddles apex-posterior and as far from the pacemaker leads as possible
Can a patient with a pacemaker have an MRI?
Contraindicated-outcomes extremely high pacing rate, reversion to asynchronous paicng
precaution-program pacemaker output low enough to create persistent non-capture, ODO or OVO mode
What does lithotripsy shock waves do to PM's
In dual chamber modes-inhibition of ventricular pacing
In rate adaptive PMs-high pacing rates, piezoelectric crystal damage
What precautions do you take with PMs and Lithotripsy
program pacemaker to VVI or VOO mode
Lithotriptor focal point should be greater than 6 inches from the pacemaker
carefully monitor heart function throughout procedure
What kind of radiation can may cause perm. damage?
Ionizing radiation like that of breast of lung CA therapy, can damage semi-conductor circuitry,
What are some outcomes of therapeutic radiation
pacemaker circuit damage
loss of output
runaway
may be permanent, requires replacement of pacemaker
What are some precautions to take with therapeutic radiation therapy?
keep cumulative radiation absorbed by the pacemaker to less than 500 rads, shielding may be required
Check PM after radiation sessions for changes in function
PM sensing circuits amlify, filter and either process or reject signals, what are the steps?
Input
band pass filter
absolute value
reversion circuit
level detector (sensitivity adjustment)
pacemaker logic
What is rate responsive pacing
AKA rate modulated
PM provide patient with the ability to vary heart rate when the sinus node cannot provide the appropriate rate
What is rate responsive pacing indicated for?
pts who are chrontropically incompetent (HR doesn't increase to meet demands)
patients in chronic atrial fibrillation with slow ventricular response
What is another name for chronic A-fib with slow ventricular response?
tachy-brady syndrome
seen with sick sinus syndrome
SV reserves can account for increases in CO of up to_____
HR reserves can nearly _____ total CO in response to metabolic demands
50%
triple
What type of sensors exist for rate response
activity sensors, detect physical movement and increase rate accordingly
Minute ventilation sensors that measure the change in respiratory rate and tidal volume via transthoracic impedence readings
What do activity sensors use to detect movement
piezoelectric crystal, detects mechanical motion and transalates signal into electrical signal
What is minute ventilation
volume of air introduced into the lungs per unit of time, composed of tidal volume and respiratory rate per minute
What is the NBG code categories
I-chamber paced
II- chamber sensed
III-response to sensing
IV-programmable fx/rate modulation
V-antitachy function
For paced and sensed what does V, A, D, O, S stand for?
For response to sensing what does T, I, D, O stand for?
V-ventricular
A-atrium
D-dual
O-none
S-single
T-triggered
I-inhibited
D-dual
O-none
For programmable functions what does P, M, C, R stand for?
For Anti-tachy functions what does P, S stand for?
P-simple programmable
M-mulit-programmable
C-communitcating
R-rate modulating

P-pace
S-shock
What does VVI mean?
ventricular paced, sensed and response to sensing=inhibition
What is the difference between triggered and inhibited?
triggered-if it sees something it paces
inhibited-if it sees something, pacing is inhibited
What is the difference between single and dual chamber triggered modes?
in single-if intrinsic event is sensed then pace given immediately after
in dual if intrinsic event sensed, sensed atria event, triggers AV delay
What does AAI mean
Atria paced, atria sensed, response to sensing-inhibited
What does VVT mean?
Ventricular paced, ventricular sensed, Response to sensing-triggered
What does VAT mean?
Ventricular paced, atrial paced, Response to sensing (atrial) triggered
What would DDD mean?
dual V and A pacing, sensing and dual triggers and inhibits
What is demand pacing?
VVI, pace and sence in ventricle, pace inhibited if intrinsic sensed
What is Lower rate interval
defines the lowest rate the pacemaker will pace, automatic interval
What is the refractory period?
interval initiated by a paced or sensed event, designed to prevent inhibition by cardiac or non-cardiac events, RP started by a paced, non-refractory or refractory sensed event
What is the concept of pacemaker refractory period
pacemaker sees but is unresponsive, designed to avoid restarting the LRI in the event of oversensing (T wave)
Pacemaker ventricular refractory period avoids the sensing of (5)
its own stimulus
the paced QRS
the T wave
(excessive)afterpotential
the combination of T wave and afterpotential
What does Ellenbogen say to set RP at to minimize chance of sensing T wave
400 ms
What is the blanking period
the first portion of the refractory period, pacemaker is blind to any activity, designed to prevent oversensing pacing stimulus
What is difference between refractory period and blanking period?
blanking doesn't see anything
refractory period sees but doesn't act
What is the typical blanking period in a single chamber mode
100 msec
What is upper sensor rate interval
defines the shortest interval (highest rate) the pacemaker can pace as dictated by the sensor (AAIR and VVIR) modes
What is rate modulated pacing
sensor function-refers to change of rate in response to a signal, can happen w/ or w/o depolarization
What type of signals are there?
T wave interval
QTI
Vibration or acceleration d/t physical activity
central venous temp
central venous O2 sat
impedance signals for measuring min ventilation
What is VOO mode
Venricular paced, no sensing, no response to sensing, just set pacing at set interval
What is the aka for VOO mode?
ventricular asynchronous
What mode does the PM revert to when a magnet is placed over it?
VOO mode
An intrinsic beat will do what to the lower rate interval
reset it
What is the VVT mode?
ventricular paced and sensed, Triggered response
rarely used, vent stimulus released immediately upon sensing, ensures stimulation when sensed, requires 3 timing intervals-LRI, VRP, URL
What is AAIR
atrial paced, sensed, inhibited sensing, rate modulated. Atrial based pacing allows the normal A-V activation sequence to occur
What is AAI pacemaker used for
Only for BRADY!!
AV block is not a problem, pacer RP should be set at >400ms, prevents far field sensing, lower cost, preservation of normal vent depolarization
What is hysteresis
allows the rate to fall below the programmed lower rate following an intrinsic beat
Without hysteresis the automatic interval_____the escape interval
With hysteresis the escape interval is ________ than the automatic interval
equals
longer than
What are the advantages of hysteresis
the spontaneous AV synchrony can be maintained as long as possible
Prevents symptomatic retrograde VA conduction
allowing a lower rate increases the battery longevity.
What is noise reversion?
continous refractory sensing will cause paicng at the lower or sensor driven rate
What are the benefits of dual chamber pacing
provides AV synchrony
lower incidence of atrial fibrillation
lower risk of systemic embolism and stroke
lower incidence of new CHF
lower mortality and higher survival rates
According to a study what hemodynamic factors benefit with dual chamber pacing
improved CI during low level exercise
increase in LV filling
30% increase in resting CO
decrease in PWP
Decreased incidence of mitral and tricuspid valve regurgitation
What are the four faces of dual chamber pacing
AP/VP
AP/VS
AS/VP
AS/VS
What is AP/VP?
patient with sinus node dysfx and AV block
What is AP/VS?
ventricular output is inhibited by a sensed ventricular event
What is AS/VP?
atrial rate is driving the ventricular rate-also called atrial tracking, adequate sinus node function with AV block
What is AS/VS?
adequate sinus node function and intact AV conduction, little to no increase in sinus rate with activity and/or AV block that occurs at increased rates, at appropriate rates, it is best to try and utilize the patients intrinsic rhythm when possible
What are the dual chamber timing parameters
lower rate
AV and VA intervals
Upper rate intervals
Refractory periods
Blanking periods
The lower rate interval is almost always based on (atria/vent) events
ventricular
Which travels faster paced or intrinsic?
Intrinsic b/c travels norm conduction pathway
Which should be less PAV or SAV
SAV<PAV
What does PAV and SAV stand for?
PAV is paced atria-ventricle interval
SAV is sensed atria-ventricle interval
The Lowest rate interval= what?
AEI + AVI
The AEI is from what to what
the patients Q wave to the paced P wave
What is TARP
total atrial refractory period, AVI + PVARP
(post ventricular refractory period)
What does VA interval equal?
the LRI-AVI
What is the atrial escape interval? (VA interval)
the interval initiated by a paced or sensed ventricular event to the next atrial event
What does the VRP do
intended to prevent self-inhibition such as sensing of T waves
What does the PVARP do?
intended primarily to prevent sensing of retrograde P waves
From what to what is the PVARP?
paced V to end of TARP
interval after a ventricular paced or sensed event during which the atrial channel is refractory
What are the functions of the PVARP
avoids the inappropriate atrial sensing of ventricular events
avoids sensing of retrograde conducted P waves
What is the PVAB
post ventricular atrial blanking period
initiated by ventricular pace or sensed event
nominally set at 220 msec
avoid the atrial lead sensing the far field ventricular ouput pulse or R wave
What is atrial stimulus crosstalk?
programmable (nominally at 28 msec)
relatively short blanking period b/c it is important not to miss ventricular events that occur early in AV interval
When atrium sees stimulus in ventricle and responds to it and vice versa
Ventricular blanking does not occur coincident with an atrial sensed event b/c?
the intrinsic P wave is relatively small and will not be far-field sensed by the ventricular lead
What should you be cautious with a too long blanking period?
undersensing of vent events
cause the PM to pace in the ventricle after the AV interval expires
could occur before ventricle has repolarized and initiate R on T
What is the upper activity sensor rate?
in rate responsive modes, the upper activity rate provides the limit for sensor-indicated pacing
What is the upper tracking rate?
the maximum rate the ventricle can be pace in response to sensed atrial events.