Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
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.
|
