pacemakers

Question 1

what are the two ways to correct symptomatic bradycardia?

Answer 1

atropine and or pacemaker

Question 2

when are temporary pacemakers used?

Answer 2

primary in emergency circumstances when the need for cardiac pacing is brief or self limited.

immediate correction of symp brady during severe sinus node dysfunction or advanced AV block

prophylactic intervention prior to procedures requiring a general anesthetic in patients who have underlying bifasciular block

tachyarrythmias that can’t be suppressed with drug therapies and the temporary pacer would be used to overdrive or break the rhythm

part of diagnostic procedures such as electrophysiology studies to evaluate the conduction system and the potential for arrythmias

Question 3

what are the two types of temporary pacing?

Answer 3

transvenous and epicardial pacing and transcutaneous pacing

Question 4

what is transvenous pacing? can u move around?

Answer 4

a temp pacing catheter placed thru either the femoral, brachial, jugular, or subclavian veins to stimulate the endocardial surface of the right ventricle. no bedrest cause it can move it

Question 5

what is epicardial pacing?

Answer 5

epicardial wires are temporarily sutured onto the epicardial surface of the RA and/or RV during cardiac surgery. the wires can exit through the chest wall and a re taped to the chest wall for quick access.

Question 6

what is trancutaneous pacing?

Answer 6

external pacing pads located on the anterior or posterior chest wall for emergency thranathoracic pacing with the use of the pacing mode on the LifePak defibrillator

Question 7

what is the most common form of temporary cardiac pacing?

Answer 7

ventricular demand pacing

Question 8

demand pacing utilizes what?

Answer 8

a ventricular lead which sense and pass and when the lead senses the patients QRS the pacing stimulus is inhibited and in the absence of pt QRS it will deliver a stimulus

Question 9

what does the pacing stimulus generate on an ECG

Answer 9

an electrical artifact referred to as a pacing spike

Question 10

what is pacemaker syndrome?

Answer 10

symp that patients may experienced when ventricularly paced for a long period of time. symp are fatigue, dizziness, syncope and pulmonary congestion. results from loss of AV synchrony and VV synchrony

Question 11

what does this loss of AV ad VV synchrony result in?

Answer 11

dec CO d/t loss of atrial contribution and ventricular filling

atrium contracting against a closed alive causing backflow of blood into pulmonary veins which can trigger atrial baroreceptors and cause hypotension

ventricular pacing is the only option for patients who have undergone AV node ablation for afib

Question 12

what is temporary atrial pacing? where is the lead? what node needs to function here? what is this useful for?

Answer 12

single lead placed in right atrium. once chambers are activated the electrical impulse is conducted through the normal conduction pathway to stimulate the ventricles. requires a healthy AV node and is useful for…

improving cardiac output by providing synchronized contraction of the atria and the ventricles and
-overdriving or suppressing supra ventricular tachydysthymias

Question 13

what is atrioventricular sequential pacing or dual chamber pacing?

Answer 13

pacing lead n both r atrium and r ventricle and requires an intact. requires orderly and sequential contraction of the atria and ventricles. AV synchrony provides the atrial contribution of atrial kick to ventricular filling and sig adds to CO. this atrial contibtribution is estimated to be 20-30% of the cardiac output. in its with marginal cardiac reserve acute MI pt (ex), the loss of AV synchrony may result in acute CHF and other decompensatory changes

Question 14

what is BiVentricular pacing or cardiac resynchronization therapy (CRT)?

Answer 14

lead in both ventricles. accomplished w a transenous lead placed in the RV (endocardial placement) and a second ventricular lead is threaded through the coronary sinus to be placed in a vein located on the epicardial surface of the left ventricle. the concurrent stimulation of the right and left ventricles results in a synchronous myocardial contraction reducing heart failure

Question 15

what is an ICD?

Answer 15

implantable cardioevrter defibrillator.

it is placed i pt with inc risk of sudden cardiac death due to lethal cardiac arrytmias. usually post MI and have congenital prolonged QT intervals and will keep arresting.

atrial and ventricular leads are located in the RA and RV. programmed to overdrive pace, cardiovert or debrillate VT or Vfib

Question 16

what are the components of pacemakers?

Answer 16

a temp consists of a transvenous bipolar catheter (lead) which is attached to an external pulse generator .

Question 17

what do bipolar pacemaker leads have?

Answer 17

2 electrodes in contact with the cardiac tissue. the distal or stimulating electrode is usually neg (cathode) one and the positive (anode) is usually 1cm proximal to the tip

Question 18

what do unipolar pacemaker leads have?

Answer 18

infer sued has one neg electrode in contact w heart and a positive extra cardiac electrode which is part of the pulse generator. the unipolar gives large ECG spikes easily recognizable bit is susceptible to interference from large groups of muscles (eg. pectorals)

Question 19

which pacemaker lead is more common?

Answer 19

bipolar bc generates a small EC spike but not susceptible to outside muscle interference

Question 20

what is the pulse generator?

Answer 20

includes the power source (or battery) and the electronic circuitry responsible for sending out appropriate timed signals or creating an electrical pulse and for sensing cardiac activity

Question 21

what is the catheter lead system?

Answer 21

connects the pulse genitor to the heart. it includes and insulted conductive wire

Question 22

where is the pacing catheter in relation to the heart?

Answer 22

it is in direct contact with the heart. usually the septal wall of the right ventricle. the pacing catheter delivers the electrical impulse to the myocardial and sense intrinsic cardiac activity. sensed intrinsic cardiac activity may inhibit or generate a pacing imupilse

Question 23

what is sensitivity?

Answer 23

define as the pulse generators ability to sense or see the persons own activity. dial of .8-20 mv. numbers represent amplitude of the QRS the pacemaker is ‘seeing’ so lowest is most sensitive. referred to as demand pacing

Question 24

(sensitivity) at the highest setting the pace will not sense intrinsic activity. this is referred to as?

Answer 24

asynchronous or fixed rate

Question 25

what is output/milliamps?

Answer 25

electrical activity delivered from the pulse generator through the pacing electrode to the myocardium to initiate depolarization. the amount of current delivered is measured in milliamps. the dial not he temp pacemaker inc in number as the output is increased.

Question 26

what is capture?

Answer 26

when sufficient electrical current or output is delivered to the heart muscle, depolarization occurs; this is known as capture”

Question 27

depolarization can also be caused by what? (other than the pulse generator) what is the name for this

Answer 27

by intrinsic cardiac activity occurring simultaneously w the pacemaker producing a complex called a fusion beat

Question 28

what does a fusion beat look like? when does it usually occur? is this dangerous?

Answer 28

has features of both the intrinsic and artificially paced morphology. can vary in shape or morphology depending upon which stimulus contributed most to depolarization

when pacemaker is close to own pt heart rate. not dangerous

Question 29

what is threshold?

Answer 29

the amount of elecrtrcal current required to cause depolization is called the threshold. determined by

-inc the pacing rate over the patients intrinsic rate so that paced rhythm can be identified or observed
-dec the MA or output while the paced rhythm is being observed to a point where the paced rhythm is no longer seen
the MA is inc again to the point that the pacemaker captures the ventricles and a paced rhythm is observed not he monitor. the point that pacing returns is known as the threshold

Question 30

what is encodcardial tissue fibrosis and what will this cause in re: pacemaker?

Answer 30

inflm response caused by the constant stimulation of the pacing catheter
irritated cardiac muscle cells have a dec response to electrical stimulation of 2-3 days which affects threshold and makes it ned for more electrical current (inc MA) to be delivered to cause depolarization. therefore, the pacemaker output is usually set 2 1/2 times higher than the threshold

Question 31

what is rate? how is it set?

Answer 31

number of electrical stimulation/min. ordered by dr. f pt is pacemaker dep, rate must be adequate to provide good CO. if pt is not dep then the rate is adjusted to a lower limit to provide back up and allow the pt to be in their own rhythm. dec incident of competitive pacing

Question 32

first pulse generators are at a field rate or synchronous which means what? what problem does this cause?

Answer 32

meaning electrical signals fire at a pre-set rate without regard for the patients own heart rate. this occasionally created a problem with competitive rhythms causing palpitations in some patients. also created the potential for the pacemaker to fire not he vulnerable period of the t wave and cause a life threatening dysthymia such as vfib. resolved w the development of sensing circuits that made demand (synchronous) pacemakers possible

Question 33

why are pacemakers in the synchronous or demand mode better?

Answer 33

they sense the patients intrinsic heart rate which prevents or suppresses the firing of the pacemaker when the intrinsic rate is greater than the set rate of the pacemaker

Question 34

what do temporary AV sequential apcemerks do?

Answer 34

they combine synchronous and asynchronous functions and the pacing leads are situated int eh atria and centricle and have the ability to pace both chambers

Question 35

is optimum sensitivity the same in all patients?

Answer 35

no it varies. dr must adjust. usually set at max or demand

Question 36

what is the escape interval?

Answer 36

it is the interval from the patients last beat to the first paced complex

Question 37

what is the basic rate interval?

Answer 37

the interval between paid beats, usually the escape and the basic rate interval are the same

Question 38

what is the fusion beat?

Answer 38

paced activity and patient intrinsic activity occurring at the same time

Question 39

what is the pacing spike?

Answer 39

artifact produced when the pacemaker fires

Question 40

what is the magnet rate?

Answer 40

results from placing a magnet over the pacemaker generator, this ‘turn off’ the sensitivity of the pacemaker causing it t function asynchronously. this is done occasionally n perm pacemekrst o test its pacing function as well as the magnet rate is indicative of battery life

Question 41

what is the magnet use with an ICD?

Answer 41

when ICDs are misfiring so when pt is in sinus tach, conscious with a good bp and device is firing. turns it off but does not disable pacing

Question 42

what is undersensing ? what is the soln?

Answer 42

pacemaker doesn’t pick up on intrinsic beats and competitively fires. may cause tachyarrythmias due to doubling of pt hear rate. and result in a pacing spike landing in vulnerable period of the t wave triggering V.F

SOln: dr order to inc sensitivity. if this does not sole the problem and the patients has a stable underlying rhythm, dr may order to turn off pacemaker

but if they do not have stable rhythm then may accept failure to sense and ask that it is monitored closely

reposition pacemaker (Dr)

Question 43

what is oversensing? soln?

Answer 43

if pacing circuity is too sensitive, it may inhibit from firing due to non cardiac electrical activity (eg. muscle movement) this can cause bradyarrhythmias

obtain dr order to dec sensitivity

Question 44

what is outside interference? soln?

Answer 44

pacemaker generators are better shielded than in the past from 60 cycle interference, i.e. from telemetry units, infusion pump or other equipment normally seen on cardiac ward. there is somer risk if OR if cautery machines, i.e. electrosurgery units are in use bc they emit electrical signals that a pacemaker may interpret as ventricular depolarization

soln: in pacemaker dep pt then turn the sensitivity off so that asynchronous or fixed pacing occurs

Question 45

different ways failure to capture will occur? soln for each?

Answer 45

catheter tip not in correct w cardiac muscle. the generator will not capture or depolarize the ventricles and this problem may be intermittent as the pacemker catheter floats in and out of touch w the muscle wall. patients with dilated chambers are difficult to position with tip floating out of position (gotta change the pt position and tell dr)

pacemaker is in area of damage and capture not possible. if this area becomes ischemic, cells will have a higher stimulating threshold (dr needs to inc MA)

marginally perfused cells which are exposed to antiarrythmic drugs will have higher thresholds (soln: with dep pt turned to left side and check all connections, or MA inc and battery replaced and if no work prepare for BCLS, ACLS, or another option is to opting he transcutaneous pacer from emerg and tell dr stat

Question 46

what is failure to capture?

Answer 46

emitted stimulus does not initiate depolarization

Question 47

what ifs allure to pace? problems? soln?

Answer 47

no evidence of pacing spikes- fi the patients intrinsic heart rate is above pacemaker rate and pacemaker is inhibited (this is appropriate so no problem)

but if patients intrinsic rate is below pacemakers setting then check generator make sure its on, check all connections change battery, change pulse generator and cable, if underlying rhythm is unstable be prepare for BCLS, ACLS, obtain transcu pacemaker and tell dr

Question 48

what are the indications for external transcutaneous or transthrroacic pacing?

Answer 48

provide v pacing quick to allow time to get temp pacemaker
noninvasive pacing here is good to Inc CO for patients with bradyarrhytmias, systole, conduction disturbances occurring with acute MI and for emerg support during perm pacer failure. also used in situations where pacing is needed on a standby basis for rhythms such as sinus pause, rbadycardias or 2 degree heart block type II

Question 49

method of external transcutaneous or transthoracic pacing?

Answer 49

pacing occurs via two large electrode pads placed over the precordium and on the posterior left side of the chest beneath the scapula. inc pulse duration and large electrode surface area provides lower current density requirements for capture.

when transcutaneously pacing, the Egg rhythm of the patient must be monitored independently with the 3 lead cable provided on the defibrillator. if the ECG leads are not attached, the unit paces asynchronously. the monitor screen shows a pacing artifact, followed by a wide complex if ventricular capture occurs

Question 50

what are the modes?

Answer 50

non demand, fixed or continuous pacing will occur continuously at selected rates regardless of the patients own intrinsic rhyth

Question 51

what is demand pacing?

Answer 51

pacing that sense the intrinsic QRSctivity and inhibits pacing stimulus for the cycle. or goes off when no intrinsic beat

Question 52

what is inhibited?

Answer 52

means the pacemaker does not fire when it senses pt rhythm

Question 53

what is triggered?

Answer 53

means that once a preset interval expires the pacemaker fires or paces the atria or ventricles