chap 10

Question 1

when complete heart block occurs at level of AV node the most rapid automatic activity arises from where and at what rate ?

Answer 1

the heart rate produced by the cells below the AV node usually relatively fast - often about 50 per min
= escape rhythm

Question 2

is pacing required in complete heart block ?

Answer 2

qrs complex may be narrow - in the setting of narrow complex CHB often may not require pacing - because HR not low and little chance of going into asystole

Question 3

causes of CHB ?

Answer 3

degenerative tissue fibrosis
anteroseptal myocardial infarction
cardiomyopathies
calcific valve disease

Question 4

automatic activity arising below the bundle of his due to CHB is likely to have what qrs ?

Answer 4

distal purkinjee - qrs complexes are broad

Question 5

pacing for CHB below bundle of hiss?

Answer 5

the escape rhythm is unreliable
and may fail - leading to syncope - stokes adams attack
or
fail completely causing ventricular standstill

= broad complex CHB requires pacing

if long ventricular pauses = make this urgent (>3sec)

Question 6

what in the egg strip can give an indication for successful pacing ?

Answer 6

presence of p waves

Question 7

in whom is pacing rarely successful

and most successful

Answer 7

asystole

during ventricular a-systole , there is still p waves due to ventricular stand still = pacing more likely to achieve cardiac output than in most cases of complete systole

Question 8

what is capture ?

Answer 8

is pacing stimulus induce immediate qrs complex

Question 9

what are the different modes of pacing ?

Answer 9

NON INVASIVE:

percutaneous - fist pacing

transcutaneous -does not provide reliable ventricular stimulation (discomfort for conscious patient)

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INVASIVE

temporary transvenous pacing

permanent pacing - implanted pacemaker

Question 10

when is percussion fist pacing used ?

Answer 10

succesful in ventricular standstill accompanied by continuing p waves

used instead CPR - produce adequate CO

Question 11

what inhibit the transcutaneous pacemaker ?

Answer 11

spontaneous QRS complex
movement artefact on ECG - if artefact still appears to be inhibiting pacemaker - switch pacemaker to fixed rate pacing

Question 12

appropriate pacing rate for transcutaneous pacing in adults ?

Answer 12

60-90 per min

but some circumstance with av block of ventricular rate of 50 - slower pacing to 40-30

Question 13

further adjustments in transcutaneous pacing ?

Answer 13

if pacing device has adjustable energy output
start at lowest first , gradually increase until each pacing spike is closely followed by qrs complex indicating electrical capture

always check if the qrs complex is followed by a t wave and palpable pulse (fails to create pulse = PEA)

if highest current setting reached and electrical capture not occurred - adjust the pads / electrode positions

continued failure to capture - hyperkalaemia ? non viable myocardium ?

when transcutaneous pacing provides adequate CO - senior input to switch to trans venous

Question 14

most transcutaneous pacing , paces the heart in what mode ?

Answer 14

in demand mode

Question 15

what are the disadvantages of transcutaneous pacing ?

Answer 15

conscious patient can experience a lot of discomfort
consider IV analgesia and sedation

NO DANGER FOR PEOPLE TO CONTACT PATIENT when patient being paced transcutaneous

Question 16

reasons why trans venous pacing failures

Answer 16

high threshold - need to place one f the electrodes on the apex of the right ventricle where it is least likley to be displaced
pacing threshold is taken by gradually reducing voltage
aim to achieve threshold <1 V at time of lead insertion
higher voltage means the elecytrode is not touching the myoicardium

usual to pace the heart with 3-4V well above the initial pacing threshold - transeint rise in pacing threshold over days is expected

check threshold daily so the voltage given is over the threshold i8f not loss of capture may occur - seen on ecg as pacing spike without qrs complex

sudden increase in pacing threshold , as you will see in the ECG as a loss of capture is due to displacemnt of electrode - ake sure to increase the voltage above the threshold , and obtain chest x ray to see where the electrode is

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Connection failure

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Lead displacement
Lead is usually positioned in the base of of the right ventricle - there should be enough slack in the lead to allow for changes in patient posture and deep inspiration.

when lead displaced in the right ventricle can lead to vf and Vt

Question 17

can patient with tranvenous pacing go into cardiac tamponade

Answer 17

very rarely yes

Question 18

with no pacing there can be ?

Answer 18

ventricular standstill = short lived cause - syncope

long standing - cardiac arrest

Question 19

is there is a patient with with an implanted SC pacemaker or ICD and requires electric carduoversion what do you do ?

Answer 19

place defib pads - 8cm fro the device

devices are usually implanted below the clavicle - and these devices have no problem with the use of standard defib

Question 20

what happens when a pacemaker ICD is places below the right clavicle instead of left or just below the axilla?

Answer 20

use AP position for defib

below right clavicle devices are usually leadless

Question 21

problems with implanted permanent pacemakers

Answer 21

lead displacement may occur as an early complication , BUT RARELY OCCURS 4-6 WEEKS AFTER

MISDIAGNOSE AN ARRYTHMIA MISINTERPRET OTHER ELECTRICAL SIGNALS and deliver inappropriate hocks

Question 22

what s the difference between simple pacemaker and ICD ?

Answer 22

simple ICD can deliver shock when it detects fast VT or VF

many devices programmed to also deliver critically timed pacing stimuli to prevent these sort of arrhythmia

Question 23

when’d o we resort to defib in ICD ?

Answer 23

when VT accelerates and degenerates into VF

Question 24

indication for icd ?

Answer 24

HIGH RISK OF VF

MAY IMPROOVE SURVIVAL IN PATIENT WITH MASSIVE MYOCRADIAL INFRACTION

Question 25

how to temporarily disable ICD?

Answer 25

holding ring magnet overlying the device usually above the pectoral

Question 26

cardiac arrest with ICD

Answer 26

DO CPR
= reports of transient myalgia and parathesia from the shock of ICD to the person doing CPR

if this decreases the quality of CPR - consider deactivating the ICD

if shockable rhythm present and not terminated by ICD = defib = BE CAREFUL WITH THE PADS

Question 27

f person dies with active ICD ?

Answer 27

arrange for deactivation of ICD
must be removed before cremation

Question 28

When using transcutaneous pacing:
electrical capture typically occurs with a current of?

Answer 28

50-100 mA