10. Cardiac pacing

Question 1

intrinsic rate produced by
1) SA node
2) AV junctional region
3) distal His-Purkinje fibres

Answer 1

1) 60-70
2) 40-50
3) 0-30

Question 2

T/F: in CHB the QRS complex will always been wide

Answer 2

false - when CHB occurs at the level of the AV node, the cells immediately below the block become the new pacemaker and normally beat about 50/min - narrow QRS as its rapidly conducted to the ventricles through an intact bundle of His

Question 3

when automatic activity occurs lower in the distal purkinje fibres, this leads to slow and unreliable rhythm - this escape rhythm may fail transiently leading to syncope called ___ ___ attack

Answer 3

stokes adams attack

Question 4

T/F: broad complex CHB requires cardiac pacing

Answer 4

true - urgently if there’s long ventricular pauses (>3s)

Question 5

T/F: pacing is rarely successful in asystole

Answer 5

true - do not routinely attempt pacing in the absence of p waves

Question 6

if a pacing stimulus induces an immediate QRS complex this is referred to as ‘_____’

Answer 6

capture

Question 7

pacing may be classified as
1) non-invasive e.g. …
2) invasive e.g. …

Answer 7

1) percussion (‘fist’ pacing), transcutaneous
2) temporary transvenous pacing, permanent pacing

Question 8

how to perform percussion pacing? (do if bradycardia so profound it causes clinical cardiac arrest)

Answer 8

with the side of a closed fist deliver repeat firm thumps to the praecordium, just lateral to the lower left sternal edge - raise the hand about 20cm above the chest before each thump

check for pulse and QRS complexes on the ECG
if no pulse start CPR

Question 9

major disadvantage of transcutaneous pacing?

Answer 9

causes discomfort in a conscious patient

Question 10

ideal placement of pads for pacing?

Answer 10

ideally the conventional right pectoral and left apical positions

if not possible use AP positions

(if using a pacing device that is not capable of defibrillation, use AP position for pacing pads so defib pads can still be applied)

Question 11

T/F: if there is significant movement artefact, change the pacing device from demand mode to fixed-rate pacing

Answer 11

true

Question 12

an appropriate pacing rate is normally what for adults?

Answer 12

60-90/ min

(slower in CHB)

Question 13

when doing transcutaneous pacing, continue to increase the energy until what is achieved

Answer 13

until each pacing spike is followed immediately by a QRS complex, indicating electrical capture

(ensure the QRS is followed by a T wave so you know its not artefact)

Question 14

what to do if the highest current setting is reaching in transcutaneous pacing and electrical capture has not occurred?

Answer 14

try changing electrode positions

continued failure to achieve electrical capture may indicate non-viable myocardium or other conditions e.g. severe hyperkalaemia

Question 15

good electrical capture that fails to generate a pulse constitutes what rhythm?

Answer 15

PEA

Question 16

T/F: there is no hazard from transcutaneous pacing to people who are in contact with the patient

Answer 16

true
although there’s no benefit to giving pacing during CPR so best to turn off

Question 17

what are the three ways in which temporary transvenous pacing systems can fail?

Answer 17

1) high threshold (usually paced at 3-4V stimulus, well above the initial pacing threshold which is aimed at <1V
2) connection failure
3) lead displacement

Question 18

when a temporary pacing lead is inserted, the usual aim is to position the tip where in the heart?

Answer 18

in the apex of the right ventricle - where it’s least likely to be displaced

Question 19

what to do if there is a sudden increase in the threshold of a tranvenous pacer

Answer 19

get a CXR to check the lead placement - as this may be caused by displacement and need repositioning

recheck pacing threshold if theres a loss of capture

Question 20

what is the pacing ‘threshold’ of a tranvenous pacemaker

Answer 20

the minimum voltage required to stimulate the ventricle

Question 21

most tranvenous pacing leads are UNIPOLAR/ BIPOLAR

Answer 21

bipolar

Question 22

what possible cause should be considered if a patient with a recently implanted pacing lead suffers a PEA arrest?

Answer 22

cardiac tamponade caused by perforation of the right ventricular wall

Question 23

T/F: when displacement of a pacing lead or perforation of the ventricle occurs, the ECG will still show a pacing spike

Answer 23

true - but there is likely to be intermittent or complete loss of capture of the pacing stimulus

Question 24

if a pt with an implanted s/c pacemaker or ICD has a cardiac arrest or requires cardioversion, place the defib pads >____cm fro m the device

Answer 24

8

Question 25

what is the primary function of an ICD?

Answer 25

to terminate a life-threatening tachyarrhythmia

Question 26

how can an ICD be disabled temporarily if it misfires causing discomfort to the patient?

Answer 26

place a ring magnet over it

Question 27

T/F: an ICD must be deactivate prior to its removal from the body/ an autopsy

Answer 27

True