Temporary Epicardial Cardiac Pacing
30/11/10
PY Mindmaps
USES/INDICATIONS – post cardiac surgery
- conduction abnormality (bradyarrhythmias)
- tachycardia (AV junctional tachycardia, SVT, VT, atrial flutter)
- other: restoration of AV synchrony, HOCM to prevent SAM
DESCRIPTION
- produce electrical current with subsequent depolarisation + sensing function
Unipolar
- negative wire attached to the epicardium
- positive wire attached to subcutaneous tissues
Bipolar
- a single wire with two conductors insulated from one another which both run to the
epicardial surface
- smaller distance for current to run -> threshold less
- more suitable for dual chamber applications
- require less energy to begin with and may have greater longevity compared to unipolar
system.
METHOD OF INSERTION AND/OR USE
Jeremy Fernando (2010)
Typical Settings
- atrial and ventricular output 10mA
- lower rate 80/min
- atria and venticular sensitivity 2-5mV
- PR interval 150ms or ‘auto’ (determined by rate)
- PVARP 250ms or ‘auto’ (determined by rate) = post ventricular (pacing spike) atrial
refractory period
OTHER INFORMATION
Daily Checks
- assess underlying rhythm (turn pacemaker rate down and assess)
- test sensitivity (minimum current that the pacemaker is able to sense -> place in VVI,
AAI or DDD, increase sensitivity until the sense indicator stops flashing -> asynchronous
pacing should take place, then turn sensitivity down until sense indicator flashes which each
endogenous depolarisation -> this equals the pacing threshold -> set pacing generator at half
the pacing threshold)
- capture threshold (minimum output required to stimulate an action potential in the
myocardium -> set rate above native rate, then reduce output until QRS no longer follows
pacing spike = capture threshold, leave output at twice the threshold)
Jeremy Fernando (2010)
COMPLICATIONS
-
infection
myocardial damage
perforation
tamponade
disruption of coronary anastomoses
undersensing
oversensing
failure to capture
unstable lead position
Removal of wire
- gentle traction allowing cardiac motion to help dislodgement
- if they get cut, cut close to skin so they will retract.
MRI
- can’t have MRI’s c/o the amount of ferrous material in pacing box
- controversial regarding in situ epicardial wires
IABP
- if IABP is timed according to ECG with high frequency filter disabled (allowing pacing spikes
to become visible) -> pacing spikes can be misinterpreted by the IABP as QRS complexes
- IABP should be timed according the arterial pulse or the high frequency filter applied
- less problematic with bipolar leads
Jeremy Fernando (2010)