Temporary Pacemaker Problems

Temporary Pacemaker Troubleshooting

8/11/10 PY Mindmaps Will Young Tutorial on Pacing

GENERAL MANAGEMENT

- review rhythm strip and 12 lead ECG - check integrity of circuit (start at patient -> pacing box): lead placement, polarity, integrity, connected to right port of pacing box – atrial/ventricular, battery, settings - check mode - check rate - check capture threshold (find threshold and double it for safety) - check sensitivity (normal = 2-5mV) – changes with position - backup plans = transcutaneous or tranvenous pacing, atropine, adrenaline, isoprenaline, ephedrine, electrolyte replacement

Failure to Pace

= no electrical output at the pacing wire tips - causes: lead malfunction, unstable connection, insufficient power, cross-talk inhibition, oversensing (see below), apparent failure to pace.  check power, battery and connections  increase output to maximum (20mA atrial and 25mA ventricular)  switch to an asynchronous mode to prevent oversensing (AOO, VOO)  connect the pacemaker directly to the pacing lead (occasionally the connecting wires may be faulty)  prepare for transcutaneous pacing  prepare for CPR and chronotropic drugs

Failure to Capture

= no electrical out at the pacemaker tips (visible pacing spikes on ECG but no cardiac contraction seen in arterial line or SpO2 waveform) - causes: fibrosis at wire-myocardium interface, MI, electrolyte imbalance, post-defibrillation, drugs (flecanide, sotalol, betablockers, lignocaine, verapamil)  correct exacerbating causes  reverse polarity of both unipolar and bipolar systems may help  in bipolar leads, the negative electrodes develop fibrosis first -> use other electrode and plug into negative terminal and insert return electrode in the subcutaneous tissue (create unipolar circuit)  may need temporary transvenous wire

Failure to Sense

- produces atrial pacing when not appropriate - due to specific setting of sensitivity (including AOO mode)  same mechanisms as failure to capture and pace

Jeremy Fernando (2011)  decrease absolute value of sensitivity (making it easier to inhibit)

Cross talk

- in dual chamber pacing it is possible that the atrial pacemaker spike will be sensed by the ventricular wire and is misinterpreted as a ventricular depolarisation -> inhibits ventricular pacemaker output (ventricular standstill). - the opposite can happen as well.  reduce sensitivity in atrial or ventricular channel  reduce mA delivered to the ventricular or pacing wire

Pacemaker mediated tachycardia

- VDD or DDD pacing problem - can switch to VVI or DVI (but may loose AV synchrony)

(1) atrial sensing of a ventricular spike -> interpreted as an endogenous atrial depolarisation -> another ventricular impulse  use an atrial blanking period (now preset into box)

(2) retrograde conduction between ventricle and atrium through AV node or accessory pathway -> ‘endless’ loop of periodicity  adjustable post ventricular (pacing spike) atrial refractory period (PVARP)

Oversensing

- in DDD external electrical impulses can also be misinterpreted as atrial activity -> pacemaker mediated tachycardia  increase sensitivity threshold or switch to an asynchronous mode (AOO, VOO)

Jeremy Fernando (2011)