Unstable Bradycardia With TVP In Situ

Question 1

List steps to resolve a TVP that is failing to capture.

Answer 1

Visible pacing spikes are seen on ECG but no electrical capture on ECG or cardiac contraction seen in arterial line or Sp02 waveform. Usually due to some specific mechanical problem (wires no longer connected to heart, wires not tightly connected to cable, cable not connected to correct port, output setting to low)
Other causes: fibrosis at wire-myocardium
interface, MI, electrolyte imbalance, post-defibrillation, drugs (flecanide, sotalol, betablockers, lignocaine, verapamil)
Approach:
= correct exacerbating causes
= tight and confirm all external connections = increase output if possible
= bipolar leads may be tried in reverse positions or can try convert to unipolar pacing
= 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)

Question 2

List steps to resolve a TVP that is failing to sense.

Answer 2

steps to resolve a TVP that is inability to detect a depolarization event.
Due to specific setting of sensitivity.
Decrease absolute value of sensitivity (making it easier to inhibit)

Question 3

List steps to resolve a TVP that is oversensing.

Answer 3

Oversensing occurs when electrical signal are
inappropriately recognized as native cardiac activity and pacing is inhibited.
These inappropriate signals may be large P or T waves, skeletal muscle activity or lead contact problems. Abnormal signals may not be evident on ECG. Reduced pacemaker output / output failure may be seen on ECG monitoring if the patient contracts their rectus or pectoral muscles (due to oversensing of muscle activity). Usually due to settings on the pacemaker = increase absolute value of sensitivity (making it harder to inhibit).

Question 4

Lists steps to resolve a TVP that is failing to pace due to output failure (no pacer spikes on ECG).

Answer 4

Causes: lead malfunction, unstable connection, insufficient power, crosstalk inhibition, oversensing, apparent failure to pace

= check power, battery and connections
= increase output to maximum (25mA ventricular)
= switch to an asynchronous mode to prevent oversensing (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