Question 1

College answer

Syllabus topic/section:
2.1.18 Peri-operative issues in Intensive Care / Cardiac surgery: L1
2.1.19 Intensive Care procedures / Cardiac pacing: L1
Discussion:In general, candidates showed sound understanding of Transcutaneous pacing (TCP) and Transvenous pacing (TVP). Candidate are reminded to be accurate with the prescribing details, e.g. some mentioned setting in Joules, instead of current/ mA. Skin lead pacing was less comprehensively covered. Many candidates showed a suboptimal understanding of the topic. Given this technique is unique to cardiac surgical centres, familiarity with this technique may be lacking for some candidates. This may also reflect the lack of exposure in setting up the temporary pacing in real life practice. We advise candidates to practice in a simulation setting. A few candidates omitted the "Technique" part of the question and therefore, missed out on easily achievable marks. This illustrates how important it is to read the question carefully, so significant parts of the instructions are not overlooked. We recommend candidates highlight (circle/underline/highlighter) the key terms once reading time is over to assist with this cognitively. The better answers outlined the advantages and disadvantages with details on how they would affect the patient. The depth of this approach ensured a more successful display of the standard required as the candidate demonstrated WHY the detail was advantageous or disadvantageous. 

Discussion

Transcutaneous pacing:

• Technique
  • Broad conductive gel pads are placed ideally antero-posterior
  • or, worst case scenario, apex (V5) and right parasternal (V1)
  • Turn the defibrillator to pacing mode (choose VVI mode if the choice presents itself, as VOO risks R on T phenomena)
  • Increase the rate to the desired rate (80-90)
  • Increase the current to max (140-200 mA) for the unconscious peri-arrest patient; or increase in increments of 5-10 mA for the stable conscious patient
  • Confirm mechanical capture with pulse or arterial line
• Advantages
  • Widely available
  • Non-invasive
  • Requires minimal skill to implement
  • An improvement over ineffective medical or conservative therapy
  • Usually only a temporary measure
• Disadvantages
  • Requires skill to troubleshoot
  • Is uncomfortable and requires sedation
  • Can cause burns
  • Often ineffective despite pad position changes
  • Not a long term solution

Transvenous pacing:

• Technique:
  • An introducer sheath is inserted
  • The pacing catheter is floated like a PA catheter
  • Position is detected:
    •  With ECG connected (Lead 1), looking for the "current of injury". Or: 
    • With pacing on (eg. 10 mA) , advance and watch for capture
  • Confirm position using TTE, TOE, fluoroscopy, or just with a chest Xray at the end
• Advantages:
  • Relatively safe (as safe as a PA catheter, anyway)
  • Familiar ICU procedure
  • The same pacing pulse generator is used for this as for the epicardial pacing, which means staff do not need to be trained to use yet another piece of equipment
  • Can remain in situ for 5-7 days
  • Well tolerated
• ​​​​​​​Disadvantages
  • Not available everywhere
  • Requires expertise to place
  • Pacing infarcted tissue may not work
  • It may tangle with pre-exisitng pacing leads or various lines.
  • Placement is challenging when there is severe RV failure and TR

Use of a skin lead to continue epicardial pacing:

• Technique:
  • Insert the pacing stitch under the skin
  • Insert both of the remaining epicardial pacing leads into the negative terminal of the pacing box
  • Connect the new skin lead to the positive electrode
  • Pace as per usual (except probably with a much higher threshold, as the resistance to the flow of current will likely be increased by this).
• Advantages
  • Widely available and very quick (for the needle technique)
  • Minimally invasive
  • Requires minimal skill to implement
• Disadvantages
  • One of the other leads needs to be functioning
  • It may be uncomfortable and could produce muscle twitching
  • The impedance is increased, i.e. capture threshold is higher
  • Not a long term solution (perhaps 1-2 days is as long as you would be able to persist with this)
  • Easily dislodged