Temporary Cardiac Pacing

Historically this could be done via trans-esophageal route; these days, mostly is transcutaneous and transvenous.

Indications for Temporary Pacing

Post-Cardiac Surgery

Post-Myocardial Infarction

This clinical situation is informed by 2013 STEMI and 2014 NSTEMI guidelines, and 2012 PPM guidelines.

The culprit lesion/territory has important prognostic implications. Heart block from anterior AMI generally results from significant irreversible necrosis to the His-Purkinje system due to its location in the interventricular septum. Heart block from inferior AMI generally is vagally mediated and atropine sensitive (at least initially), and can also involve SA node dysfunction due to 90% of people having the sinoatrial nodal artery supplied by the RCA. This can lead to sinus bradycardia, SA exit block, and sinus arrest which are typically transient and atropine sensitive.

Indications for pacing post-AMI

  1. Asystole
  2. Symptomatic or hemodynamically significant bradycardia unresponsive to medical therapy (generally limited to atropine due to concerns about vasoactive medications increasing myocardial ischemia)
  3. Bradycardia-induced VT requiring overdrive pacing
  4. Anterior NSTEMI with new high-degree, bundle branch, bifascicular, or third-degree AVB (i.e. prophylactic pacing in this setting)
  5. Anterior/lateral STEMI with any presence of second or third-degree AVB, new BBB, or bifascicular block
  6. Irrespective of guidelines, always consider prophylactic transcutaneous pad placement in high-risk settings:
    1. alternative BBB
    2. RBBB + LPFB

Torsades de Pointes

TdP is a syndrome of bradycardia-induced polymorphic VT requiring three elements:

  1. Polymorphic VT
  2. Prolonged QT interval - which can be acquired or congenital
  3. Pause-dependent tachycardia initiation - generally during the compensatory pause following a PVC

In TdP, VT is generally nonsustained but rarely can degenerate into VF (a terminal condition).

Management of TdP

  1. Underlying problem
  2. If there is an underlying PPM, consider asking EP to rule out "R on T" pacing and if reprogramming the PPM can resolve the problem.
  3. IV MgSO4 (1-2 grams over 5-10 minutes)
  4. Correct hypokalemia as needed
  5. Consider isoproterenol infusion to accelerate the HR and shorten the QT interval (avoid in long QT syndrome in which this can precipitate arrhythmia)
  6. Avoid amiodarone (prolongs QT)
  7. Consider lidocaine if antiarrhythmics are required
  8. TVP is then indicated for refractory (to electrolyte supplementation and pharmacologic augmentation of HR) cases or with severe AV conduction issues predisposing to long-short initiation sequences. Temporary pacing shortens the action potential and truncates the post-premature PVC contraction pauses that trigger an episode.
  9. Pacing/heart rate augmentation at 90-100 BPM is typically sufficient to suppress ventricular ectopy, but rates as high as 140 BPM may be necessary
  10. If there is a PPM, then consider reprogramming to achieve the above target HR

Conditions which normally do not require temporary pacing

  1. Hypothermia
  2. Hypothyroidism (hormonal replacement is typically curative)
  3. OSA and bradycardia during sleep. Generally CPAP will abolish conduction defects - suggesting strongly that hypoxia plays an important pathophysiological role.
  4. Seizure-mediated ictal bradycardia
  5. Spinal cord injury

Transvenous Pacing

EM:RAP Placing a Transvenous Pacemaker - YouTube

Steps

  1. Single lumen CVC - Cordis Introducer Sheath - 6Fr
    1. Sites: R IJV (preferred) or L subclavian
    2. Remove wire + dilator together
  2. Plug the connecting cable (sterile) into the pacing generator (nonsterile) - venous connection as default
  3. Check the balloon with the syringe - can it inflate? Leave it deflated
  4. Feed the wire through the sterile sleeve (make sure the orientation is correct)
  5. Thread the wire into the Cordis - let the curve follow to the heart. Go until 20 cm mark (2 black lines) which indicates that the tip/balloon are just outside of the Cordis sheath
  6. Connect the adapter pins to pacing wire
  7. Connect the adapter pins to connector cable (negative to negative, positive to positive)
  8. ASSISTANT: turn on the pacing generator and set up (80 BPM, >5 mA venous. Default sensitivity = 3)
  9. Insert the wire to 30 cm
  10. Inflate the balloon
  11. Slowly advance the floating wire about 5 cm more - watch the monitor for "injury pattern" which confirms you are in the RV. Or, check using POCUS (need an assistant_)
    2. Check for mechanical capture - pulse or pulse ox
  12. Adjust the pacing generator - turn down sensitivity until we lose capture, then turn it up a bit again.
  13. Deflate the balloon and lock its stopcock in place
  14. Pull the sterile sleeve over to the Cordis and connect it into place
  15. Open the sterile sleeve up and lock it on the pacing wire
  16. Suture the line. Done!

Pacer Setup

Parts

- Pacing wire out the IJV - Sterile sleeve - Syringe for inflating/deflating balloon - Adapter pins - Connecting cable - Pacing generator

References

  1. Parrillo Critical Care Medicine - Chapter 5 (Cardiac Pacing)