Emergent Cardiac Pacing

Case

The 67 year old bradycardic patient from the previous case has a heart rate of 38 and a blood pressure of 68/45. It is time to start pacing…

Transcutaneous pacing^1,2

1. Apply the pads
   • The ideal position is anterior (just left of the sternum) posterior (at the inferior medial margin of the)
   • Do not place over an ICD or implanted pacemaker
   • Remove any drug patches
2. Activate the pacer
3. Set desired heart rate
   • Generally 70 or 80 is reasonable to start
4. Slowly increase output until capture is acquired
   • Electrical capture can be judged on the cardiac monitor. (Every pacer spike should be followed by a wide complex QRS complex.) However, assessing for mechanical capture is more important. Classically, this was done by feeling for a pulse and correlating the cardiac monitor with the pulse oximeter tracing. However, I prefer to watch for mechanical capture using bedside ultrasound.
5. Give pain medication

The amount of energy used to pace is less than 1/1000 of that used to defibrillate. There is little risk of injury to clinicians and, if necessary, chest compression can be done directly over the pads while pacing.¹

Transvenous pacing

Setting up

• Set the patient up as if you were going to perform a central line. The right internal jugular is the prefered location. The second best is the left subclavian. (Best, because they have the straightest approach to the right ventricle.)^1,3
• Perform the usual sterile preparation
• Consider the best way the anesthetize the patient. My suggestion is an ultrasound guided superficial cervical plexus block. It is quick, easy, effective, and uses only equipment you already have out
• Check the balloon for a leak
• Depending on your kit, you may also need to open a standard central line kit to get the other equipment you need, such as a scalpel, sutures, and extra needles.

Set up the pacing generator

• Ensure there is a fresh battery
• Set the rate (around 80, so that it is easy to determine when capture occurs)
• Set the output. Initially set the output to the maximum level, which is usually 20 mA.
• Set the sensitivity. This is the pacemaker’s ability to sense intrinsic heart activity. While placing the pacer, we don’t want it to sense the patient’s intrinsic cardiac activity. Start by having the pacer set to “asynchronous” mode, which means that the pacer will continue to fire at the set rate no matter what. Also have the sensitivity setting low (about 3mV).
• Attach the sterile patient cable to the pacemaker unit. You will need an assistant to handle the non-sterile equipment and tighten the thumbscrews. (Pro tip courtesy of Taming the SRU: hanging the non-sterile wire over an IV pole placed near the patient’s shoulder will allow the non-sterile wire to hang without falling onto the sterile field.) The proximal wire attaches to the positive port (Proximal = Positive).
• Attach the sterile sleeve before inserting the pacing wire into the introducer, so that it can be withdrawn and advanced sterilely (if necessary)

Inserting the introducer

This is done in same way that you insert a central line. If you are not already supremely comfortable placing central lines, placing a transvenous pacemaker is probably not a procedure for you.

Insertion with ECG guidance ^1,3

• Set up so you can easily see the ECG machine or cardiac monitor you will be using as you insert the pacing wire
• Use the connector or alligator clamp to connect the end of the pacer wire to one of the V leads on your cardiac monitor or ECG machine
• Insert the line about 15cm, then inflate the balloon with 1.5ml of air. Move the stopcock to the locked position. The balloon is supposed to help the line go in the direction of the blood (towards the right ventricle).
• Slowly advance the pacer wire while monitoring the lead it is attached to. The ECG changes are much better understood visually, but briefly:
  • In the atrium, the P wave will be large, and all the forces will be away from the tip of the catheter, resulting in negative Ps and QRSs
  • In the right ventricle, the P waves will be smaller and positive, the QRS will be negative and larger, and the T waves will be positive and larger
  • When the catheter touches the ventricular wall, the QRS and T waves will become much larger, and there will be ST elevation
• Deflate the balloon
• You may now celebrate (briefly)
• If you overshoot and need to pull the wire backwards, make sure the balloon is deflated.

Insertion with ultrasound guidance ³

Although ECG guidance is the classic technique, ultrasound provides an alternative (and in my completely non-evidence based opinion better) approach. Standard emergency POCUS views of the heart can be used to visualize the advancing wire, confirm its placement in the right ventricle, and confirm mechanical capture. The ultrasound must be used with sterile technique, or a second clinician can manage the ultrasound. A subxiphoid view probably provides the best visualization of the right side of the heart.¹ You watch for the linear, hyperechoic wire to enter the atrium and then guide it into the ventricle.

Blind insertion ³

Although not ideal, sometimes the urgency of the situation or the lack of equipment will mandate a blind insertion. After advancing the wire about 15 cm, set the pacemaker to “asynchronous” mode, set the rate at 80, and put the output at max (20 mA). Inflate the balloon. Advance the wire slowly, monitoring the ECG and the pacer sensing light. When electrical capture is witnessed, deflate the balloon and finish up. Never advance the wire more than 10cm once the sensing light comes on. If electrical capture is not obtained, withdraw the wire 10cm, rotate it 90 degrees and then slowly advance again.

Finish up

• Check for electrical and mechanical capture. (Again, ultrasound will be very useful here)
• Once the catheter is in the correct location, note the depth, ensure the sterile sleeve is fully extended, and secure the line in place
• Set the pacer at the desired rate
• Change the pacer the “demand” mode, so that it can sense the intrinsic heart activity and avoid R on T phenomenon
• Turn down the current until capture is lost. Set the output to 2.5 times this level (usually between 2-3 mA) to ensure consistent capture with the lowest necessary power
• Get a chest x-ray

Notes

The one absolute contraindication to transvenous pacing is a prosthetic tricuspid valve.¹

Other FOAMed Resources

Transvenous pacemaker placement on Taming the SRU

Identifying complete heart block on the use of temporary cardiac pacing in the emergency department on emDocs

References

1. Bessman E. Emergency Cardiac Pacing. In: Roberts JR, ed. Roberts and Hedges’ clinical procedures in emergency medicine, 6e. Philadelphia,PA: Elsevier; 2014.
2. Larabee TM. Chapter 31. Transcutaneous Cardiac Pacing. In: Reichman EF (ed). Emergency Medicine Procedures, 2e. Toronto: McGraw-Hill; 2013.
3. Reichman EF et al. Chapter 33. Transvenous Cardiac Pacing. In: Reichman EF (ed). Emergency Medicine Procedures, 2e. Toronto: McGraw-Hill; 2013.
4. Bing OH, McDowell JW, Hantman J, Messer JV. Pacemaker placement by electrocardiographic monitoring. The New England journal of medicine. 287(13):651. 1972. PMID: 5076460