The Pacemaker Series:

The Pacing Wire

The transvenous pacing wire is the very instrument that will be directing electrical Impulse to the heart, and so it is crucial that you are able to feed it to exactly where you want it.

Prior to placing the transvenous pacer, you will obviously need access if you haven’t obtained it already. Take a look here to get some guidance on venous access.

It’s always a good idea to familiarize yourself with your equipment outside of a situation of necessity as well as just prior to your insertion. In your transvenous pacing kit you will find the wire itself, 2 yellow electrode pieces, an alligator clip to attach to the ECG machine for identifying capture, and a custom-made syringe. This is important to pay attention to as the syringe is built to retract a fixed amount that is less than the syringe capacity. This guarantees that you do not over inflate the TVP balloon, since over-inflation and rupture introduces a significant amount of air into the circulation. Be sure to only use this syringe. Lastly, you will have your TVP sterility sheath that will be placed over the wire to keep it clean at all times, especially if you need to adjust the depth after all is said and done.

Once you have access in ideally the right internal jugular or left subclavian vein and you have tested your TVP balloon, slide the sterility sheath onto the TVP wire and leave it contracted. On the other end, make sure your yellow electrode pieces are inserted into the positive and negative ends of the wire and plugged into the ventricular port on the generator wire. To see how to set up the generator box, check out this video.

While your TVP balloon is deflated, pass the wire into the catheter until the 20cm mark is reached which is indicated by 2 black lines on the wire. This ensures the balloon has exited the distal end of the catheter into the vein. Once the wire is in, you can now lock the proximal end of the sterility sheath to the outer end of the introducer sheath, then unravel the sterility sheath along the length of the wire. This will now keep your entire wire sterile and the wire can now be advanced or retracted as needed without contamination.

At this point you can inflate the balloon and lock the stopcock to prevent deflation. With the generator box delivering an impulse, you may start to see small spikes on either the ECG machine if its connected or on the telemetry monitor. This indicates electrification of the vena cava.

Slowly advance the pacing wire with the balloon inflated so that it can follow the circulatory flow into the right atrium and then into the right ventricle. You can watch this video to help you identify where the wire is located based on the morphology.

Once you’ve identified the wire is in the right ventricle, you can deflate the balloon so that the wire doesn’t continue into the pulmonary artery, and after deflating the balloon, you can continue to pass it until it embeds into the ventricular wall.

Once this occurs, you can tighten the proximal knob of the sterility sheath until the pacing wire is clamped down and will not accidentally advance or retract. To make sure the distal end of the sterility sheath is secure as well, there is a knob to clamp down that end, too.

Now that the wire is pacing appropriately, your wire is locked into place, and your setup is sterile, you are done! All you have to do now is keep an eye on the patient’s heart rate and be vigilant if capture is weak or lost.

The Pacemaker Series:

The Generator Box

One of the most confusing parts about transvenous pacing is setting up the generator. Well not anymore.

Once you have access and have begun to set up your pacer wire insertion, ensure the distal end of the wire is connected to the appropriate positive and negative ports on the generator wire, and that the generator wire is plugged into the “V” port on the box. The “A” port is for atrial pacing while the “V” port is for, you guessed it, ventricular pacing.

Speaking of which, once you check for a new battery for the box, turn the generator on, test the locking button to ensure you are able ot later lock the buttons, and go to the knob for atrial voltage, usually denoted by an “A.” Turn this all the way down to zero; we won’t be atrial pacing in the ER.

On the “V” ventricular knob, set your desired heart rate to whatever your goal is. Typically aiming for 80-110 is usually a safe bet unless otherwise indicated.

Lastly, crank your output, or mA setting all the way up to max. This is usually between 20 and 30mA. By doing this, you are ensuring that the generator will output enough energy to capture and override any existing intrinsic electrical activity.

Once you’ve floated the wire into place as described here, you should see both electrical and mechanical capture, and at this point can begin to lower your output voltage. Drop your voltage incrementally keeping your eye on the actual mechanical heart rate, not just the electrical pulse, and identify the voltage at which point you just lose capture. Then immediately turn the voltage back up to the absolute lowest number that maintains capture, then double that number, and that will be your set voltage to maintain capture.

Once you’ve done all of this, hit the lock button to make sure no one accidentally changes anything, and hang the generator on the bed, usually on the IV pole hook so it’s easily reached and seen.

Now you know the generator box from beginning to end.

Also remember, at any point if you want to briefly examine the patient’s underlying intrinsic rhythm and rate, you can press and hold the “PAUSE” button on the generator. This will pause the generator for as long as you are holding the button without altering any of your settings.

The Pacemaker Series:

Venous Access

Prior to placing a transvenous pacemaker, one obviously needs to gain adequate access. Ideally, access is placed in the RIGHT internal jugular vein or the LEFT subclavian vein; access through either of these allows for a more streamlined approach given the anatomical pathway of each vessel, allowing a more direct path for the pacer to float.

The type of access is critical as well. Your transvenous pacing kit will usually come with an appropriate venous introducer sheath kit, but in case it doesn’t, be sure to obtain a venous introducer sheath, commonly referred to by its trade name “Cordis” and also ensure you have the appropriate French size. This ensures a large enough bore to fit the pacing wire but also not too large a catheter that might potentially allow bleeding and backflow around the pacing wire.

The process of inserting a venous introducer sheath is nearly identical to placing any central venous catheter, with a few caveats. The most important thing to remember prior to beginning your procedure that is different from a central venous catheter is that your dilator must be placed inside the introducer sheath, and both are passed over your guide wire as a single unit.

To review briefly, start by located the appropriate vessel with ultrasound, and after ensuring sterility, insert your introducer needle aiming for the desired vein. Be sure to begin applying negative pressure to the plunger once the needle has entered the skin.

Once you obtain a flash and have fed your guide wire into the vein through your introducer needle, create a nik that is large enough to allow passage of your dilator-sheath combo. After creating your incision, pass the dilator-sheath combo over the guide wire into the vessel making sure to hub the sheath.

Once you have done so, you can now remove the guide wire as well as the dilator out of the sheath, keeping the sheath in place inside the vessel. The one-way valve on the sheath will prevent backflow and at this point the sheath can now be sutured to the skin with the included suture needle.

That’s it! You now have large bore access for your transvenous pacer. Keep in mind, this is also the same procedure for inserting an introducer sheath for large volume resuscitation or any other procedure that requires an introducer sheath.