How to fit a horse with a Holter monitor


1. Cut or tear 10 pieces of white tape approximately 2 inches (5 cm) long

Strips of tape, cut and ready to apply.

2. Shave 5 spots approximately 2 inches x 2 inches (5 cm x 5 cm)

The first spot should be about 1/3 of the way down from the withers but back far enough behind the elbow so the front limb movement will not disturb it. Directly below that spot another 1/3 down the chest and about 4 inches (10 cm) behind the elbow is the next spot. These shaved areas should line up fairly straight with each other, so the cable is not stretched too far. Repeat these locations on the other side of the horse and put a fifth spot in alignment with others, just to one side of the withers.

Make sure that each spot is well shaved by shaving against the hair. Try to keep the spots symmetrical on either side of the horse.

If you plan on saddling the horse during the recording, consider the saddle and girth strap’s locations while deciding where to place the leads.

Series of 3 images showing where to shave patches for electrodes.

3. Attach cables to the patches

Snap the colored ends of the patient cables to the electrodes.

Monitor, cables and electrodes.

4. Prepare the monitor

With the monitor face down, cable connection toward you and the words Trillium 5000 at the top, the left side of the monitor is where the memory card has been inserted for you. You will not need to access this compartment.

5. Red electrode

The right-side door is for the battery. Open the battery compartment and insert a AA battery, observing the polarity diagram in the compartment. Securely close the battery compartment.

Back of monitor showing battery compartment.

5. Attach electrodes to the horse

Continue down the left side of the dog. Place the brown electrode in the same manner as the red electrode.

Remove the white electrode from the backing and stick on the spot near the withers. If you are using electrode gel or paste, a small dab of gel should be placed on the sticky gel center of each electrode before applying. Take two pieces of white tape torn earlier and place over the sides of the electrode. Do not cover the colored part, just the back of the sticky electrode.

Electrodes being attached on the left side of the horse, with 2 pieces of tape applied to secure them.

Proceed to the next shaved patch down the left side of the horse. Attach the brown colored electrode to this spot and place two pieces of white tape to either side of the electrode.

Continue down the left side of the horse. The next electrode to be placed in the same manner as before is the red one.

Lay the tape loosely onto the horse, do not pull or tug it tightly.

Go to the right side of the horse. The colors on this side go green then black, with green being placed on the highest patch and the black being placed on the lowest patch.

Electrodes being attached to right side of horse, with 2 pieces of tape being applied to secure.

The green electrode is the ground. It is very important for this lead to be attached well to the horse’s skin to get a good reading.

6. Secure with Elastikon

Note: Do not pull too tightly as Elastikon stretches and you could make it too tight around the horse.

The lead wires and cable should then lay forward so they are sticking out toward the neck while the Elastikon is taped on. Place a strip of Elastikon over all the electrodes and the white tape. Hold the end against the horse’s body while unrolling the Elastikon and continue to stick it to the horse while unrolling it. Wrap the Elastikon all the way around the horse. Once the Elastikon has been placed, it can lay loosely onto the horse, but you should firmly press down on it over the areas with the electrode to help keep the patches and electrodes in place.

Start the Recording

7. Turn the monitor on by pushing any keypad button

The first screen will ask you to input a patient ID number. Ignore this screen and scroll to the right using the → button. You should be able to see the ECG tracing on CH1, push the → button again to see CH2, again past CH3 and the SETTINGS menu until you get to the DATE/TIME menu. If the date and time are correct, press the ⤶ button. Use the up and down arrows to move to the item that needs to be corrected. Use the left and right arrow key to change the time or date. Press the key again to accept the changes.

All electrodes attached, and wrap applied to secure. Monitor being held at withers.

Start the Holter recording by using the right arrow key to move over to the START menu, then press the ⤶ key to start the recording.

All electrodes attached, and wrap applied to secure. Monitor being held at withers.

Place the monitor into its protective pouch and lay it on the side of the withers. This spot is usually a slight little groove that will protect the monitor if the horse rolls or rubs at the monitor. Try not to “kink” the patient cord as this too can add artifacts to the reading.

Monitor inside pouch and being held at withers.

8. Secure the monitor

Cover the monitor with another layer of Elastikon. It is usually ideal to wrap the Elastikon completely around the belly one or two more times to keep the monitor from slipping out as the horse moves around or rubs on things.

9. Apply the Holter vest

Another layer of wrap being applied to secure monitor at withers.
Final image of monitor attached and secured.

Remember: These monitors were designed for human use so it is important to secure everything that can open, move, or disconnect. This will allow your horse to perform normal daily activities without the likelihood of disturbances in the reading.

Final Notes

The monitor needs to remain running for at least 24 hours. While wearing the monitor we encourage you to let your horse participate in normal daily activity. The only things your horse cannot do is get bathed, perform excessive exercise that would cause sweating or stay out in the rain/snow for prolonged periods.

Note: the monitor will be off with a blank screen

Removing the Monitor

  1. Carefully remove the Elastikon. DO NOT use scissors. It is far too easy to cut through the lead cables accidentally.
  2. If the patient ECG patches did not come off with the Elastikon, carefully remove them from the patient. Discard any tape, Elastikon and the ECG patches.
  3. You do not need to remove the flash card from the monitor, please leave it in place. Please remove and discard the battery.
  4. Please return any unused supplies.