Veterinary Teaching Hospital

How To Apply a Holter Monitor a Horse

1. Cut or tear 10 pieces of white tape approximately 2 inches long.
Horse: Step 1

2. Snap the colored ends of the patient cable to the electrodes.

3. Shave 5 spots approximately 2 inches by 2 inches. 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 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 

Horse: Step 3

4. Prepare the monitor:

      a. With the monitor face down, cable connection towards 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.

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

Horse: Step 4

5. 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. 

 6. 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. 

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

Horse: Step 5, 6, and 7

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

Horse: Step 8

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

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

Start the Recording:

9. Turn on the monitor 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. 

10. 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. 

Horse: Step 10

11. Place the monitor into its protective pouch and lay it on the side of the withers. This spot is usually a slight little groove which 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 artifact to the reading. 

Horse: Step 11

12. 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. 

Horse: Step 12

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. 

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.


To remove the monitor – (please note the monitor will be off with a blank screen!)

Carefully remove the Elastikon. 
DO NOT USE SCISSORS!! It is far too easy to cut through the lead cables accidentally. 

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. 

You do not need to remove the flash card from the monitor, please leave it in place. Please remove and discard the battery. 

Please return any unused supplies. THANK YOU!
Washington State University