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Sunday, July 17, 2011

Holter Monitor Hook-Up: The "Fort Knox" Method

Hooking up a Boxer to a holter monitor -- a 24-hour ambulatory EKG -- has three main goals: One, record the dog's heartbeat for 24 hours; two, keep the electrodes attached to the dog's body for the entire 24 hours; and three, keep the dog from eating the wires that run from the electrodes to the monitor. To achieve these goals, proper hook-up of the holter monitor is essential.

Various holter hook-up methods have arisen over the years, as breeders have tweaked what does and does not work for their purposes. Holter vests are available for purchase, ranging from $50-200, that provide a pocket for the monitor and a covering over the electrodes. For most Boxers, especially with the super-sticky foam electrodes, a vest is probably adequate. This discussion will go a bit further, however, as our model has a special taste for holter wires and has chewed up two sets to date. For her, a vest does not work, because she reaches through the armholes to get to the wires. Thus the "Fort Knox" method was developed and, to date, has proven impenetrable. The process can be used with a vest, and we will note where a vest would be different from our method.

The first step, of course, is to gather all of your equipment together. Because we aren't using a vest with a pocket, we had to come up with a way to keep the monitor from sliding backward or to either side of the dog. The holter monitor we purchased from Alba Medical came with a case that has a loop on the back, so we attached that to a harness that the dog wears during the monitoring.

You will also need the holter monitor, lead wires (5- or 7-electrode, depending on the monitor), holter kit, and alcohol wipes for cleansing the area where the electrodes will attach. With a vest, this may be all you'll need. For Fort Knox, we also have a roll of VetWrap, some Zonas first aid tape, a child's onesie or t-shirt (size 24 months or 2T should work) and an adult t-shirt.

The holter kit, which we purchase from Alba, contains the cassette tape, 9-volt battery, patient diary, and StableBase electrodes. These electrodes are extra super-duper sticky, and have decreased the amount of tape we use when holtering by about 99 percent. They've also eliminated the need to shave the dog before attaching the electrodes. You will undoubtedly get an even stronger connection when shaving, but we haven't shaved for about 10 holters (on various dogs) and have only had one electrode come loose and no comments about excessive noise or unclear readings. Coated breeds should still be shaved, of course, but for our short-haired Boxers it is no longer a necessity -- provided you're using the StableBase electrodes. (We haven't tried other brands so can't attest to whether similar electrodes work as well.)

Holter kit from Alba Medical
Next, get your dog ready for the hook-up. A grooming table comes in very handy here; if not, it's best to have a helper to keep the dog steady while you're working. Attach the holter case to the harness and then put the harness on the dog. If you're using a vest, do not put it on the dog yet.

Dog on table, wearing harness with holter case attached. The monitor is not in the case at this point.

Next, cleanse the area where you'll be attaching the electrodes. (If your Boxer is very dirty, consider giving him a bath first, and be sure he's thoroughly dry before you begin hooking up the holter.) The electrodes will go along the rib cage, behind the back strap of the harness. Use an alcohol wipe to remove light dirt and the natural oils of the skin and hair.

Wipe the alcohol swab as shown, straight down to the belly of the dog. (Pardon the manicure!)

Next, attach the electrodes. Make sure the gel at the connection points is still wet; dry electrodes will not conduct a signal efficiently. Start at the bottom, as low as possible, and "stack" them vertically, keeping them even with a slight space between each electrode.  You will have an uneven number of electrodes on each side, either two and three (for a 5-lead monitor) or three and four (for a 7-lead monitor). We are using a 7-lead monitor on our model dog.

Dog's right side, three electrodes.
Dog's left side, four electrodes.
 Next, snap the lead wires onto the electrodes. You will have received instructions as to which wires go on which side, and in what order, when you purchased or rented the holter monitor or purchased the holter kits. Align the wires so they're pointing straight up to the dog's back, to keep them from escaping out the sides of the covering. (The StableBase electrodes have a slit on one side that is used to keep the wires in place on humans; since they are on the sides they don't function as efficiently for dogs, but if you prefer to use them for additional sticking power, just be sure the wires are fully covered in later steps.) Run the wires over the top of the dog when moving from one side to the other.

Lead wires attached, dog's right side.

Lead wires attached, dog's left  side.
Once the leads are attached, insert the battery and the tape in the monitor, in that order. The tape has a "bar" across the bottom that is opened to insert the tape, and closed two clicks to secure the tape and start it running. Make sure you see the tape turning before you proceed to the next step -- it moves slowly, but you can easily see it moving (and you may hear a quiet whirring, as well).

Tape inserted, gate open. (Note battery should already be installed.)
Closing the gate -- the arrows should line up when fully closed.

Tape and battery inserted, gate closed, tape is running.
Record the time you started the tape on the patient diary. You may want to record the time when you finished hooking up the monitor, as well; this can help identify any artifact at the beginning of the tape.

Close the cover of the holter monitor and place it in the monitor case. (If you don't have a case, you might want to tape the monitor closed as a safeguard.) Gather up the excess wires and gently and neatly stuff them into the pockets of the case. If you're using a vest, the monitor and excess wires will go into the pocket of the vest, in a later step. Get as much of the wire contained in the pocket or the case as possible.

Monitor in case. The excess wires go in the pocket on the top of the case, on the left in this photo.
For the Fort Knox treatment, wrap VetWrap around the electrodes, wires, and monitor. Cover all of the wires to provide an extra layer of protection. If possible, cover the monitor case from top to bottom to prevent it from sliding. We use a full roll to ensure adequate coverage.

VetWrap around electrodes, lead wires, and monitor. This was not a completely full roll, or the back of the monitor case would have been included in the wrapping.

If you're using a vest, you can probably skip this step, or you might want to wrap around the electrodes and wires before putting on the vest and placing the monitor in the pocket. If you have problems with the VetWrap sliding off of the electrodes, you could use Elastikon tape, which has an adhesive.

Ease the onesie or kid's t-shirt over the dog's head, underneath the loop of the grooming table arm, if applicable. Gently work the dog's legs through the sleeves. You may need to modify the onesie somewhat, by cutting off some of the arms or making a cut in the back of the shirt. If using a vest, put it on the dog as directed. Make sure the electrodes, lead wires, monitor and case, and VetWrap are all covered.

Onesie, taped at the bottom. Notice the modifications at the sleeves and back of the neck.

 Tape around the bottom of the onesie to keep it from flopping around or riding up. This is the only tape we use, except a small piece to secure the end of the VetWrap. Before the SmartTrace electrodes, we used nearly a full roll of super-adhesive Curity tape just to keep the electrodes on the dog. The Zonas tape is not as sticky; it will keep the onesie in place but won't pull all the hair off the dog when you remove it.

With a vest, tuck the monitor and as much of the wire as possible into the pocket. Add reinforcements if you'd like; otherwise you can skip down to the removal section.

Next, ease the adult t-shirt over the entire contraption, again gently putting the dog's legs through the sleeves. You can modify this t-shirt as well, if necessary, but a size medium or larger should not need any additional room. Gather the t-shirt at the bottom, well behind the end of the onesie, and secure with an elastic band or pony tail holder. For males, gather the shirt a little further toward the front of the dog, and try to keep the bottom as snug as possible. (He will probably get some urine on it, so don't use your favorite t-shirt!)

Gathered t-shirt held with pony tail holder.

Be sure the t-shirt is snug around the dog's waist.
Tie the gathered end of the t-shirt into a knot to secure it. If you don't have enough length to tie a knot in the gathered fabric as is, and are willing to modify the shirt, cut the gathered section down the middle and tie a knot in it that way. Tuck the knot underneath the shirt to keep the dog from chewing on it and opening it up.

Ready to go!
This system stands up well to the rubbing the dogs invariably do once they're off the table!
Removing the Monitor

If all goes well, the monitor and electrodes have stayed attached for 24 hours and the wires are still in one piece. Now it's time to remove the monitor, which is basically the reverse of hooking it up. Remove the t-shirt; untape the onesie and remove it (or remove the vest); remove the VetWrap -- if you cut it off, which is usually easier, be very sure you don't cut any of the wires. Detach the lead wires from the electrodes and remove the holter monitor and harness.

You're left with just the electrodes attached to your Boxer. The one disadvantage of the extra super-duper sticky SmartTrace electrodes is that you can't just pull them off the dog -- you're liable to remove all the hair and possibly some of the skin if you do. Use a hospital-grade adhesive remover such as Zo-Eze to thoroughly saturate the electrodes, and let it sit for a few minutes. (Saturate a cotton ball and rub/squeeze it along the edges of the electrodes to allow the remover to seep underneath.) You can sometimes then simply pull the electrodes off, but if they're still a little sticky saturate another cotton ball and wipe it right along the edge where the electrode is stuck to the fur, while gently pulling the electrode off. Always remove the electrodes in the same direction as the hair growth to minimize the amount of hair and skin you pull out.

Once the electrodes are removed, a brisk but gentle rub with a warm wet washcloth will remove traces of the adhesive remover, the electrode gel, and any adhesive residue. If a significant amount remains, the dog might need a bath. When you've finished, let your dog enjoy the freedom of being holter-less again.

All that's left now is to send the tape in for monitoring. Remove the tape and the battery from the monitor. Discard the battery (holter services recommend you always use a fresh battery with every holter). Write the dog's name on the tape label. Fill out the holter form, include payment, and mail the tape to the appropriate service. Alba sends pre-addressed padded envelopes for their service; we send those via Priority Mail with Delivery Confirmation, so that we can be sure the envelope gets where it's supposed to go.

Digital monitor readings can be transmitted over the phone or online, following the instructions from the holter service. If your phone or Internet service won't support the transmission, you can mail the flash card.

The patient diary is used to record any significant events or syncopal episodes. For pre-breeding screening, you generally don't really need to send in the diary, but it doesn't hurt to do so. Keep a copy for yourself, however, so that when you get the report back you can correlate the holter information to the dog's activity. Alba's turnaround time is generally 1-2 days after they receive your tape; other services may take longer.

Read more about basic holter monitoring information here. Stay tuned for information on reading and interpreting holter reports.

Happy holtering!

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