I called Guelph this morning to make sure Dressy was ready to come home. Talked to one of the vets on the case. He told me she was in good shape. Though he repeated again (with what I could tell was a bit of puzzlement) that she has a really pronounced second degree AV block. And again, I told him that she had always had it. I finally had to tell him that she’s rather notorious for it, and is in fact used as an example by the P/R crew at rides to teach beginners with a stethoscope what it sounds like. I told him that I’ve never ever listened to her at rest that she didn’t drop at least every fourth beat. He seemed to be mollified after that, and said it must be because she’s been so fit for her entire life.
I headed out with the trailer as soon as I got the okay. It was a much easier drive on a Sunday morning than Thursday morning. Rush hour through Toronto is unpleasant even with a car. With a truck and a 4 horse trailer, it’s very frustrating. So today’s drive was a big improvement. The trip was an hour and a half (as opposed to two and half on Thursday!).
The clinic was pretty quiet when I arrived. Just the weekend staff there. I got Dressy’s discharge papers and headed back to get her, but she was already being brought up. She came marching around a corner, with the student a bit more in tow than leading her. The vet gave me some instructions and a bundle of doses of potassium chloride to start her on.
Meanwhile, Dressy was dragging the student out to her trailer. We got to the parking lot and I was still chatting to the vet, so Dressy starting doing circles around the student. Zoom. Zoom… ZOOM. I finally had to stop talking and load her. Or really… just let Dressy barge up the ramp and back herself into her spot. “Put up the chest bar and let’s get this show on the road!!!” Dressy told me. The students and the vet were quite entertained by her performance.
This was a different batch of staff than the ones I met on Thursday. And so I got a whole new litany of compliments about Dressy’s wonderfulness. How good she was to work with, how sweet she is, how beautiful she is, and how obviously fit she looks. Dressy was not preening this time though. She was giving me her laser beam glare. “Move it, peasant girl! We have places to go! And horses to intimidate!”
This was a different vet than the one on the phone, and she again told me with a bit of puzzlement that the mare has a really pronounced AV block. So I again told her that Dressy is well known for this, and has always had it. AV blocks are not uncommon. But it seems to be less common for it to be so consistently apparent, even when she’s not completely relaxed. It works to our advantage in competition, especially in competitive trail where heart rates are scored. When her heart rate drops and starts skipping beats, she can quite easily get pulses below 40bpm.
We pulled in to a deafening chorus of neighs from her adoring subjects. King was the loudest of the lot. They obviously knew who was about to come off that trailer and were thrilled to have her home. I can’t imagine why, since she is not nice to any of them. But there they all were, ready to fawn all over her.
Getting her off the trailer was a bit of a scramble, since she was in more of a hurry than usual and I fumbled the rope and almost fell down keeping up with the big barging moose. She is in her stall now. Not happy that she’s not out dominating her minions, but more content than being stuck in the vet clinic I imagine.
If anyone is interested in technical details, here are some excerpts from her discharge paperwork.
Diagnosis: Atrial Fibrillation – resolved. Mild right atrioventricular (tricuspid) valvular regurgitation.
Tests: Physical examination, plasma troponin levels, venous blood gas and electrolyte analysis, packed cell volume, plasma total solids, echocardiography, electrocardiogram.
Treatments: Transvenous electrocardioversion (TVEC) under general anesthesia, sedation (xylazine and butorphanol), anti-inflammatory therapy (phenylbutazone), oral potassium chloride.
Exercise: The horse can gradually resume normal exercise regimen after five days of rest.
Diet: As usual, adapted to her exercise regimen.
Medication: Potassium chloride: Administer 50g orally twice daily indefinitely.
Follow Up: Please monitor the insertion sites over both jugular veins for increased heat, pain or swelling. If any of these signs occur, please contact your veterinarian as soon as possible. The amount of swelling present is normal for 48 hours post procedure. This needs to be monitored closely and kept clean and free of flies as much as possible.
Monitor the horse for signs of colic, depression, diarrhea or exercise intolerance. Please contact your vet if you have any concerns.
Here’s a description of the procedure:
Routine blood work was performed on the mare in prevision of the TVEC procedure and there were no significant abnormalities present. An intravenous catheter was placed in the mare’s left jugular vein. The horse was sedated with xylazine and two electrodes were introduced through the right jugular vein into the heart with the aim to position them in the left pulmonary artery and right atrium, respectively, under pressure wave form and ultrasound guidance. Once the electrodes were in place, general anesthesia was induced and a radiograph of the chest was performed to verify the position of the catheters. Cardioversion was successful at 250 KJ of energy. The horse recovered from anesthesia and was returned to her stall. She received phenylbutazone following the procedure. Serial ECGs were performed over the next two days to confirm that the horse’s heart is in sinus rhythm. There was a second degree atrioventricular block present with P-waves and no fibrillation waves. The mare remained bright and alert with normal vital parameters, ate well and passed normal manure for the remainder of her hospitalization. The amount of swelling over the right jugular vein is normal following the electrode introduction.