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  Discussion on Congenital heart defects
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Posted on Monday, Apr 30, 2001 - 11:49 pm:

Hi:

I've been watching my 11 day old filly for over a week now because things just weren't "normal", but I couldn't put my finger on it, and discussions over the phone with our vet were not satisfactory in my mind. She would nurse well, her eyes were bright, ears perky, capillary refill was <2 seconds, yet, she was tachypneic with costal retractions (lungs were clear), nasal flaring, with resting heart rates at about 140 and respirations 60-80/minute. Finally, it dawned on me to listen to her heart tones a couple days ago,(duh!!) and that revealed a holosystolic murmur in the mitral area. The vet came out and confirmed this......drew lab work.....CBC and Chemistries were all normal. We're waiting for the equine cardiologist from the UofM to get back to us, but in the meantime I'm wondering about a few questions I have. A few things were brought up as far as possibilities......mitral insufficiency being most common, then Tetrology of Fallot, and Ventricular Septal Defect. With the later 2 conditions, would the foal not show signs of cyanosis? With mitral insufficiency wouldn't it typically be associated with rahls in the lungs? I've heard some foals have mumurs at birth. I don't know the severity of these murmurs, but is there a time period when they resolve themselves? My filly seems to be quite symptomatic with any activity (increased respiratory and heart rate), and her murmur does span the entire cardiac cycle. Any info would be appreciated. Having just lost a mare and foal 3 weeks ago to a uterine torsion, I'm thinking my love for horses should be limited to pictures of them.

Thank you,
Lynn

Posted on Tuesday, May 1, 2001 - 5:31 pm:

addendum to previous message: Twiggy died a couple of hours ago. The cardiologist at the University feels it was probably Tetrology of Fallot, but will be doing a post to know for sure. If this was Tetrology of Fallot, can you tell me if this is a genetic thing, or rather just a congenital fluke that happened during fetal development? I guess if there is anything to learn about this, even though we lost our Twiggy, I'd sure like to know.

Thank you,
Lynn

Posted on Tuesday, May 1, 2001 - 7:02 pm:

Lynn

My condolences on your recent losses. I too have lost two horses in the last three weeks due to a horrible dystocia and a freak accident where the mare kicked in the paddock and broke her 3 week old foal's leg above the knee. I am really questioning myself especially since we try our absolute best and seem to have bad luck. I always see negligent horse owners who seem to luck out and have no problems when they seem to tempt fate. I know of many relatively intelligent people who believe that a mare doesn't need to be monitored during foaling. They always come out into the barn to a surprise foal without problems EVER. Some people have the most unsafe fence and the horses don't ever get caught in them while we use diamond mesh and hot wire and keep our fingers crossed. I can only say that you are not at fault in either of those instances that you described.

Hope that you have some good luck in the near future, you deserve it!

Katherine

Posted on Wednesday, May 2, 2001 - 6:00 am:

My condolences Lynn,
When I read your first post I had already composed a reply: heart murmurs or certain grades and consistancies are considered normal in the foal up to several months of age and for the first week foals ocassionally have up to a grade 4 murmur. Many people do not realize that fetal circulation is different than that of the newborn. Blood is shunted at several locations from away from the lungs (pulmonic circulation) as they are not funtional in the womb. The valves close at birth or shortly after. Foals frequently have delayed closure of the ductus arteriosus resulting in up to a grade 4 murmur that generally disappears by day 4. Some foals have persisitent low grade heart murmurs but otherwise are healthy.

So, when I read your second post what a shock. For those who do not know tetralogy of Fallot is a set of congenital cardiac defects including ventricular septal defect, pulmonic valve stenosis or infundibular stenosis, and dextroposition of the aorta so that it overrides the ventricular septum and receives venous as well as arterial blood. Right ventricular hypertrophy is common.

In humans the cause of Tetralogy of Fallot is better understood and what emerges is a complex disease with a variety of causes. (ToF) is the most common form of complex congenital heart disease, occurring in approximately 1 in 3000 live births. It is certain that some of these are inheritable conditions (22q11.2 chromosomal deletion) while others appear to be mutations that occur in utero. I suspect the same sort of complexity occurs in the disease of horses.

Currently there are no reports or investigations into whether this is a genetic disease or not in horses. I do not know of any reports of this happening to certain stallions or in certain lines of horses.

I think it is important that if you are concerned about this you should have an aotopsy done so that the exact defect is known. The cardiologist may have unpublished information on this and I would love to know what his thoughts are on this.
DrO

Posted on Wednesday, May 2, 2001 - 8:58 am:

Dr. O:
Thank you for your reply. How Twiggy lived as long as she did with a disorder of this magnitude is beyond me. The will to live is truly miraculous. It makes sense now why I didn't notice any rahls in her lungs. I still don't understand why her capillary refill was so good, but then again, I only checked it while she was at rest. Also, the "nice little belly" she was getting I would imagine could be contributed to ascites due to the portal hypertension. She also had JVD like I'd never seen before in animal or human. Things seem a bit clearer today. I brought her to the UofM last evening and the cardiologist will be evaluating the cause of death for my husband and I. I will certainly ask her if she has any further unpublished information and pass that on to you.

Thank you too, Katherine, for your kind words. My condolences to you in your losses this spring as well. These critters, no matter how long they're with us, sure become a special part of our lives.

Thanks again,
Lynn

Posted on Friday, May 4, 2001 - 10:34 am:

Dr. O:

I received a phone call from the cardiologist yesterday afternoon. She said on autopsy, Twiggy's heart "looked normal". What?????? I know what I heard and the symptoms I saw......the vet also confirmed this. Major vessels were where there were suppose to be, there was no VSD. I asked about the conditions of her valves....particularly the tricuspid. She said it's difficult to tell about valves because there's no blood circulating on a post to note any regurgitation or stenosis. I find this very hard to swallow.....valve disease can be picked up on humans during autopsy.

There was ascites present, she said, and as for her lungs, it showed no increase in fluid there. I asked with the symptoms she displayed of exercise intolerance, tachypnea, tachycardia, nasal flaring, ascites and positive JVD wouldn't this indicate a right sided failure?? She said, not necessarily. Huh?

I asked if she had seen Twiggy a week before, what might she have done. She indicated she would've placed her on some Lasix. Again, I asked, "Why? If the problem isn't her heart, why couldn't she handle the current circulating volume?"

For lack of any other diagnosis, they're calling it "myocarditis". Twiggy's lab work, chemistries, protein, CBC, serum osmolarity were all "within normal limits" one day prior to her death. I understand that a viral myocarditis wouldn't probably show on lab work, but would that produce these types of symptoms? My husband is feeling they did the autopsy on the wrong foal.....nothing seems to be matching up, other than the ascites.

She did recommend a Vitamin E and Selenium level on Twiggy's dam. I asked if there was any visual indication of white muscle disease, and she said no, but that they have seen quite a few cases already this spring. Again, this makes no sense to me. Twiggy was putting on muscle before her death....we weren't seeing an atrophy. Granted, with her lack of activity, it wasn't a huge amount of muscle, like our colt, but I guess I didn't expect it to be. Tissue pathology is pending, although she indicated no gross abnormalities of muscle or tissue on visual exam.

I'm so frustrated. Any thoughts?

Lynn

Posted on Saturday, May 5, 2001 - 4:25 am:

Hello Lynn,
On necropsy the only abnormality was ascites?
DrO

Posted on Saturday, May 5, 2001 - 9:56 am:

Hi Dr. O:
Yup. I'm beginning to think my husband was right that they did the necropsy on the wrong foal, which, what the heck, we're all human, could happen. I didn't ask for a description of what the foal outwardly looked like. I'm sure they get many horses/foals through this large animal hospital. There were absolutely no signs of any heart defects. I did specifically ask if there was any right ventricular hypertrophy. It was indicated to me that she was at too young of an age to show any signs of that. (???) I also asked if an arrhythmia such as a continuous atrial fib with rapid ventricular response could lead us to these types of symptoms? It still doesn't explain the JVD, the thrill and the seemingly high pulmonary pressures to give ascites, but that's just my opinion. Her pulse felt regular to me, but at such high rates, I think sometimes it's difficult to tell without a rhythm strip to go by. I believe I also should've heard rahls in her lungs if that were the case.

They can tell me it wasn't her heart, but I just don't buy it. Guess I just have to let it go, and "stop beating a dead horse." The most important thing I have to keep reminding myself of, is that Twiggy is no longer struggling....that's really what's most important. I'm grateful for the days I did have with her.

I know you're only hearing my assessment of Twiggy, and it must be difficult to format a reply. My posts tend to get wordy, but I just don't want to leave anything out.

Sincerely,
Lynn

Posted on Monday, May 7, 2001 - 7:31 am:

I do think you misunderstand the labs position some Lynn. They are not saying your foal did not have heart disease, they are saying that it is not obvious from the post that this was present. There can be congenitial nerve conduction problems that would not show on the post but show the symptoms you have and might eventually result in death. On the other hand I think you are right to try and nail this down as firmly as possible. Perhaps their will be some defects in the myocardium that will show up on histiopath...

Was the ascites remarkable? I wonder how carefully the liver circulation was looked at, much of it is hidden deep in the tissue. If the liver has congenital stenosis of the the hepatic circulation if can result in ascites and a build up of toxins that do not show easily on the most commonly done lab tests.

Take the selenium recommendation to heart, if you live in a deficient area. The growth you saw the first week or two does not rule it out and in a mild case the symptomology from the heart might be all you would see. Ascites is also common in selenium / vitamin E deficiency and I am not sure it all comes from heart dysfunction.
DrO

Posted on Monday, May 7, 2001 - 11:11 pm:

Thank you for your reply, Dr. O.

In regard to the ascites.....no, it was actually quite minimal. I believe that digging real deep into the hepatic circulation wasn't done. The cardiologist was more interested in examining her heart, and just mentioned the abnormality of ascites was present. Guess we'll just wait on the pathology report.

I appreciate you taking time to help try to figure this out. We will have a Vitamin E and Selenium level drawn on our mare to r/o any deficiency, although our area hasn't had any problems. Guess it's more for my piece of mind than anything.

Thanks!
Lynn

Posted on Thursday, Jun 14, 2001 - 5:51 pm:

Hi Dr. O:

Received the pathology report on Twiggy today, and thought I'd share it with you.

Gross exam: Respiratory: There was a copious amount of thin, light-yellow cloudy fluid in the thoracic cavity. The lungs were red, palpably heavy and wet.

Cardiovascular: There was approximately 200 ml of serosanguineous fluid in the pericardial sac.

Alimentary: There was a large amount of thin, yellow, cloudy fluid in the abdominal cavity. The muscosa surface of the granular stomach was congested.

Diagnosis:

1. Pleural effusion
2. Pericardial effusion
3. Ascites

The cover letter from the cardiologist indicated that the fluid was not infectious in nature.

Just thought I'd pass this along.

Lynn

Posted on Friday, Jun 15, 2001 - 12:47 pm:

Have they done any biopsies?
DrO

Posted on Saturday, Jun 16, 2001 - 3:23 am:

Dr. O:

No....no biopsies were performed. I was under the impression when I brought Twiggy to the University that a full necropsy would be performed, but I was mistaken. They basically just did a visualization, without any histology or biopsies, so there's really nothing more to go by. :-( Looks to be a guessing game at this point. Cause of death was listed as "unknown". I wish I could give you more information. I'm sure it'd be difficult to comment on the limited information given.

Lynn
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