Liz Bode

Hi Scott,

Thyroid and cardiovascular function are fascinating – I love the fact that thyroid hormones have such a wide ranging affect on the heart.

I think if you hear a gallop or an arrhythmia in any cat, hyperthyroid or not, that they should be investigated for heart disease if possible. A cat with a murmur too, ideally, although as you know not all cats with a heart murmur have heart disease and cats without a heart murmur may also have heart disease!

In our clinic we have radioiodine therapy and all cats coming through have an echo. This is to try and pick up the ones on the verge of heart failure and who are, therefore, not suitable for treatment. I’d say (and this is a very rough estimate), that 85% will have concentric hypertrophy, 5% will have normal heats, 8% will have dilated atria and the rest will be in heart failure. The tricky thing with the cats who have changes is that you don’t know how much is due to the hyperthyroidism and how much is primary HCM. In order to know this further echo would be needed 6months or so after control of the hyperT4.

It’s sad though for the cats in CHF and their owners.

Hope that’s useful.

Liz

Replying to scott@vtx-cpd.com 11/04/2022 - 16:06

Hi Joyce,

This is a great question.

I am not aware of any literature in the veterinary world that suggests we should be setting the target TT4 value at a lower level than in other hypothyroid patients. However, I do think we have to be careful about how we supplement these patients and, sometimes, we may not be able to go all guns blazing straight away. I think this is particularly true in hyperthyroidism. I have certainly seen cats where we have treated the heart failure and hyperthyroidism as normal but this has then unmasked severe renal disease and, ultimately, ended up in euthanasia of the animal. Therefore, I approach these cases slightly less aggressively these days. Obviously, we need to control the congestion but perhaps using furosemide slightly more cautiously together with reducing the thyroid levels more gradually would make sense.

In dogs with hypothyroidism we rarely see severe heart disease. However, if you did it would be pertinent to start more cautiously with levothyroxine. So go lower with the starting dose and titrate up more gradually until euthyroidism is reached. The reason for this, although rare, is that levothyroxine treatment in people can precipitate coronary artery disease and arrhythmias.

Hope that all makes sense.

Liz

Replying to Neus E. 29/03/2022 - 13:37

Hi Liis (and everyone),

I felt that I could pop my thoughts on this subject too 🙂 Great answer Neus and I have a similar approach to these cases.

Fluids and a patient in heart failure don’t mix very well, so for me it is a big no-no too (apart from in very exceptional circumstances).

In terms of electrolyte balances, I would always focus on potassium. If around 3.0mmol/l I would generally choose oral potassium supplementation three times daily and in my experience, if they are eating, this generally normalises the potassium level. This is rarely a problem in dogs but is in cats. If less than 2.8, or not eating, then I would consider VERY cautious IV potassium supplementation as Neus discussed. Another drug you could add in would be spironolactone and this can help normalise potassium levels too. I don’t use this as a diuretic as it is generally a poor addition in heart failure, but I would use it for its potassium sparing properties and anti-aldosterone.

In terms of sodium, I never address this directly. It is usually low due to a combination of diuresis and an increase in ADH levels. It is a negative prognostic indicator in people and animals with heart failure, as is low chloride, which has had quite a bit of attention recently.

I have never placed a feeding tube for water etc, even an NG one. Generally these patients are drinking, due to diuretics. If not eating I would generally use an appetite stimulant. However, input form Kerry and Neus on this point would be valuable in terms of when to intervene with nutritional support.

I also look forward to seeing how other people handle these patients, they can be tricky.

Liz

• This reply was modified 2 years, 10 months ago by Liz Bode.

Hi Kerry,

I am just sneaking on here as I also saw this paper (CRP in pneumonia). Some useful information and another way in which CRP may benefit our patients, they use it a lot in human medicine. I don’t see that many pneumonia cases as a cardiologist but it is something that I will definitely bear in mind in future.

I also think there may be some utility in the cases of suspected myocarditis and endocarditis that we/I see. Particularly endocarditis to guide us a little about antibiotic use. Obviously, this is not founded on any scientific evidence other than they use CRP in human medicine for suspected cases of myocarditis and it is one of the recommendations in the 2013 consensus statement.

Liz 🙂

• This reply was modified 2 years, 10 months ago by Liz Bode.

Replying to Gabriela Gonzalez-Ormerod 07/12/2021 - 18:49

Hi Gaby,

Scott has asked me to answer your question on rivoroxaban vs clopidogrel in cats with HCM.

Rivoroxaban is a factor Xa inhibitor, therefore it is a true anti-coagulant as it targets the coagulation cascade but in a much more reliable way than heparin (plus it is in oral form so can give to dogs and cats at home). Clopidogrel, on the other hand, is an anti-platelet drug that binds to the P2Y12 receptor on the platelet. This blocks the effect that ADP has on the platelet (as the P2Y12 receptor is the ADP receptor), preventing platelets changing shape and so sticking to each other. It is irreversible and so binds to platelets for their lifespan.

We only have evidence for clopidogrel use in cats with HCM and FATE – this was called the FATCAT study and the abstract is here:

FATCAT study

In brief, they showed that clopidogrel increased the time to recurrence of FATE when compared to aspirin (443 vs 192days). Therefore, our preference is to use clopidogrel at the moment. It has to be remembered that this study was in a certain population though i.e. cats that had already suffered a FATE episode and we have no other evidence for other stages of disease.

We advise starting clopidogrel in any cat that has a dilated left atrium (usually a 2D left atrial size of >19mm and LA:Ao >1.7) with reduced LA function. There is currently a study underway comparing clopidogrel with rivoroxaban in cats with FATE (SUPERCAT study) but results have not been released yet and I think it will be awhile until they are available as these cats don’t tend to get referred. It might turn out that rivoroxaban is superior to clopidogrel. In people, rivoroxaban is preferred over drugs like warfarin as it has a safer profile, but obviously we don’t use warfarin in our patients.

In cats that are at high risk of FATE i.e. have had an episode, or have a thrombus/ smoke you could combine both drugs together. I tend to start with clopidogrel and if I have a cat with FATE then I might use both together.

Hope that helps,

Liz

• This reply was modified 3 years, 1 month ago by Liz Bode.