Liz Bode

Replying to Sarah Noponen 25/04/2023 - 19:24

Hi Scott,

The age old thyroid conundrum.

In people, there is a link between DCM phenotype and hypothyroidism. In veterinary medicine there are case reports of dogs that have DCM (some with AF) that then resolve after treatment with thyroid hormone. As you point out the only paper that looked at causation in the Doberman did not show that hypothyroidism caused DCM, but that dobermans get DCM AND hypothyroidism and that this might just be a coincidence.

That being said, in a dog with DCM it is an easy screening test to do, and occasionally you do pick up the odd hypothyroid dog. Treatment may not normalise the heart size or function but certainly having low thyroid hormone will not help the heart at all. I don’t think it is worth looking at the hearts of all hypothyroid dogs though.

In terms of NTproBNP monitoring, hypERthyroidism elevates this biomarker. Hypothyroidism can change the levels in people (some reports showed increased levels that then normalised after treatment), but there are no studies looking at NTproBNP in dogs with hypothyroidism as far as I am aware.

Liz

Hi Scott,

Sounds like an interesting case…I’d be keen to see an ECG and echo. I would assume that the echo will show MR due to MMVD given the age, breed and type of murmur. Grade 2/6 wouldn’t worry me in this case, if other things weren’t going on, but given the other signs an echo is indicated.

I’d definitely be repeating bloods here, 2 months is a long time. SSS is still a possibility, even with a HR of 75bpm, but the absence of response to theophylline possibly makes high vagal tone the cause of any bradycardia, although I would want an ECG and usually a Holter too…

So, for me, repeat bloods inc electrolytes, ECG, urine analysis, possibly a holter, echo

Liz

Hi Scott,

Great question – the relationship between the heart and thyroid hormones is fascinating in terms of physiology/ pathophysiology.

At Chestergates we currently scan all cats coming through for radioiodine treatment. I would say that the majority have some degree of hypertrophy, how much of this is primary HCM vs secondary to hyperT4 is difficult to know until you scan them again post treatment. It would be a small minority that have a dilated LA and even evidence of new onset CHF, but these are the ones that we worry about in terms of putting them through treatment as we can’t handle them for a few days once they become radioactive! Hence why we look at them all, regardless of clinical examination findings.
In general, we should investigate at least the ones with a murmur, gallop rhythm or arrhythmia. As you know, a murmur is a relatively soft finding in a cat and doesn’t mean it has heart disease. In fact some cats without a murmur can be in CHF. However, in this instance if funds allow then an echo should be advised. Another test to consider would be NT-proBNP, but hyperthyroidism can increase this without significant cardiac changes and so it isn’t as reliable in these cats.
I’d be interested to hear other people’s experiences with the above.
Liz

Hi Ornella,

My pennies worth, but I would be definitely interested to know what Neus does, she probably sees more of these cases than I do.
Firstly, it sounds like you did a brilliant job and I am not sure that there are any perfect answers here. I have never had to intubate a cat or dog with severe CHF, but that is because they are often stabilised, at least a little, before I see them. I believe your approach, starting with butorphanol IM was a good one as a ‘safe’ option in such a fragile case. I guess that if the cat was so stressed and dyspnoeic even with that then going straight to induction before a POCUS examination was performed would have been OK too. These little cats are so fragile that you’re almost doomed if you do and doomed if you don’t.
Liz

Replying to Emma Holt 05/03/2023 - 18:38

Hi Emma,
Good question! I haven’t really used it in cats with significant renal disease. According to Plumb’s there is a need to reduce the dose in cats (more so than dogs as dogs metabolise 30-40% of it) but it doesn’t go into detail. I would say that using the lower end – 50mg – would probably be OK. However, if you wanted to be completely sure then you could use an alternative. I guess as it is renally excreted that it will hang around for longer.

Liz

Hi Ornella,
Great questions!
In terms of the heart, anaemia is one of the most common ‘high-output’ states that can result in high-output failure in humans and animals. This means, as Kerry pointed out, that you have hypervolaemia and the heart has to adapt to this. It does so by eccentric dilation (think dilated chambers) and this will affect the left atrium and ventricle. An increased heart rate will also be seen. In these cases you may hear a murmur or gallop rhythm. In theory, severe anaemia can lead to pulmonary oedema which will resolve once the anaemia resolves and with management of CHF. However, this is so rare that I have never seen it. I have, however, seen plenty of cats suffer CHF through blood transfusions and intravenous fluid therapy.
Liz