Liz Bode

Replying to Christina Frigast 01/08/2025 - 13:22

Hi Christina,

No problem. I love arrhythmia and CHF management 🙂 one of my favourite areas of cardiology.

I think lack of rate control could be partly associated with poor appetite/ general malaise. You reduce your cardiac output by 20-25% in AF (no coordinated atrial contraction) and then if you add on to this the lack of rate control then cardiac output will drop again. To add insult to injury, if you have poor right sided systolic function then you will move less blood to the left side and further reduce left sided cardiac output which can also make them feel poorly. So, there are many reasons.

If her average HR over 24 hours was >125bpm on diltiazem then I would either increase the dose and evaluate response, or add in digoxin. The latter is likely to be more successful but could worsen reduced appetite etc. You also sometimes see ventricular arrhythmias on Holter and in those cases sotalol might be better. It is often a fine balance and can be trial and error to find the ‘right’ combination.

Liz

Replying to scott@vtx-cpd.com 25/07/2025 - 00:22

Hi Christina,

interesting case, and don’t be harsh on yourself, arrhythmias and ECG are tricky. I would imagine this dog had tricuspid dysplasia, given the signalment (8yo GSD) and your findings on TFAST. Sounds like you did a good work up and the main priority to to control the congestion. RCHF is rarely immediately life threatening and so you can usually get away with a more conservative approach. IV furosemide for the initial 24 hours is beneficial because they often have bowel oedema and so absorption of oral furosemide is poor. I would often use 2mg/kg 3-4 times in 24 hours for RCHF and this would usually be sufficient to get better control. I rarely perform therapeutic abdominocentesis unless there is respiratory compromise/ difficulty associated with their ascites.

In terms of your specific questions, I will try and answer in turn:

I failed to diagnose the atrial fibrillation and wonder if this is commonly seen with DCM and/or right sided heart failure?

AF is the most common arrhythmia in dogs. In one study of dogs with DCM/MMVD they found that dogs in AF were more likely to have RCHF.

https://pubmed.ncbi.nlm.nih.gov/30797441/

I think, on presentation alone, it is difficult to know it is AF. Irregular rhythms can be identified in dogs with frequent VPCs/ SVPCs/ runs of VT/ SVT and so on. The clue on ECG (and it is almost impossible to tell on an anaesthetic monitor you do need to have a paper based/ digital ECG to be sure) is an irregular rhythm with no P waves and it is often tall and narrow. The fibrillation waves can appear P wave like though at times, so it can be tricky. The key is to look for consistent looking P waves, and if you don’t really have them with an irregular rhythm then it will usually be AF. VT is wide and bizarre and will not have P waves associated with the QRS complex at all, it is usually a more regular rhythm too.

Is the aim of treatment of atrial fibrillation to control heart rate and not rhythm?

In a dog with AF and without La dilation/ or with minimal LA dilation then you could aim to rhythm control them. This would mean using a drug like amiodarone and/ or cardioverting them. I have done this successfully in a handful of dogs. However, the majoriyt of dogs with AF have significant cardiac disease and so the aim in those cases is to rate control. In a recent review by Brigite Pedro (who is doing a PhD on AF in dogs, so knows a lot) she talks about a cut off of 150bpm, so dogs with CHF and a HR of >150bpm you should control their congestion but also rate control them with diltiazem and digoxin (but only diltiazem if there is hypokalaemia/ anorexia/ GI signs as digoxin can have toxic side effects). If their HR is <150bpm then you control their congestion and once you have done this you would ideally Holter them to make sure their 24 hour average HR is <125bpm. A HR that is <125bpm over a 24 hour period means that these dogs live significantly longer.

It is hard to tell if her at times reduced appetite and lethargy is due to the arrhythmia or the azotemia but her kidney values have remained stable around 180.

I think it could be either or both! Or just because she has congestive heart failure/ gut oedema/ they can also get pancreatitis due to oedema of other organs so there are lots of reasons for the above.

I haven’t seen many cases of arrhythmia in the emergency setting so I wonder if I could have approached this case better rather than approaching it and initially managing it as congestive heart failure.

I think managing it as CHF initially was perfectly acceptable, you also referred it! In future cases you might also now be able to identify AF (and if you can get a trace you can always ask on here/ send it to us/ other referral centres) and then know that the HR in clinic i.e. > or <150bpm determines how you manage them.

Hope that is helpful!

Liz

Replying to Emma Holt 14/07/2025 - 08:53

Keep us posted!!!

Hi Emma,

Lovely to hear from you – hope you are all well.

So, in terms of sildenafil I actually do very little monitoring. I would usually monitor RRR if there was evidence of left sided heart disease – opening the pulmonary vessels could overload the LA if it is dilated/ MMVD – but I have never seen this happen, although colleagues have. I don’t monitor BP either (I check it once after starting whilst in hospital), but I do warn owners that their pet could experience hypotension and if there are any signs of that then they should let us know. I also very rarely escalate it – in my experience dogs either respond well to it or they don’t. In cases where I have increased the dose then there is often little benefit observed (but always worth a try). If I was worried about side effects then I would stop it.

Was there any ascites in this case? How severe was the PHT? I wonder if the effusion could be heart failure related and the dog might benefit from a low dose furosemide? Just a thought!

Liz

Hi Scott,

Thanks for picking this one up, I will likely cover it in our journal club in August. I tried to do a similar study using SAVSNET some years ago, but it was difficult with this data, so hats off to the RVC for managing it!

I haven’t read the paper in its entirety yet (I will save that for JC) but I think you raise valid points:

1) it doesn’t replace the advice that echo should be gold standard in an animal with a heart murmur. We echo lots of MMVD dogs that have just that, whether stage B1/ B2 or more advanced. However, some of these animals have concurrent heart disease (congenital disease for example) that might change what we do medically/ change prognosis and so on. We wouldn’t know this if we don’t perform an echo.
2) people find it tricky to determine if an animal has a grade 4/6 murmur, and mis-grading might be one issue (although even I find this tricky sometimes!), so that means a dog might have a grade 3/6 murmur mis-graded as a grade 4/6 and started on pimobendan unnecessarily. We know that dogs with a garde 3/6 murmur only 50% will have stage B2 disease, and that was the issue after EPIC lots of grade 3/6 murmurs were started on pimobendan when they don’t need it.
3) Prescribing to the incorrect individuals is costly, and it might be more cost effective over the long term to have echocardiography!
4) However, being pragmatic, if an owner is financially unable/unwilling to have echo performed then this gives us peace of mind that we aren’t necessarily doing the ‘wrong’ thing in a small breed dog with a grade 4/6 left apical systolic HM. A large breed dog/ Cocker spaniel could have DCM so it has to be used in the right selection of cases.

Hope that all makes sense!!

Liz

Replying to scott@vtx-cpd.com 28/06/2025 - 15:46

Hi both,

Most of the data we have on prolongation of QT interval with any drug is based on human studies/ side effects. This is because they are much more prone to problems associated with QT prolongation, especially as there are significant numbers of individuals with ion channelopathies whereby you really don’t want to be messing with their QT intervals! We know little about QT intervals in dogs and cats, and the data for drugs and prolongation or otherwise is scant/ non-existent. However, it would seem sensible to still avoid using drugs together with this theoretical possibility, I wouldn’t want to be the person causing sudden death by combining these drugs 😉

Liz