ECG Query - advice appreciated

RE: ECG Query - advice appreciated

Dave Dickson — Fri, 26 Apr 2019 08:58:43 GMT

Hi Alan

If no structural heart disease and no clinical signs then just watch. My money is on this dog developing sick sinus syndrome or AV block over time, but wait and see for now.

Dave

RE: ECG Query - advice appreciated

AlanH — Mon, 15 Apr 2019 20:04:21 GMT

Hi all,

So we performed a Holter last week, report came back confirming Dave's thoughts -

"The rhythm is isorrhythmic atrioventricular dissociation throughout. The P-waves can be seen to either cyclically vary in theirrelationship with the following QRS with prolonging and shortening PR interval or to 'march through' the QRS complexes cyclically. Additionally frequent supraventricular premature complexes occur and frequent dropped beats, many of which contain examples of single non-conducted P-waves consistent with atrioventricular block . The mean 24hr heart rate is 108bpm"

So im thinking the dog is haemodynamincally stable and symptom free - so I would monitor this and repeat the Holter in 3 months? Any thoughts on wether I should treat this case now or not?, does this represent an ageing change and possibly fibrosis affecting the AV node or around this area disrupting communication between the atria and ventricles ?

Thanks for any advice on this one!

RE: ECG Query - advice appreciated

AlanH — Thu, 21 Mar 2019 17:44:12 GMT

Hi all,

So we scanned him yesterday, some trivial mitral regurgitation but normal LA size LA/Ao 1.48, LV sizes all normal with good contractility so Im happy there is no structural heart disease here. My thinking is going along the lines that given normal bloods, unremarkable echo that this must be a problem in the conduction system and as Dave explains previously an AV dissociation with a junctional rhythm - I guess there tricky bit is to wether we should treat at this stage - to answer this Ive arranged a Holter so we will get that done next week and I'll update further.

Owner reports he is bright/alert and completely normal in self currently.

Any thoughts appreciated!

Alan

RE: ECG Query - advice appreciated

Liz Barton — Tue, 19 Mar 2019 21:46:01 GMT

[quote user="Dave Dickson"]Make sense?[/quote]

For sure; thanks!

I had remembered it wrong; thought it was released by the atria. All the rest I had correct in my head.

RE: ECG Query - advice appreciated

Dave Dickson — Tue, 19 Mar 2019 10:01:50 GMT

Hi Liz

There are two answers to this - the long one and the short one.

The long one: by 'classic' physiology, proBNP is a natural diuretic, released by the ventricles in response to increased wall stress (in essence, being stretched by an increased volume). This causes loss of sodium (natriuretic) which causes water loss (diuresis) and so reduces circulating volume. This then reduces LV stretch and proBNP returns to normal. Thus, in the context of left ventricular stretch due to DCM, mitral valve disease etc., proBNP is a marker of left ventricular stretch/stress.

proANP does a similar job but is released from the atria (hence the name). ANP = atrial natriuretic peptide. BNP = brain - the first place it was identified, though actually most is released from the ventricles not the brain.

The short answer is that proBNP seems to go up in response to cardiac stretch/stress. We see it go up with various feline cardiomyopathies, even where obvious LV pathology isn't identified. In dogs, most significant heart disease involves LV enlargement of some kind so proBNP (or the more stable metabolite, NT-proBNP) is used to identify significant left heart remodelling.

Make sense?

Dave

RE: ECG Query - advice appreciated

Liz Barton — Sun, 17 Mar 2019 17:23:59 GMT

[quote user="Dave Dickson"]The proBNP tells me that there is probably some left ventricular stretch/stress[/quote]

Hi Dave - I'm a bit confused by this. I thought proBNP was an indicator of atrial stretch rather than ventricular?

RE: ECG Query - advice appreciated

Dave Dickson — Sat, 16 Mar 2019 19:34:08 GMT

Hi Alan

Both the troponin and proBNP are interesting. The proBNP tells me that there is probably some left ventricular stretch/stress, which could be due to primary heart disease or it could be secondary to an arrhythmia, though most often I'd expect to see that with something like mitral valve disease. Could be secondary to bradycardia if the dog spends a lot of time bradycardia - you'd need a Holter to know more. However, I frequently see proBNP in the thousands with no obvious LV change so we really need the echo.

The normal(ish) troponin tells me there is probably no significant myocardial damage so that's good news.

Tell us what you find on echo.

Dave

RE: ECG Query - advice appreciated

AlanH — Sat, 16 Mar 2019 09:39:42 GMT

Hi Dave,

Thanks for the reply! Great to get some feedback on this - much appreciated , we ran some bloods on the day of the ECG, routine biochem and haem were unremarkable, troponin 0.12ng/ml (<0.07) and pro BNP 5,105 pmol/l (<900).

The echo has been delayed until Wednesday unfortunately but I was surprised by the raised BNP level, expecting this to be low. I will recheck for the presence of a murmur as I didn't really expect a primary dysrhythmia to lead to such an increase in BNP levels? The owner reported yesterday the dog is still clinically normal.

The troponin level although raised doesn't seem high enough to indicate myocarditis either which was on my differential list?

Will let you know what we get on echo - any thoughts on the above?

RE: ECG Query - advice appreciated

Dave Dickson — Fri, 15 Mar 2019 19:00:50 GMT

Any news on this one Alan?

RE: ECG Query - advice appreciated

Dave Dickson — Mon, 11 Mar 2019 19:41:21 GMT

Wow, cool ECG Alan.

[quote user="AlanH"]1. there is a lack of association between the P waves and the QRS waves, P waves are fairly regular through the trace but with no consistent PR interval[/quote]

Spot-on. This is AV dissociation. In essence, it's very similar to third degree block (the atria and ventricles aren't talking to each other) but there is a supraventricular (probably junctional, so around the AV node) rhythm which gives us the tall, narrow QRS.

P and QRS heights are on the top end of normal but I never use ECGs to work out if there is chamber enlargement, it's just too unreliable.

[quote user="AlanH"]2. the rhythm is a tachyarrythmia with tall, narrow complexes which I think are Supraventricular in origin[/quote]

I think the overall rhythm isn't tachy (I make the rate about 180bpm), but there are early complexes. These are slightly smaller and have a slightly different axis, probably just because they have come a little sooner. They are probably what we call "capture" beats, where the p-wave manages to get through the AV node. This is a good thing - it means it isn't a complete heart block.

[quote user="AlanH"]3. the rhythm is irregular, I thought most re-entry SVT were very regular so is this some other type of SVT? [/quote]

I don't think this is an SVT as much as AV dissociation with a junctional rhythm and some intermittent sinus conduction.

As with all ECGs, the name of the rhythm is super-interesting to geeks like me, but what matters is what we do with it!

So - I think the bloods are a good idea as a first step. Adding a thyroid and electrolytes would be a good idea. If no murmur then that makes me less worried about valve disease and cardiomyopathy is rare in Westies. Top of the list for me is Sick Sinus Syndrome - whilst this ECG isn't classic for it, this could represent one of the less common forms which is tachy-brady syndrome. Equally, it could be the start of conduction system disease around the AV node.

If the dog isn't showing signs at all then we don't need to panic. However, in an ideal world I would fit this dog with a Holter (you can order them online) and probably get an echo or some chest rads to see if we have evidence of structural heart disease.

Hope that helps

Dave

RE: ECG Query - advice appreciated

Anthony Dennison — Mon, 11 Mar 2019 17:13:21 GMT

Doesn't seem to be a link between P waves and QRS complex - almost like a wandering pacemaker. Seriously increased amplitude so that suggests an enlarged heart. Variable T wave.

Was the animal moving at all? Amplitude is quite variable as well as being increased. Electrical alternans?