ECG advice appreciated- where are my P waves?!

Re: ECG advice appreciated- where are my P waves?!

Holly Lee — Tue, 25 Jun 2013 20:08:10 GMT

That's really helpful, thank you very much for shedding some light on things! Holly

Re: ECG advice appreciated- where are my P waves?!

Mike Martin — Tue, 25 Jun 2013 17:25:49 GMT

[quote user="Martin Atkinson"]Is it not also that in AV block the P wave occurs normally after a QRST but in AV dissociation there is no association so the P waves are random. Also surely the apparent resynchronisation of P and QRS in AVD is purely coincidental.[/quote] In AVB, the Ps and QRSs are independant and any association is random. And yes, in AVD the resynchronisation is coincidental - it does tend to come and go so to speak - with P waves drifting before or after the QRS, usually in a 1:1 ratio.

Re: ECG advice appreciated- where are my P waves?!

Martin Atkinson — Tue, 25 Jun 2013 15:55:52 GMT

[quote user="Mike Martin"]

Yes, that is a major criteria.

AVD has 1 : 1 P to QRS whereas AVB has many Ps to QRSs

Oftentimes with AVD there is a resynchronisation of the P and QRS, before drifting apart again; whereas this does not occur with AVB

AVD the ventricular rate is typically normal to fast whereas in AVB the ventricular rate is very slow.

Hope that helps?

[/quote] Is it not also that in AV block the P wave occurs normally after a QRST but in AV dissociation there is no association so the P waves are random. Also surely the apparent resynchronisation of P and QRS in AVD is purely coincidental.

Re: ECG advice appreciated- where are my P waves?!

Mike Martin — Tue, 25 Jun 2013 15:44:36 GMT

[quote user="Holly Lee"] a grade 3 heart murmur and tricuspid valve thickening and right atrial and right ventriclar enlargement was diagnosed on a combination of xray and ultrasound[/quote] So this rules out DCM which predominantly affects the LV. Likely this dog has tricuspid valve disease. Tricuspid dysplasia is a common congential defect in this breed too.

[quote user="Holly Lee"]The dog has definitely improved in demeanour and activity since doses of the vetmedin[/quote] I see many non-cardiac cases such as dogs with respiratory disease or no significant disease which have been put on pimo and have a similar improvement.

[quote user="Holly Lee"] I appreciate this is an area where there isn't consensus but within the practice some people wish to start when there is a murmur and radiographic evidence of heart enlargement, and some only when there is evidence of congestion.[/quote] I agree it seems difficult and is a very common question. In general for CHF due to MVD only when the dog is symptomatic. When the murmur develops - pre-symptoms is too early. However there is a gray zone from when there may be symptoms that the owner is unaware of. In these case there may be cardiomegaly and maybe appropriate re-questioning of the owner might illicit a history of exercise intolerance for example - I would start then. In addition, for DCM I would follow the same guidelines, but additionally in preclinical DCM in Dobermanns (based on recent publication measurements) I would now start pimo, ie. prior to symptoms.

For the majority of dogs that present with symptoms, then get a scan to find DCM, radiographs should also be performed to screen for oedema, as this is likely to be present. It would be rare for a DCM case not to need frusemide therefore, unless it has preclinical DCM.

Re: ECG advice appreciated- where are my P waves?!

Mike Martin — Tue, 25 Jun 2013 15:34:57 GMT

Yes, that is a major criteria.

AVD has 1 : 1 P to QRS whereas AVB has many Ps to QRSs

Oftentimes with AVD there is a resynchronisation of the P and QRS, before drifting apart again; whereas this does not occur with AVB

AVD the ventricular rate is typically normal to fast whereas in AVB the ventricular rate is very slow.

Hope that helps?

Re: ECG advice appreciated- where are my P waves?!

Holly Lee — Tue, 25 Jun 2013 14:58:18 GMT

Confession time.. I'd gone too much on owner information, my assumptions and not read back far enough in the history..

In 2010 the dog had a heart scan due to having a grade 3 heart murmur and tricuspid valve thickening and right atrial and right ventriclar enlargement was diagnosed on a combination of xray and ultrasound. The vet at the time started on pimobendan and the dog has been on this ever since.

I definitely think it has neurological disease, possibly CDRM, and think this is at least part of the problem. Again I'm restricted in working this up to conclusion as the owners don't want anything major doing.

The dog has definitely improved in demeanour and activity since doses of the vetmedin have not been missed although I appreciate this could be coincidental..

As a slight aside there has been some debate within my practice as to when to start heart medication.. I appreciate this is an area where there isn't consensus but within the practice some people wish to start when there is a murmur and radiographic evidence of heart enlargement, and some only when there is evidence of congestion. I wondered what other people do..

Another case (sorry..) I saw in a labrador I diagnosed DCM on ultrasound. This dog also had an undefined arrhythmia at the time which resolved by the afternoon with a single dose of vetmedin. I have the dog on vetmedin and cardalis and the owners are resistant to physically giving more medication but I'm now wondering if I should have her on frusemide as well..

Thank you for the advise - sorry for diverging off course a little.

Re: ECG advice appreciated- where are my P waves?!

Christopher Saul — Tue, 25 Jun 2013 14:53:40 GMT

Please excuse my dim- witted question Mike ....

From a pathophysiological point of view, how does AV dissociation differ from 3rd degree AV block? Is it just that with 3rd degree block you have bradycardia whereas with dissociation you get a normocardia or tachycardia??

Re: ECG advice appreciated- where are my P waves?!

Mike Martin — Tue, 25 Jun 2013 14:35:53 GMT

Yes, it is unusual to get the two foci at the same rate. But you say on the previous day, the heart was arrhythmic - it would have nice to have seen the ECG at that time.

How was the diagnosis of DCM made? It would be unusual for a DCM case to have symptoms but no oedema. The survival in Labs with DCM is also poor, so that fact that he has had it for 'some time' is unusual. You also mention neuro deficits - what were these? Could a neuro disease be related to the weakness/lethargic? The symptoms could also be related to ventricular arrhythmias (which may be what you auscultated) and this would be common in some DCM cases. So some of the jigsaw pieces are not fitting together logically for me.

Sorry to seem to ask more questions, I always find it difficult to advise in these situation where more info is needed than available.

Re: ECG advice appreciated- where are my P waves?!

Holly Lee — Tue, 25 Jun 2013 13:28:04 GMT

Thank you for your help. Throughout the longer traces that I took at the time the P-Q interval is completely constant, which is why I hadn't suspected dissociation although it looked like a superimposition. Is it possible to get 2 foci acting at the same rate?

The dog is not showing signs of congestion which is why she's not on a diuretic - would you advise this even without signs of congestion? I advised to start cardalis but the owner declined and said she would see how the dog goes on..

Thanks again for your help, much appreciated.

Re: ECG advice appreciated- where are my P waves?!

Mike Martin — Tue, 25 Jun 2013 11:09:03 GMT

[quote user="Christopher Saul"]Given the dissociation, are the QRSs junctional in origin then?[/quote]

Yes, likely an accelerated nodal (junctional) rhythm.

Re: ECG advice appreciated- where are my P waves?!

Martin Atkinson — Tue, 25 Jun 2013 10:35:14 GMT

[quote user="Mike Martin"]In these short tracings the P wave is seen just following the QRS (and before the T). Q-P' interval is constant on these sections, which is unusual -[/quote] I humbly bow to your knowledge and experience Mike, it is obvious now but I've never seen a P wave so closely and constantly associated with and following the the QRS complex which is why I thought it was part of the S wave. As you've said a constant P-Q interval is unusual, the AV dissociation cases I've seen have all had variable P-Q intervals with accrochage.

Re: ECG advice appreciated- where are my P waves?!

Christopher Saul — Tue, 25 Jun 2013 10:26:35 GMT

Thanks Mike.

I think we were all barking up trees in the right part of the forrest but not quite the right one

Given the dissociation, are the QRSs junctional in origin then?

Re: ECG advice appreciated- where are my P waves?!

Mike Martin — Tue, 25 Jun 2013 09:06:47 GMT

AV dissociation.

In these short tracings the P wave is seen just following the QRS (and before the T). Q-P' interval is constant on these sections, which is unusual - it would be good to see more tracings to demonstrate the two independent foci (sinus + AV node). There can be occasional P capture as the P wave drifts back into position before the QRS causing a 'tripping in the rhythm' and producing irregularity on auscultation. Of course other intermittent arrhythmia may have been occurring at the time for first exam as well, not seen at the time of this ECG.

This rhythm is benign, common in Labradors, often associated with a mixed autonomic tone, eg. from being 'in the vets' - so best avoided :)

It does not explain the symptoms reported. AV dissociation would not be typical of DCM so it would be good to refer for echo. If it is DCM, then it would need more than just pimo.

Good luck, hope this helps.

Re: ECG advice appreciated- where are my P waves?!

Holly Lee — Fri, 21 Jun 2013 19:58:03 GMT

Ideally I would refer the ECG but as there's not likely to be an effective clinical treatment for either possible diagnosis, the dog's improved anyway and the owners are reluctant to spend money it's more for my learning and interest that I am keen to figure out exactly what's happening. Would certainly be good option in other circumstances though.

Am very grateful for all the input and suggestions.

Re: ECG advice appreciated- where are my P waves?!

James Laidlaw — Fri, 21 Jun 2013 13:08:54 GMT

You could always send the ECG for teleradiology or teleECG?

Idexx have a service to analyse and report back on these with a clinical history, or most cardiologists would have ability to take a look if you email them the details - not sure on costs, but cheaper than pacemaker/referral!

Re: ECG advice appreciated- where are my P waves?!

Holly Lee — Fri, 21 Jun 2013 12:53:45 GMT

Thanks for all the replies! The dog is only on vetmedin, no other meds. I did consider hyperkalaemia but not bradycardic so would be surprised. With hindsight I should have ultrasounded heart whilst ECG to look for atrial contractions but I didn't and the owner's are not keen to do too much so I doubt I'd get her back in for that unfortunately.

On lead I the first peak is merged with the QRS which I did not think would happen with a T wave, and also made me think it wasn't just an S wave which I thought it looked like in lead III.

The dog is doing much better now she's not missing doses of vetmedin, and the owner's would certainly not go for pace-making.

Re: ECG advice appreciated- where are my P waves?!

Christopher Saul — Fri, 21 Jun 2013 12:50:01 GMT

I think we need a cardiologist's opinion.... Mike? Raj?

Re: ECG advice appreciated- where are my P waves?!

Martin Atkinson — Fri, 21 Jun 2013 12:20:00 GMT

[quote user="David Mills"]Lead III gives a more obvious QRS-T morphology which correspond to the interpretation I made from lead II. From trace III I'm struggling to see what the second small waves after the T waves are if not P waves.[/quote] I'm struggling to see any any small waves after the T waves other than random baseline variation.

[quote user="David Mills"][quote user="Christopher Saul"]the first of the two small peaks after the QRS are the p waves[/quote][/quote] The peaks after the R waves are S waves, they are not usually as distinct as this but they are too regular to be P waves with accrochage, they would occur at different times.

The only other possibility IMO is that the trace is so filtered that we're missing atrial flutter/fibrillation but then if it was that the QRS would not be so regular so I'm sticking with my original interpretation.

Re: ECG advice appreciated- where are my P waves?!

David Mills — Fri, 21 Jun 2013 10:25:21 GMT

[quote user="Martin Atkinson"]

Unlike David I feel that what he interprets as P waves are T waves they are too close and too regular to be P waves and if they are, where are the T waves?. however like him I don't see evidence of atrial fibrillation/flutter either. It looks likes sino-atrial standstill with and escape rhythm to me. Atropine at 0.2mg/kg IV may help but check electrolytes as hyperkalaemia may contribute.Has it had anything other than Vetmedin ans digoxin could also cause this. If it is permanent a pacemaker may be the only solution.

[/quote]

I don't agree, though I see the reasoning.

Lead III gives a more obvious QRS-T morphology which correspond to the interpretation I made from lead II. From trace III I'm struggling to see what the second small waves after the T waves are if not P waves.

[quote user="Christopher Saul"]etrograde deplarisation of the atria; there are P waves present but these are actually secondary to the QRSs[/quote]

Retroconduction of P waves through the atria would generally produce negative P waves by definition?

[quote user="Christopher Saul"]the first of the two small peaks after the QRS are the p waves[/quote]

That would be a very quick conduction through the AV node unless there's an accessory pathway in which case you'd expect pre-excitation waveforms?

[quote user="Christopher Saul"]This is either because the SA node is not firing at all ( eg sick sinus[/quote]

I've only ever seen one SSS and it was incredibly irregular, but I know what you mean.

Also I'm measuring the QRS as 0.06s - which is a normal width - so it would need to be a high junctional tachycardia as they are not narrowed.

I'm sticking with 1st degree AV block - the regularity of association and lead III do it for me; similarly awaiting embarrassment...

Re: ECG advice appreciated- where are my P waves?!

Christopher Saul — Thu, 20 Jun 2013 16:53:58 GMT

Before I start I'm giving the caveat that I'm a medic not a cardiologist, so I await a more exert opinion from our cardiologist colleagues....

My interpretation is similar to Martin's.......

I think the QRSs represent junctional complexes and there is retrograde deplarisation of the atria; there are P waves present but these are actually secondary to the QRSs -the first of the two small peaks after the QRS are the p waves and the t waves are the second of the two.

This is either because the SA node is not firing at all ( eg sick sinus) or because the junctional rhythm is faster than that of the SA node and has taken over

i.e. a junctional tachycardia

I will now hide behind the sofa and await a passing cardiologist to shoot me down in flames

Chris

Re: ECG advice appreciated- where are my P waves?!

John Flynn — Thu, 20 Jun 2013 16:45:53 GMT

[quote user="David Mills"]looks like 1st degree AV block to me - regular association of P to QRS but with AV node delay. QRS with a closely followed T and then P wavers shortly after.[/quote]

I'm with this interpretation.

Also I expect there are VPCs around (not in this trace) if it sounded irregular with pulse deficit first time you listened (I've not seen a case jump in and out of AF before).

Re: ECG advice appreciated- where are my P waves?!

Martin Atkinson — Thu, 20 Jun 2013 16:37:31 GMT

Re: ECG advice appreciated- where are my P waves?!

David Mills — Thu, 20 Jun 2013 13:06:16 GMT

Nice traces...looks like 1st degree AV block to me - regular association of P to QRS but with AV node delay. QRS with a closely followed T and then P wavers shortly after.

Can you measure the PQ intervals? They look around 0.24s to me which is about twice as long as it should be.

With this regularity, AF very unlikely (and you have P waves, ergo impossible).

Pimobendan is a useful positive dromotrope so you're probably doing as much as you can for the AV block. Is the dog on any other meds?