ECG thoughts..

Re: ECG thoughts..

David Mills — Wed, 27 Mar 2013 13:04:41 GMT

[quote user="Holly Lee"]

Worth a echo to look for underlying structural disease?

[/quote]

Possibly. It's normally fibrosis, though occasionally can be inflammatory, neoplastic etc but may not see anything. Can see with HCM so it may be worth staging this. If its been present for a while (>3 weeks) you may well see a strikingly dilated heart from chronic volume overload.

[quote user="Holly Lee"]

Is the ventricular rate quite rapid for an AV block? Or is this just because I'm more used to dogs than cats?

[/quote]

It looks junctional to me, which usually have a rate of 100-140 in cats. Ventricular would be lower, less than 100bpm.

Dogs normally junctional 50-70, ventricular <50.

Re: ECG thoughts..

Holly Lee — Wed, 27 Mar 2013 12:28:14 GMT

That;s great, thanks very much for your inputs. Worth a echo to look for underlying structural disease?

I did advise against doing the dental at least until I'd figured out what might be occuring.

Is the ventricular rate quite rapid for an AV block? Or is this just because I'm more used to dogs than cats?

Thanks again,

Holly

Re: ECG thoughts..

David Mills — Wed, 27 Mar 2013 10:58:05 GMT

I agree with Mr Flynn - this is 3rd degree AVB; I think they could be T waves from a junctional escape rhythm. Could be an element of RBBB.

However, it still also could be an atrial bradycardia with escapes but the only thing against that is the two P waves preceding QRS at the end of the trace (last two blue arrows) where there is no consistent relationship suggesting P waves are happening in the background.

Some P waves appear buried within the junctional escape rhythm and the T waves. The T wave sizes regularly alternate - on the diagram below the pink arrows show the taller ones with buried P waves. There are blurred upstrokes of the QRS apparently without P waves (green arrows). The blue arrows later in the trace show where I think the P waves are occurring. Yellow circle is a VPC. After this you can see delineation of the P and QRS (blue arrows sequentially).

This cat would be a high risk GA without pacing as there is a risk of losing the escape rhythm and cardiac arrest. A recent case report, however, described how a CRI of dopamine and dobutamine in a dog with 3AVB increased HR (increased escape rhythm rate) during GA to ensure stability, with dobutamine being the key factor (dopamine alone no effect) - let me know if you want a copy. Suppose it depends how badly it needs a dental.

Many cats IME live quite happily with 3AVB. People try anticholinergics but they are rarely vagally mediated and side effects aren't great. Pimobendan is probably your best shout for home meds as it has positive dromotropic effects which have raise HR.

Re: ECG thoughts..

John Flynn — Wed, 27 Mar 2013 08:10:14 GMT

Hi Holly,

I don't think those p-waves are related to the complexes coming after them. look at the the complexes below "26 Mar"just after the complex - first seems to have a p just before it and next has more of a gap. I think the p-waves are doing their own thing.

Also the complexes all look ventricular to me - I don't think those are t waves, just all big ventricular complexes.#

I'm not totally sure what conclusions I'd draw from that other than I wouldn't GA for a dental in a hurry. Possibly a third-degree AV node block, or some form of myocardial disease (or both)?

Re: ECG thoughts..

Holly Lee — Wed, 27 Mar 2013 07:43:28 GMT

Possibly not the best scan in the world. I did have some on 50mm/s but those bits have got a lot of interference on the trace.

Also when I finished measuring confirmed R waves much lower amplitude than would expect and over large T waves.

It is an old cat, it was due to have a dental but I don't think that it had any other specific problems (I was ECGing for a colleague and not at work right now so not got full details with me). Biochemistry & electrolytes were mostly normal, just a marginally low potassium (3.2, our ref range starts at 3.5)

Re: ECG thoughts..

David Mills — Tue, 26 Mar 2013 23:44:36 GMT

Is there any chance of posting the trace? Despite your great description, but with ECGs a picture does tell a thousand words...

But.

Initial thoughts. This could be a sinus bradycardia with junctional escape rhythm. It could be 3rd degree AV block with P waves buried in alternate QRS (made be very subtle changes in shape) and a false appearance of conducted P waves every other QRS, but I can't imagine how this would fit as P (and escape rhythms) normally constant intervals though upto 10% variation does occur. QRS from junctional escape rhythms can look just like normal QRS if they are started from high in the conduction system.

If sinus bradycardia, increased vagal tone, intrinsic SA node disease, metabolic abns and autonomic NS disorders need to be considered.

Old cat? Any other signs?