Peaked T waves with normokalaemia - seen it?
Have you seen cases of peaked/spiked T waves in normokalaemic animals?
Please see the associated image HERE
This is the initial text posted as well:
"Hi folks,
Just wondered if anyone could shed some light on this ecg for me. The case was a 4yr old, MN, Dalmation dog brought in, very neuro after eating a bag of "something black" he picked up on a walk. O describes him eating this at 3.45pm, clinical signs of ataxia and fasciculations started at about 6pm and she took to MP. By 6.30pm, vocalising, unhandleable, severely hyperaesthetic.
He was transferred to us for observation (!?). Likely illicit drugs or chocolate, we thought. We have had to knock him out soon after arrival as so severely hyperaesthetic, aggressive, throwing himself around etc we could do nothing with him. Unresponsive to 20mg diazepam given at MP prior to transfer and as he was so aggressive we felt it was likely to make the situation worse if we repeated it.
pupils dilated, mm pink, crt 2 secs, unable to assess HR bit Pulse was 144, temp 103.9, nad on abdo palpation. chest normal. unable to stand, vocalising, paddling, severely hyperaesthetic
Once asleep (ga: prop +iso) the ecg showed the t waves were really spiked- K was normal and bladder intact with normal urea. Na;K ratio 40. We asked VPIS about cardiac effects of various elicit drugs but they had no data correlating to what we were seeing. HR was sustained at 120-140 with intermittent runs of 180 for about 3 hours, then gradually normalised to 100-110. the very odd VPC present for the first few hours under GA. The T waves continued the whole way through the GA.
He had 2 doses of 1g charcoal via orogastric tube whilst under GA, once at the start and one before we turned him down.
We kept the dog under GA for about 6 hours and then woke him up slowly. He made a full recovery but may have been dribbling urine a little for several hours after recovery. He ate and drank well. Discharged this morning. Dog is very aggressive normally and o said was neurologically normal. Unable to assess pulse quality or HR, PLRs or anything like that as he was agitated with me being near him and trying to attack me.
Looked up some stuff on it and saw a few cases of normal animals showing this under GA but none in the literature. Anyone have any ideas?
All the best,
Aoife"
Hi Shailen,
Thanks for this. I posted this on moodle too and Ariel posted a great response. Here it is:
So, in the absence of hyperK, how significant are any changes in the T wave?:
(From: Small Animal Cardiovascular Medicine Textbook Mark D. Kittleson )
"The T wave.
The T wave direction, amplitude, and duration depend on many variables, making changes difficult to interpret. Any changes that are noted are generally nonspecific. Consequently, T wave abnormalities commonly are not recognized and when they are present have little significant clinical meaning. The exception is in hyperkalemia, in which T wave abnormalities can be quite evident..."
if you want to know why, read on..
"The T Wave
The T wave is generated during ventricular repolarization....... However, repolarization is an independent and complicated process that does not occur as a propagated wave during normal repolarization.13 If it occurred as a propagated wave, it would inscribe a complex similar to the QRS complex. Instead the T wave is a much broader wave. In general, in the dog the epicardium repolarizes first and the endocardium last, and the apex repolarizes later than the base.14 However, multiple areas of potential difference are oriented in many directions, resulting in frequently changing relationships as repolarization is completed in dogs.15 Consequently, the T wave and its orientation to the QRS complex can change. As opposed to humans, the orientation of the T wave relative to the QRS complex is variable in dogs. In the standard limb leads, the T wave is upright approximately 50% of the time and is negative the other 50% of the time in any given lead.16"
Ariel had attached a table to this which is really useful but i cant seem to attach it to this email (sorry- am technologically challenged)
I also had another response pointing out that the QRS is also pretty small so whether this is also a factor i am not sure. Having used this machine alot, i have never seen such pronounced T waves before.
All the best,
Aoife
Thanks for sharing that. I think you are right that those T waves look spiked rather than it being related to trickery from small QRS complexes. Also there is different chat when it comes to the orientation - i.e. positive or negative - versus tall or not tall T waves. So for spiked T waves it sounds like we are left with hyperkalaemia, little clinical significance/clinical significance unknown, or myocardial ischaemia/hypoxia as considerations, with the latter being a softer conclusion. Sorted!
Not sure can help much. As far as I know, apart from with hyperkalaemia, T wave changes are considered to be pretty non-specific but may also be interpreted as suggesting myocardial ischaemia/hypoxia
It sounds like you could only get the ECG once the dog was asleep and it was not continued during/after recovery re his temperament so I guess there is a possiblity that this is normal for him - although I concede that seems unlikely.
Peaked T waves are suggested to potentially indicated myocardial infarction. There are some suggestions that although the plasma potassium concentration may be within normal limits, if you have local leakage of potassium around cell membranes due to injury, this could still caused peaked T waves; I think some people think this is why humans with myocardial infarction might have peaked T waves despite normal plasma potassium concentrations.
So I guess at the moment my thoughts would be: there was myocardial ischaemia/hypoxia, presumably related to the presumed intoxication and/or general anaesthesia; or this is normal for him; or 'dunno'.
Given your mention of some healthy animals showing this under GA, maybe the myocardial hypoxia suggestion has some weight. Also, I get the feeling that even if you are monitoring with pulse oximetry and this is within normal limits, that may not preclude the possiblity of myocardial ischaemia because oxygen delivery depends on perfusion, partial pressure of oxygen etc...
Shailen