This is a challenging one! Take your time and try to determine as much about it as you can.
I am going to try to get some regular ECG’s back up for you guys but bare with me! The format has changed. Now rather than waiting for the following weeks ECG to show up for the answer, it will just be in the post. You will have to click “continue reading” though just to force you to spend some time thinking about it before you decide on what it is.
I hope you picked this up! If not I am sure you will catch it next time. So first of all lets get on the same page as to what Atrial Trigeminy is. In plain terms, it is a premature atrial beat following two regular beats.
When we assess anything along the atrium we want to use the right tools for the job. So that being said our main focus needs to be on V1 and V2 as they are sitting right on the atria. The two together should be used to try and see those fancy little P waves.
What are we looking for in terms of a P wave you may ask? Well firstly their interval. The last beat in each triplet arrives early! Perfect! That is the definition of premature in a nutshell.
How can we confirm if it is coming from the atrium rather than the SA node, AV junction or the ventricles? The form of our P wave will tell us the story. Remember the tell tale signs of the major foci! The AV junction typically has a negative deflection due to the retrograde conduction. The ventricles do not conduct the P wave (this doesn’t mean their wasn’t an atrial contraction). So this leaves everything above the ventricle. If the depolarization is coming down from the atrium into the junction we would expect a positive deflection of the P wave. Typical atrial conduction’s tend to be more pointed than a regular SA node P wave. We can see this in the second and third cycle. If they all have varying peaks, chances are you are looking at multiple atrial focuses which are harder to assess due to the lack of regularity and the overall irritability of the foci. For now though, be happy with the peaked P wave.
I can go into the prolonged interval from the PAC to the next normal beat, however I will let the source do the talking for me!
Source: ECG Blog
Before I go, I want you to take a look at the limb leads which accompany this printout. I wanted to isolate you to the precardial leads for this as this would likely send you up the wrong path. It would be easy to say there is a presence of a bundle branch block as seen in the majority of the leads. However remember! The best leads to assess the conduction of the bundle branches are along V1-V6. The exception to this rule is assessing your hemi blocks, but that is a more advanced topic.
If you think what you saw in lead I-AVF may have been ST elevation. Remember, it isn’t if the S isnt connected to the T. For each QRS there is a clear distinction of a P and a T.