Dr. Smith's ECG Blog has a new case up, "
Reperfusion through collaterals associated with nitroglycerin, lateral MI with reciprocal T-wave inversion in lead III," with a pretty stark change in the initial 12-Leads. However, I have a hunch the stark change was really a change in the limb lead positions!
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVlaBEfRGpxaqdCRzWZBgEwWchbW2fonHPThNXYQJiYnAsQK27K2px1QzaNzKfIgvFmYuEgwaTFNVMWIoF8RCDpbnzVenKko81_sIl_63AYagj2jeexLr1Mgaj2Qve0QM5cr8iS2MQnF_m/s400/ecg-la-ll-reversal.jpg) |
ECG 1 and ECG 2: Limb Leads Only |
Look at leads I and II, notice how they "swap" positions between the two 12-Leads. Now look at aVL and aVF, notice how the "swap" positions too. Now take a look at lead III. It goes from inverted P's and T's with a Qr complex, to upright P's and T's with a Rs complex.
I propose that this change is due to a simple reversal of two leads. If we take a look at our friend Einthoven's Triangle (
we covered this in a previous post on the S5 Lead) we can see that this makes sense!
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4hB1O-wwo4af0mF8-ltvXCHtHUokrMRz3QZSqr4lmzxkU3MoXP7F6unapecFIO5ImLx0RqYy3WXPw4P0QW4xfLkC0TG-LECaHc3IGVzs6z8qrMSqHQ1A-d2hiy6Rg1soOEgyCAsndwlxu/s1600/Einhovens+Triangle+-+LA-LL+Swap.jpg) |
LA/LL Swap: Einthoven's Triangle is "Flipped" |
We can see that Lead I is actually looking at Lead II and Lead II is actually looking at Lead I; confirmed with ECG's 1 and 2. Lead III becomes an inverted Lead III; confirmed again in the original ECG's.
This looks like a case of an unrecognized left arm and left leg lead reversal.
What I find most interesting is if you compare every ECG except the first, it appears to be a case with subtle posteriolateral changes that may have been missed had there not been the lead reversal!