This is the discussion for our recent case 63 Year Old Female, CC: Neck and Arm Pain.
Let's revisit the 12 Lead ECG:
There "appears" to be a Sinus Brady rhythm at a rate of about 52 bpm, with a first degree AVB. The rhythm is regular for the first half of the ECG, then there appears to be a couple of PACs or PJCs in the second half. The axis is normal. There is ST elevation in leads II, III, and aVF and V6, with ST depression in I, aVL, V1 and V2.
As many of you correctly presumed, our patient was having an inferior STEMI, probably extending to the posterior and lateral walls. Was the RV involved? The crew did not perform right sided or posterior leads, so we do not have recorded ST elevation to confirm this. The ST elevation in III > II favors RV involvement, but there is no ST elevation in V1 (which would also favor RVI) , although the potential ST elevation in V1 may be hidden by the ST depression of the posterior involvement.
Since there was already STEMI, the crew did not run right sided or posterior leads, believing it would not alter their treatment. As the patient was normotensive, the crew elected to give NTG in addition to ASA and withold fluids.
The PCI center was almost an hour away by ground, and the community hospital only 15 minutes way. The crew elected to transport the patient to the community hospital.
Do you agree with the treatment and transport decisions?
The only follow-up was that the patient was treated with lytics for STEMI and transfered to the PCI hospital. It is not known if lytics were successful, or if it was a rescue PCI situation. Which artery was the IRA was also not confirmed.
On the subject of IRA's, it is interesting to note the ST elevation in V6. There are many who would suggest that this implies that the IRA is the circumflex artery. There is much debate about this. In Comparison of Patients With Inferior Wall Acute Myocardial Infarction With Versus Without ST-Segment Elevation in Leads V5 and V6 Iby Assali et al., the authors conclude that while ST elevation in V5 and V6 suggest a larger area of myocardium at risk, ST elevation in those leads are of no benefit in determining whether the IRA is the RCA or the LCx.
Interestingly, one element of this case that was mostly not commented on was the rhythm. Ischemia of the conduction system often accompanies inferior MI, and rhythm disturbances are common:
At first glance, it looks like sinus brady with PACs. Or does it?
Let's take another look:
First, let's take a look at lead I. If we scrutinize the QRS complex, we see a "bump" at the end of the QRS that looks strkingly similar to the morphology of the P waves. Taking our calipers to the paper, we will notice that the "bumps" march out exactly! These are in fact P waves transposed onto the end of the QRS. Rather than sinus brady, this is in fact sinus tach at a rate of about 104, with second degree type I AVB, 2:1 conduction.
Wait just a second… if it's 2:1 block, how do we know it is second degree type I? Many of us were taught that for 2:1 block you can't tell if it's type I or type II. For this, we will scrutinize V3. Starting with QRS complex #5, we see the P wave preceding it conducts with a prolonged PRI. If we again march out the P waves with our calipers, we will note that the P wave for QRS # 6 is obscured within the T wave of QRS #5. If we look closely at the onset of the T wave of QRS #6, we can see a small "blip". Marching out again, and it becomes evident that this blip (not evident in other leads) is another P wave, which is followed by a dropped QRS. Then the P wave preceding QRS #7 conducts again. So, this portion of the ECG illustrates second degree type I AVB, with 3:2 wenckebach periods. Whenever we have "grouped beating", we must first think of wenckebach and really look hard to find it. One of my goals for 2014 is to learn the art of laddergrams. It would make illustrating these concepts much easier.
A big thank you to Jason Roediger for constructing this laddergram illustrating the above:
Hope you enjoyed this case!
Thanks for reading, and as usual, I look forward to your comments!