ECG Pointers: Ok, Fine. Sometimes an Ultrasound is Better than an ECG

Authors: Lloyd Tannenbaum, MD (EM Attending Physician, APD, Geisinger Wyoming Valley, PA); Christian Daniello, MD (Staff Physician, Geisinger Wyoming Valley) // Reviewer: Brit Long, MD (@long_brit)

Hello and welcome back to ECG Pointers, a series designed to make you more confident in your ECG interpretations.  This week, we feature a post from Dr. Tannenbaum’s ECG Teaching Cases, a free ECG resource. Please check it out. Without further ado, let’s look at some ECGs!

CODE BLUE, ROOM 1015 CODE BLUE, ROOM 1015!  That’s not good. Of course there’s a floor code at 2 am.  And with 28 people in the waiting room and an ED full of boarding patients.  Fantastic…

You and the code team hustle upstairs and see a patient who is clearly in distress.  He is in and out of consciousness, diaphoretic, and hypotensive.  The nurse taking care of the patient catches you up.  Mr. Jackson was admitted for atrial flutter.  He just gave him his first dose of metoprolol, as ordered.  The patient “wasn’t looking good” before the metoprolol. And now he definitely looks worse.  Here is his ECG that was obtained before the metoprolol was pushed:

Rate: Around 150-160

Rhythm: Too fast to be sinus

Axis: Left axis

Intervals: Narrow QRS

Morphology: Looks like saw tooth P waves, best seen in the inferior leads.  There’s also low voltage globally in this ECG.  And take a look at V5 running across the bottom of the strip.  The voltage changes every other beat.

Final Read: This ECG looks like flutter.  It also shows signs of low voltage and electrical alternans!

Electrical alternans sounds like something we read about in textbooks that isn’t real.  Just like unicorns and that consultant you call at 2 am who sincerely thanks you for that interesting consult.

Due to the low voltage and electrical alternans, you decide to throw a probe on this patient’s chest, and here is what you see:

Well.  I am not super great with an ultrasound, but even I can see the big black “C” shape surrounding the heart and know enough to be concerned for a large pericardial effusion potentially causing tamponade.  For ultrasound things, I turn to my friend, Dr. Joe Kim.  He’s an Ultrasound guru.  The things this man can do with a probe and some gel will blow your mind.  Joe sent me this video on what tamponade will look like on a POCUS Echo:

But what are we seeing here?

This video shows a parasternal long axis view of the heart.  You see at the top of the screen, the pericardial effusion with the right ventricle (RV) bouncing around.  The big tipoff that this is tamponade is that the right ventricle collapses at the end of diastole.  Often referred to as “RV end diastolic collapse.”  This is pathognomonic for tamponade. The way to know that you’re seeing RV collapse at the end of diastole is that the mitral valve is open but the RV is completely collapsed.  Take a look at this still screen shot from the video below showing you the RV end diastolic collapse:

Labels: PCE = Pericardial Effusion, RV = Right Ventricle, LA = Left Atrium, MV = Mitral Valve, LV = Left Ventricle, DTA = Descending Thoracic Aorta

 This still image comes from roughly around second 3 of Joe’s video.  What we’re seeing is a large pericardial effusion (PCE) causing end diastolic RV collapse.  Notice that the mitral valve (MV) is open in this shot.  This image is a slam dunk for tamponade.  This human needs immediate intervention!

Side note, thank you to Dr. Jailyn Avila for adding this bonus tip: If you’re not sure, based on your US, if the patient is in tamponade or not, take a quick peek at the inferior vena cava (IVC). If the IVC is plethoric (>20 mm in an adult) or you lose respiratory variation in the IVC, these are also signs of tamponade!

But what do we do with tamponade?  We have a hemodynamically unstable patient with a large effusion concerning for tamponade.  I know, I don’t want to do it either.  But it’s time to talk about a pericardiocentesis.  Talk about a procedure we don’t do every day.  Let’s quickly review how to perform one:

Classically, pericardiocentesis was taught to be performed blindly.  The patient would be lying there in extremis while you laid him flat (bad), took a very long needle (Scary), and, using a subxiphoid approach, directed at the left shoulder, blindly tried to access the pericardial space to drain the effusion while trying your best not to stab the heart (Terrifying).  As would be expected, this carries a high complication rate.  Just like central lines, ultrasound has made this process (slightly) easier and a little less terrifying.

There are two ultrasound guided methods you can use to access the pericardial space.  US assisted and US guided.  In the US assisted method, the physician will take the US and map out a course to the effusion.  This will help to know how to position your needle and how deep to insert, hoping to minimize complications, like stabbing the heart.  This method leads to less complications than a blind approach, but it’s not much better.  US guided seems (to me) to be the safest approach.  In the US guided approach, this seems very similar to a combination of paracentesis and central line placement.  Using the US, you find the largest pocket of fluid and then visualize the needle entering the pericardial space.  As long as you keep your needle tip in view the entire time, you should be able to minimize complications.  Take a look at this article from Alerhand et al.  It’s an excellent review of pericardial tamponade published in AJEM in 2022 which has a ton of pictures of tamponade and walks you through how to drain effusions using ultrasound.  Many excellent, high-quality images.

While the code team is thrilled with you ultrasounding the crashing patient, curbside consulting Joe Kim and hoping that the metoprolol would quickly wear off and bring up the patient’s blood pressure, they need some action from you.  “Doc, what’s the plan?” Your nurse asks you.  Here goes nothing, you think.  You ask for the pericardiocentesis kit, grab the ultrasound and get to work.

You’re able to visualize a large pocket, watch the needle enter the pericardial space and pull off some fluid!  Success! (Sidebar: for a great Youtube video on performing a pericardiocentesis with a ton of great US clips, take a look at Dr. Avila’s video (Link: https://www.youtube.com/watch?v=G3PsxQhZErY).  It’s an amazing walkthrough)

Ok, you drained the effusion.  You’re not sure who was shaking more during the procedure, you or the patient, but at the end of the day, you got enough fluid off of this patient’s heart that he’s feeling much better.  He’s breathing better, his blood pressure has come up, and you look like a rockstar.  You call your cardiothoracic surgery colleagues who thank you for this interesting consult at 2 am and are on their way in to perform a pericardial window.

Before you head back down to the ER where you have 37 patiently waiting patients, let’s talk about what I want to talk about, the ECG!  Too much too much ultrasound.  While Joe gets all cleaned up from the Ultrasound goo, let’s touch on ECG findings of tamponade before wrapping up.

How good is an ECG at warning us about tamponade?  Well, this makes me sad to admit, but it’s actually pretty bad.  I know, I know. Read through the tears.  Take a look at this table below, reprinted from Alerhand et al’s excellent review of pericardial tamponade (this is the paper I linked to above):

It’s ok.  I don’t blame you if you find this depressing too.  Electrical alternans, is present in less than 20% of cases of tamponade.  The most common finding?  Tachycardia.  Not very specific unfortunately.  I think a good rule of thumb to consider is: if an ECG has low voltage, take 30 seconds and put an ultrasound probe on the patient’s chest.  It doesn’t take very long, and a pericardial effusion is easy to see on ultrasound.  Heck, even I can do it, and I’m one of the worst ultrasounders out there. Ok, enough science, hustle back to the ED and go see those patients!

Let’s do a quick recap:

• Electrical alternans is a cool finding, but it’s not seen very often in patients with a pericardial effusion.
• If a patient has a low voltage ECG, consider taking a quick peek with the US to check for a pericardial effusion.
  • It’s easy and doesn’t take a long time
• On ultrasound, tamponade can be seen by end diastolic RV collapse.
  • You can tell because the mitral valve will be open and the right ventricle will be collapsed.
• If your patient is truly unstable and needs a pericardiocentesis, consider using an US guided approach, as it has a lower complication rate than a blind approach.
• Fine. There are some (rare) instances when I’d rather have an US machine than an ECG machine.