ECG Pointers: When should you cardiovert atrial fibrillation?

Author: Lloyd Tannenbaum, MD (EM Attending Physician, APD, Geisinger Wyoming Valley, PA) // 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!

“Hey, you ok, kid?  You have a rough shift today?” you hear the senior resident ask the intern as he’s packing up to go home.  “You look like you’ve had better days.”

“Yeah, I had a really sick patient today and I wasn’t sure what to do.  The attending came over to help me and we got the patient to the ICU, but we didn’t really get a chance to debrief before he went home,” the intern tells her.

“Well, tell me about the case!  Maybe we can talk it though and demystify your attending’s choices a bit.”

“That would be great, thanks!  The patient was a 60-year-old male coming in with abdominal pain, fevers, and confusion. He hadn’t been feeling well for the past couple of days and then it got acutely worse last night.  He didn’t want to come to the hospital but, eventually, his wife and daughter were able to convince him to come in.  He looked unwell.  This is the ECG we got on him. I wasn’t sure what was going on; I’ve never seen an EKG like this before.”

“Let’s take a look together; this looks like a tricky one,” you hear your senior tell the intern.

Rate: 156

Rhythm: There are two rhythms here to watch.  I’ve marked up the V1 rhythm strip below, but you have atrial fibrillation (AF) and a run of non-sustained ventricular tachycardia (VT)

Axis: probably left, but hard to tell given the run of VT rudely interrupting the AF

Intervals: Both wide and narrow QRS complexes, no PR intervals

Morphology:

Final read: This ECG is tough.  It shows both AF with rapid ventricular response (AF RVR) and a run of non-sustained VT.  Let’s take a look at the rhythm strip below:

I marked this up, hopefully making it a little clearer.  The green line shows the parts where it’s AF and the blue line shows where it jumps into VT. The “F” marks a fusion beat and the “C” marks a capture beat.

“Wow, this ECG sure doesn’t look good.  And you said the patient is hypotensive, right?”

“Yeah, we should immediately perform a synchronized cardioversion on him, right?  Isn’t that what the guidelines say?  Unstable AF should get emergently cardioverted?” the intern asks.

“Well, sometimes.  It’s, unfortunately not as simple as ‘always shock patients with AF and low blood pressure.’  Let’s pull up the guidelines and talk about them quickly.  There’s one in particular I want to start with.  This is taken directly from the 2023 ACC/AHA/ACCP/HRS Guidelines for the Diagnosis and Management of AF:”

“That’s right,” the senior tells the intern, “IF the hemodynamic instability is attributable to the AF, then you should emergently cardiovert the patient.  But sometimes it isn’t.  Just because someone is in AF RVR and has hypotension doesn’t mean they always need cardioversion.  Some need resuscitation first!”

“But how do you know?  The patient is unstable, how do I know if it’s the AF causing it or something else?” he asks.

Great question!  To answer the intern’s question, there are two other papers worth reviewing briefly.  This first one by Drs. Long et al talk about how to manage AF RVR in the ED.  If I can quote their paper directly: “Of note, hemodynamic instability due to primary AF with RVR is rare and more commonly occurs in the setting of secondary AF with RVR due to another disease process (e.g., sepsis with shock) … In patients with secondary AF with RVR, treatment should focus on the disease causing the AF with RVR.  Patients with secondary AF who undergo rate or rhythm control demonstrate worse outcomes, with one study demonstrating a 40.7% adverse event rate, while patients who did not receive rate or rhythm control demonstrated a 7.1% adverse event rate.”

So, to summarize that, hemodynamic instability is possible due to AF, but it’s not common.  I always think about sepsis or some other underlying cause when a patient is hypotensive and in AF RVR.  Now let’s look at the second paper by Drs. Scheuermeyer et al (it’s the one referenced in the Long paper). It was published in 2014 in the Journal of Emergency Medicine: Emergency Department Patients With Atrial Fibrillation or Flutter and an Acute Underlying Medical Illness May Not Benefit From Attempts to Control Rate or Rhythm.

In this paper, the team looked at patients with AF and an acute medical illness.  They concluded that when you attempt rate or rhythm control with this subset of patients, there was a nearly 6-fold higher rate of adverse events compared to patients who were resuscitated first rather than had their rhythm immediately addressed.

If you take a closer look at their data, they were nice enough to stratify out who underwent “electrical rhythm control” or synchronized cardioversion.  Let’s look at their chart together:

That’s right.  Of the 15 patients emergently cardioverted, 9 of them (60%) had at least one adverse event.  Also, the authors note that only the most severe adverse event was recorded.  So, for example, if the patient had hypotension after cardioversion and got a fluid bolus, remained hypotensive, and then got pressors, it’s only charted as “hypotension requiring inotropes” not that and “hypotension requiring fluid bolus.”

Let’s go one step more.  What about all of the patients, not just the cardioverted ones? Well, 135 patients had rate (105) or rhythm (30) control attempted and 55 had an adverse event. 281 patients were NOT managed with rate or rhythm control and only 20 had an adverse event.  Taking it even one step further, 20 of the 105 patients were successfully rate controlled and only 4 of the 30 patients were successfully rhythm controlled! You could argue that this suggests the AF RVR is physiologic compensation for the underlying medical cause, rather than pathologic.

Case Wrap up:

“So what did the attending do when he came to see how you were doing?” the senior resident asks the intern.

“Well, he took over the room right away and calmed everything down.  I think the nurses knew I was in over my head.  He recognized that the patient was unstable and was in AF RVR with a run of VT.  He also looked at the other vitals, noticed he was febrile, and made him a sepsis alert.  We ran in 2L of IV fluid and started IV antibiotics.  After the fluids, he was no longer hypotensive and his heart rate was down to the 120s.  He also stopped having runs of VT.  When his pressure dipped again, we did a POCUS of his heart and IVC, saw that he could still tolerate some more fluid, and gave a second bolus.  We also started him on low dose pressors and got him admitted to the ICU,” he tells her.

“Does that make a little bit more sense now that we’ve talked?” the senior resident asks the intern.  “Instead of AF RVR, I like to think of it as AF with tachycardia.  I try and figure out why the patient is tachycardic and see if there’s an underlying issue that needs to be addressed before I just blindly start trying to fix numbers.”

“Yeah, this does make more sense.  I think I get it now. Thanks for going over the case with me!”

Summary:

• Patients in AF RVR who are unstable due to the AF should be emergently cardioverted.
• Patients with AF RVR and hypotension often have a secondary cause driving the heart rate.
• Patients with AF and an acute underlying cause may benefit significantly from resuscitation before rate or rhythm control.
  • A paper by Drs. Scheuermeyer et al found a 6 fold higher rate of adverse events in patients who were rate or rhythm controlled before resuscitation.
• Consider thinking about AF RVR as “AF with tachycardia” and ask yourself if you’d shock this patient if they were in sinus tachycardia.
  • If not, is there some underlying cause you should consider addressing which may fix their hypotension?