ECG Pointers: A Dynamic Approach to Tachydysrhythmias Part 4

Authors: Lloyd Tannenbaum, MD (EM Attending Physician, Geisinger Wyoming Valley, PA); Mai Saber, DO (EM Attending Physician, Hackensack University Medical Center, NJ); Rachel Bridwell, MD (EM Attending Physician, Charlotte, NC) // 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 are finishing 4 of a 4-part series tackling tachydysrhythmias.  These are very commonly encountered in the emergency department, so being able to correctly identify the rhythm is extremely important.  Let’s dive in!

When you are presented with a tachycardic ECG, we want you to focus on two major factors right away.  Ask yourself, is the QRS narrow or wide and is the R-R interval regular or irregular?  To review, for adults with the exception of toxicology, a narrow QRS complex is one that is less than 120 msec (3 little boxes) and a wide QRS complex is greater than 120 msec.  A regular R-R interval is one where the QRS complexes are marching out at a regular, predictable rate, whereas an irregular R-R interval is constantly changing.  The pictures below show some real-life examples of narrow vs wide QRS complexes and regular vs irregular R-R intervals:

Figure 1: Two rhythm strips; the top one shows a narrow complex QRS interval while the bottom one shows a wide complex QRS interval.

Figure 2: Two rhythm strips; the top one shows a regular R-R interval (blue lines are all the same) while the bottom one shows an irregular R-R interval.

Now let’s put it all together.  The following chart should be used as a starter guide for any tachydysrhythmia.  It’s not all inclusive, but it should be enough to get you a start in the right direction.  Over the course of the next few weeks, we will be breaking down each box and talking about each of the different rhythms below:

Table 1.  Differential for tachydysrhythmias.  Remember, this chart is not all encompassing, just designed to give you a start in the right direction.  Defining the terms, SVT = Supraventricular Tachycardia; Aflutter = Atrial Flutter; Sinus Tach = Sinus Tachycardia; VTach = Ventricular Tachycardia; Afib with RVR = Atrial Fibrillation with Rapid Ventricular Rate; MAT = Multifocal Atrial Tachycardia; Vfib = Ventricular Fibrillation; Torsades = Torsades de Pointes

The Fourth Box: Wide and Regular

Table 2: Differential for wide and regular tachydysrhythmias

This week we are going to hit wide and regular tachydysrhythmias.  For this box, please keep ventricular tachycardia (VTach) and supraventricular tachycardia with aberrancy (SVT with aberrancy) in your differential.

This EKG comes from a 75-year-old male presenting with palpitations.  He has a history of CHF, dilated cardiomyopathy, HTN, HLD and CAD.  Take a look:

Figure 3.

Did you read it?

Here’s what we saw:

Rate: 180 ish

Rhythm: Not sinus

Axis: Left axis

Intervals: Wide QRS complexes

Morphology: concerning

Final read: This is a regular, wide complex tachycardia concerning for ventricular tachycardia.

Here’s a marked up version of the ECG to help you see what we’re seeing:

Figure 4: Marked up version of Figure 2 to highlight important parts.

This next case comes from a 65-year-old male presenting with palpitations.  Take a look at his ECG:

Figure 5: ECG from a 65-year-old male with palpitations.  Again, notice that the QRS complexes are wide and the R-R intervals are regular

Did you read it?

Here’s what we saw:

Rate: around 150

Rhythm: Not sinus rhythm, but regular

Axis: leftward axis

Intervals: wide QRS complexes

Morphology: Left bundle branch morphology is present

Final read: This is a tough one.  It could be VTach or SVT with aberrancy.  We only know it’s SVT with aberrancy because the patient went to the EP labs with cards and we followed up on the case.

Here’s a marked up version of the ECG to help you see what we’re seeing:

Figure 6: Marked up version of Figure 2b to highlight important parts

***Please keep in mind, that from the ED point of view, monomorphic (regular) wide complex tachycardias should always be treated like VTach and let the cardiologists and electrophysiologists work out which ones are VTach versus SVT with aberrancy.***

The Brugada algorithm has been evaluated to help differentiate VT from SVT with aberrancy. However, validations of this algorithm demonstrate sensitivities approximating 80%.

For more EKG finding suggestive of VTach, please take a look at: https://www.emdocs.net/ecg-pointers-ventricular-tachycardia/.

Takeaways:

• When presented with a tachydysrhythmia, start by asking yourself if the QRS complexes are WIDE (>120 msec) or NARROW (<120 msec) and if the R-R intervals are REGULAR or IRREGULAR
• A good initial differential in the WIDE and REGULAR category is Ventricular Tachycardia (VTach) and Supraventricular Tachycardia with Aberrancy (SVT with aberrancy)
• Tips to recognize VTach
  1. Rate over 120
  2. Capture Beats and Fusion Beats
  3. AV Dissociation
  4. Josephson’s Sign
  5. Brugada’s Sign
• Tips to recognize SVT with aberrancy
  1. Diagnosis of exclusion
  2. Best left to the electrophysiologists upstairs
  3. When in doubt, treat like Vtach every time!
  4. Remember, from the ED point of view, if you are confronted with a wide complex regular tachydysrhythmia, assume VTach until proven otherwise!

For more ECG cases from Dr. Tannenbaum, please see his blog at: https://litannenbaum.substack.com/?utm_campaign=email-home&r=23qpoi

References

1. Tannenbaum L, Bridwell R, Inman B.  EKG Teaching Rounds. Springer. 2022.
2. Vereckei A. Current algorithms for the diagnosis of wide QRS complex tachycardias. Curr Cardiol Rev. 2014 Aug;10(3):262-76.
3. Isenhour JL, Craig S, Gibbs M, et al. Wide complex tachycardia: Continued evaluation of diagnostic criteria. Academic EM. 2000;7(7):769-773.