ECG Pointers: A Dynamic Approach to Tachydysrhythmias Part 3

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 introducing part 3 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 Third Box: Wide and Irregular

This week we are going to hit Wide and Irregular tachydysrhythmias.  For this box, please keep Ventricular fibrillation (Vfib), Atrial fibrillation with aberrancy (Afib with aberrancy), and Torsades de Pointes (Torsades) in your differential.

This rhythm strip comes from a 72-year-old female presenting in cardiac arrest.  This is what you see on your first pulse check:

Figure 3a: Rhythm strip from a 72-year-old female in cardiac arrest.  Notice that the QRS complexes are wide, irregular, and low voltage.

This rhythm strip is consistent with ventricular fibrillation.  If you were to get a full 12 lead ECG on this patient, this is what it would probably look like. PLEASE keep in mind, it is rarely, if ever, necessary to get a 12 lead ECG on a patient in Vfib.  This is a diagnosis that can be made off of telemetry or a rhythm strip.  However, take a look at this ECG.  What do you notice about it?  Take a second and read it yourself before we reveal the answer.

Figure 3b: Example of what a 12 lead ECG could look like for the 72 year old female presenting in cardiac arrest

Did you read it?

Here’s what we saw:

Rate: Fast

Rhythm: Not sinus

Axis: difficult to determine, likely not helpful in this situation

Intervals: Wide QRS complexes

Morphology: No organized rhythm

Final read: Ventricular fibrillation

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

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

This next case comes from a 63-year-old female presenting with palpitations.  Take a look at her ECG:

Figure 5: ECG from a 63-year-old female with palpitations.  Again, notice that the QRS complexes are wide and the R-R intervals are irregular

Take a look at this ECG.  What do you notice about it?  Take a second and read it yourself before we reveal the answer.

Did you read it?

Here’s what we saw:

Rate: around 180 (30 QRS complexes over a 10 second EKG)

Rhythm: Irregularly irregular, consistent with atrial fibrillation

Axis: leftward axis

Intervals: wide QRS complexes

Morphology: Left bundle branch morphology is present

Final read: Atrial fibrillation with a left bundle branch block and rapid ventricular rate.  Afib with aberrancy is fancy way to say that there is abnormal conduction present and the patient’s rhythm is afib.  In this case, the abnormal conduction is a left bundle branch block.  Patients in afib with aberrancy can have other electrical problems too, such as a right bundle branch block, fascicular block, and more.

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

Figure 6: Marked up version of figure 4 to highlight the important parts

Final case for this box comes from a 16-year-old female with a known history of an eating disorder.  She is severely malnourished.  Her ECG on arrival showed normal sinus rhythm with a QTc of 598 msec.  The nurse grabs you to take a look at the repeat ECG he just obtained. Take a look at her ECG below:

Figure 7: ECG from a 16 year old female

What do you notice about it?  Take a second and read it yourself before we reveal the answer.

Did you read it?

Here’s what we saw:

Rate: Really, really fast, approaching 300

Rhythm: Irregular, definitely not sinus

Axis: Probably extreme left axis, also likely not clinically useful

Intervals: Wide QRS complexes, no obvious P waves

Morphology: Oscillating pattern of QRS complexes, extremely concerning ECG!

Final read: Torsades de Pointes

PLEASE! Check the patient for a pulse right away!

Question:  What is the difference between polymorphic ventricular tachycardia and Torsades?  Is it the oscillating morphology that points us to Torsades?

Great question!  This is a common misconception.  Many practitioners, the authors included for a while, think that every ECG that looked like figure 6 was Torsades.  It turns out that Torsades is a subset of polymorphic ventricular tachycardia and the way to diagnose it is to look at the patients ECG BEFORE they went into polymorphic VT.  IF the patient’s QTc was prolonged (>500msec), then the patient is in torsades.  If the QTc was normal, it’s polymorphic VT.

Figure 8: Marked up version of figure 6 to highlight the important parts

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 IRREGULAR category is Ventricular fibrillation (Vfib), Atrial fibrillation with aberrancy (Afib with aberrancy), and Torsades de Pointes (Torsades).
• Tips to recognize Vfib
  1. Low voltage
  2. No organized rhythm
• Tips to recognize afib with aberrancy
  1. Irregularly irregular rhythm
  2. WIDE QRS Complexes
  3. Underlying conduction abnormality, such as a right or left bundle branch block
• Tips to recognize Torsades
  1. Oscillating pattern of amplitude of the beats
  2. Prolonged QTc on ECG BEFORE the patient with into Torsades

References
– Tannenbaum L, Bridwell R, Inman B.  EKG Teaching Rounds. Springer. 2022.