ECG Pointers: A Dynamic Approach to Tachydysrhythmias Part 2

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 2 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, 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, where as 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 Second Box: Narrow and Irregular

This week we are going to cover narrow and irregular tachydysrhythmias.  For this box, please keep atrial fibrillation with rapid ventricular rate (Afib with RVR), atrial flutter (Aflutter) with variable block, and multifocal atrial tachycardia (MAT) in your differential.

This ECG comes from a 75-year-old female presenting with palpitations.  Take a look at her ECG:

Figure 3: ECG from a 75-year-old female with palpitations.  Notice that the QRS complexes are narrow and irregularly 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 150

Rhythm: Irregularly irregular, No P waves

Axis: Normal axis

Intervals: narrow QRS complexes, rest look reasonable

Morphology: Looks mostly normal

Final read: Atrial fibrillation with a rate of 150 (or Afib with RVR)

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.

WARNING!  You will often see Afib with RVR in your practice.  Please!!!! When you see these patients, turn off the part of your brain that says, “I MUST SLOW THIS DOWN IMMEDIATELY!”  Yes.  Afib with RVR needs to slow down.  The “Rapid Ventricular Rate” part of the name implies that it is going too fast.  But before you reach for that calcium channel blocker or beta blocker, PLEASE ask yourself first, WHY IS THIS PATIENT IN AFIB with RVR?  IF your patient is septic, please please please DO NOT rate control that person.  Resuscitate them first!  We promise that the rate will come down when the patient is properly resuscitated.

This next case comes from a 68-year-old male presenting with palpitations.  Take a look at his ECG:

Figure 5: ECG from a 68-year-old male with palpitations.  Again, notice that the QRS complexes are narrow 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 78

Rhythm: Atrial Flutter (more on that below)

Axis: Normal axis

Intervals: narrow QRS complexes

Morphology: sawtooth P waves (best seen in the inferior leads)

Final read: Atrial flutter with a rate of 78. Note that there is a variable number of sawtooth waves between the QRS complexes.

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 an 82-year-old female presenting with palpitations and shortness of breath.  She has a very extensive smoking history. Take a look at her ECG below:

Figure 7: ECG from an 82-year-old female with palpitations and shortness of breath.

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 120

Rhythm: Irregularly irregular. Also note the multiple different types of P waves

Axis: Leftward axis

Intervals: narrow QRS complexes

Morphology: Poor R wave progression, some nonspecific ST-T wave changes

Final read: Multifocal atrial tachycardia (MAT)

The key to this ECG is recognizing that there are 3 (or more) different morphologies of P waves.  The patient also has a long smoking history, which would support the diagnosis.  Here’s a marked-up version of the ECG to help you see what we’re seeing:

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

Figure 9: Enlarged version of 3 different P waves from Figures 6 and 7.

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 NARROW and IRREGULAR category is atrial fibrillation with rapid ventricular rate (Afib with RVR), atrial flutter (aflutter) with variable block, and multifocal atrial tachycardia (MAT).
• Tips to recognize Afib with RVR
  1. Irregularly irregular
  2. NO P waves
  3. ***LOOK FOR AN UNDERLYING CAUSE BEFORE TREATING!!***
• Tips to recognize Aflutter with variable block
  1. Sawtooth Waves
  2. Variable number of waves between QRS complexes
• Tips to recognize MAT
  1. Irregularly irregular
  2. At least 3 different P wave morphologies
  3. Often have a significant smoking history

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