Special Case of Ventricular Rate = 150 bpm

From Dr. Vernon R. Stanley’s Animated Rhythms Course (C) 2021

Please interpret the following Rhythm strip. See bottom of post for answer.

  • a. Atrial Fibrillation
  • b. Atrial Flutter 2:1 Block
  • c. SVT 1:1 w/ Delayed Ventricular Response
  • d. SVT 1:1 w/ Ventricular Rate 150 bpm

In your quest to interpret rhythm strips, you will occasionally encounter the following:

  • Rhythm – Regular
  • Ventricular Rate = 150 bpm

When this scenario is uncovered, you should consider the following 2 examples:

Example 1: Atrial Flutter with 2:1 Block

Generally, if an irritable focus of the atria discharges at a rate of 250 to 350 bpm and takes on the shape of a sawtooth, this is called Atrial Flutter.

A common flutter rate, or “f-wave” rate, is 300 bpm.

This is often a more serious rhythm and may indicate underlying cardiac pathology.

The treatment will depend on the clinical setting and it is especially important to compare with the old cardiogram. It is clearly true that the treatment response would be different if this were a chronic pattern, as opposed to a new onset atrial flutter.

If the flutter rate = 300 bpm and the ventricular rate = 150 bpm, the practitioner must consider atrial flutter with 2:1 block. Please remember that the flutter might be appreciated in only one or two leads. Therefore, you must look for flutter waves in all twelve leads.

Example 2: SVT with rate = 150 bpm

In a typical case of SVT (Supraventricular Tachycardia), the QRS complex will be narrow unless the signal is conducted aberrantly or there is a prior widening of the QRS complex. If the P-wave is present, it is often hidden in the T-wave or QRS complex.

A typical treatment mode for SVT might include vagal maneuvers and IV Adenosine.

To compare the 2 scenarios – Atrial Flutter 2:1 Block vs SVT with a Ventricular Rate of 150 – please view the video below. For best viewing, click the gear icon and set video to 1080p and enlarge to full screen.

Clinical Comment

Please know that the recognition of atrial flutter is a daunting task at best and at worst may seem impossible to distinguish it from simply atrial tachycardia (SVT).

A clinical tool that is sometimes helpful is as follows: A vagal maneuver (valsalva, gagging, carotid massage – in absence of carotid plaque) might slow the rate and, if present, the sawtooth pattern might appear more obvious. If the rhythm is SVT, this maneuver might cause conversion to sinus rhythm.


  • Regular Rhythm: Yes
  • QRS duration: Normal
  • Rate: Tachy with QRS Rate = 170 bpm
  • Interpretation? Supraventricular Tachycardia (SVT) 1:1 vs Atrial Flutter 2:1
  • Please note a longer rhythm strip is often very helpful to decipher the underlying rhythm. More on this concept in the next blog post.

For more Rhythms animations, please see our recommended Animated Rhythms Course (6 Hrs CME)

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