What is the ratio of AV nodal block?

In atrial flutter if 3 saw tooth wave are present before every QRS complex then what is the ratio of AV nodal block ?

In atrial flutter, the characteristic ECG pattern often resembles sawtooth waves, which represent regular, organized atrial activity. The ratio of AV (atrioventricular) nodal block refers to the relationship between the atrial (flutter) rate and the ventricular (QRS) rate. It’s important to note that AV nodal block is a common occurrence in atrial flutter.

In the context of a 3:1 AV nodal block in atrial flutter, it means that for every three atrial flutter waves (sawtooth waves), only one is conducted through the AV node to produce a QRS complex. This typically results in a ventricular (QRS) rate that is one-third of the atrial (flutter) rate.

Here’s how you can calculate the ventricular rate in a 3:1 AV nodal block:

  1. Count the number of atrial flutter waves (sawtooth waves) in a specific time interval (e.g., 6 seconds).
  2. Divide the number of atrial flutter waves by 3 to calculate the ventricular rate (QRS rate).

For example, if there are 15 atrial flutter waves in a 6-second interval:

Ventricular rate (QRS rate) = 15 atrial flutter waves / 3 (3:1 AV nodal block) = 5 QRS complexes in 6 seconds

To convert this to beats per minute (bpm), multiply by 10 (since 6 seconds is 1/10th of a minute):

QRS rate = 5 QRS complexes * 10 = 50 beats per minute (bpm)

Therefore, in a 3:1 AV nodal block in atrial flutter, the ventricular rate would be approximately 50 beats per minute.