How to Make A Laddergram

Why Make a Laddergram?

• A laddergram shows conduction through the heart, including conduction that is concealed from the surface ECG tracing.

• A laddergram can help you test your hypothesis about an arrhythmia.

• A laddergram can help you describe your understanding of an

arrhythmia to others.

A simple laddergram has three tiers, one for the atria, one for the AV junctional area, and one for the ventricles.

A

AVJ

V

Let’s start by diagramming one cycle.

Find where the P wave begins

A

AVJ

V

& place a dot in the top of the atrial tier. This represents a sinus node pacemaker.

*

Now find where AV conduction begins, at the top of the P wave. Draw a line from the

A

AVJ

V

*

dot to the beginning of the AVJ tier at the point where AV conduction begins.

Now find where AV conduction ends, at the beginning of the QRS. Draw a line from the

A

AVJ

V

*

AVJ tier to the beginning of the ventricular tier at this point.

Now find where ventricular conduction ends, at the end of the QRS. Draw a line

A

AVJ

V

*

from the beginning of the QRS to the end of it, in the V tier.

Now, you have successfully diagrammed the conduction of a normal sinus beat.

Now Let’s Diagram an entire strip. To show a PAC, we place the dot for the site of origin a little lower in the atrial tier, to indicate a site separate from the sinus node.

A

AVJ

V

* * * * *

< 1560 ms > < 720 ms >< 1600 ms

< 1560 ms >

The line ABOVE the atrial ectopic “dot” shows us the retrograde conduction of the PAC back to the sinus node. The sinus node is reset, causing the interval between the PAC and the next sinus beat to be very close to the patient’s normal R-to-R interval.

When an ectopic impulse originates in the ventricle, it is shown like this:

A

AVJ

V

* * * * **

*

*

*

* *

The sinus P waves keep happening, even though they are concealed in the ST segment of the PVCs. They are blocked from entering the ventricles by the refractory state produced by the PVC. So, the sinus node’s rate and rhythm are undisturbed. The visual pause after the PVC is said to be “compensatory”.

Now let’s try a fun one:

A

AVJ

V

* * * ** ** *

The regular P waves marching out, with the grouped beating of the QRS complexes, identifies this rhythm as Second-degree AV Block, Type I, or Wenckebach conduction. Notice how the AVJ tier shows progressive prolonging of the PR interval, until one P wave is blocked. The P wave that fails to conduct to the ventricles has fallen into the ventricles’ absolute refractory period, and is unable to enter the ventricles.

Constructing laddergrams becomes easier with practice. You will find them very helpful as you learn more advanced concepts in arrhythmias.

This presentation is protected under a Creative Commons copyright and may be used without charge or copyright infringement for teaching purposes. Any other use, please contact Dawn.ECGGuru@gmail.com