Premature beats on the ECG: where are they originating (for nurses & nursing students)?
Your nursing preceptor hands you this rhythm strip and asks you to identify which type of early beats are present. Where do you start?
Once we’ve located the EARLY complexes on this strip that’s running at 25mm/s, we want to look at the width of those early complexes.
If it’s greater than or equal to 0.12 seconds, its likely ventricular in origin.
A narrow complex QRS would indicate the impulse originated above and was conducted normally through the bifurcation of the His-purkinje system. In this case we want to determine if it’s atrial or junctional.
With premature atrial complexes, we expect to see a P wave preceding. The P wave MAY be buried in the previous T wave depending on the rate of the underlying rhythm and just how SOON the early complex is. In this case, we’re looking for disturbances in the typically smooth contour of the T wave.
Premature JUNCTIONAL complexes should have an inverted P before or after the QRS or buried within and unable to be seen. If it’s before the QRS we expect the PR interval to be short.
Of course, there are always exceptions to what we’re discussing, and this does not account for aberrant conductions… But I hope this helps!
Katz, A. M. (2011). The electrocardiogram. In F. DeStefano (Ed.), Physiology of the heart. (pp. 401-430). Lippincott, Williams, & Wilkins.