What is it and how to measure ERP

Acknowledgement

Daniel Scherr

Chair of National Society

What will you learn?

The most common type of refractoriness measured in clinical practice is effective refractory period (ERP). You can determine refractoriness of myocardial tissue (atrium, ventricle) and of a conducting structure (AV node) during EP testing. EPR is the longest coupling interval that fails to capture.
ATRIUM: when you perform S1S2 from CS 9-10 electrode, you will observe that at a certain S2 (i.e. 200 or 220 ms) atrium is captured with no conduction to the AV node, so you can see the A potential with no H and V signals. This S2 value is the AV node ERP (AVNERP). When you continue the S1S2 stimulation, you may notice that after S2 (i.e. 180 ms) there is no atrial capture. You reached a point at which atrial tissue itself is refractory and is no longer captured. During your EP study, you will notice S2 stimulation spike with no A signal. The S2 value is the atrial ERP (AERP).
VENTRICLE: let's stimulate from the RVA electrode to determine the retrograde ERP of the AV node. You perform S1S2 from RVA. At a certain point you will notice that after S2 there is a V signal with no A signal - this is retrograde AVNERP. Afterwards, when you continue S1S2 stimulation, there will be a point there after S2 stimulus there is no V capture - you reached VERP.