That’s the spot to ablate

• how to perform activations map of EAT
• what VA linking mean
• what are the best signals for a successful ablation

Assuring that we are dealing with ectopic tachycardia and finding the right spot are essential for successful ablation. Both tasks might be quite challenging but with good preparation it should not be a problem:

• In addition to methods and techniques mentioned in Lesson 30 you can use VA linking: after entrainment of tachycardia with atrial pacing the VA interval of the return beat is the different as the VA interval of the tachycardia (it can be measured form V or His signal on one of the channels to the first A signal). Identical interval would not be expected during atrial tachycardia because atrial activation is not dependent on ventricular activation.
• During activation mapping we look for the origin of the ectopic signal. Thus, your local signal at this spot should precede all other signals. You can access this by comparing onset of the local signal to a stable reference like the first A signal from CS series. The begin of the P wave is not advisable as a reference due to low amplitude, slow slope and overlap with proceeding T wave. Putting multiple measurements in color coded map in EP system is called activation mapping. You want to see one, localized region from which a wave of conduction is spreading in all directions. If you see a large region of earliest activation or 2, 3 or more spots with earliest activation you might be mapping some tachycardia with distant origin (e.g. mapping of LA tachycardia from RA will give a large activation region on the septum) or you have incorrectly annotated the signals and second look is necessary.
• While mapping you should pay special attention to only register “true clinical” beats and not beats caused by mapping catheter. A quite robust verification is to control coupling interval from mapped beat to the previous one. In case of the clinical beat it should be always the same while beats produced by mapping catheter have different values. Also pay close attention to the sequence and characteristic of signals in CS series as it is a very good indicator of the targeted beats. If you are not sure about the accuracy of your map you can go back to the questionable points and verify your measurements.