Anatomy Identification
What structures are you able to identify in the following images?
What views are displayed?
Answer:
Lets work on interpretation.
The CS electrogram is displayed below. What is observed?
The first set of images displays an LAT map (Local Activation Time / timing map).
The second set is a substrate (voltage) map.
How would you interpret this result?
What ablation strategy may be utilized to terminate this tachycardia?
Answer:
The activation pattern on the coronary sinus catheter is distal (CS 1,2) to proximal (CS 9,10). This is not possible in a right atrial flutter.
On the LAT map, you can see the full 310ms AFL circuit was mapped (-150 to 150) and all of the colors are observed. The Xs on the map are at areas in which the wavefront is unable to travel due to scar. This will be more definitive on the substrate map.
In this substrate map, the low voltage areas are red and the highest voltage areas (healthiest areas) are purple.
The scale has been decreased from the traditional 0.3 to 1.5 mV or 0.1 to 0.5 mV that you typically see. Here the scale is 0.05 to 0.3 mV and that is with Multipolar substrate mapping (MP). This particular type of mapping removes far-field signal; therefore, only true local tissue signal is observed. With this very “tight” scale, it helps show is there is any channels potentially connecting the areas of healthy tissue to create a circuit. It is the “healthiest of the scar.”
Taking it one step further…
Answer:
With the use of LAT Vectors (small white arrows), we are able to observe the propagation and around the areas of dense scar as well through the small channel on the anterior wall in which the wavefront is traveling.
The second video is a ripple map, which is often helpful to observed the earliest site of breakthrough in the circuit as well as fractionation.
The physician performed and anterior line ablation from the mitral valve back to the RSPV. The atypical flutter terminated at the site of the green dot; however, a complete line of block must be created and tested for effectiveness. The remaining signal in the RSPV was also targeted after successful ablation and testing of the anterior line.
Other things of note for those with more EP experience, notice the “jump” with the propagation from septum to the anterior wall. There is a slight delay as there appears to be a clear line of block. This is likely due to an epicardial aspect of the circuit which is not accounted for in this endocardial map.
For more detailed information and examples, please refer to the Understanding EP: A Comprehensive Guide book set.
