A 45-year-old female presents to the EP lab with complaints of palpitations and the following 12 lead ECG that was recorded in the emergency room 2 weeks prior.
12 Lead ECG:
What do you observe?
Answer:
Retrograde P Waves
Notice the retrograde P waves, appearing after the QRS. This tachycardia may be referred to as a short RP tachycardia (short distance from the QRS to the P wave).
Also, observe the narrow QRS and no delta wave is observed.
Baseline EP Study
During catheter insertion, the following rhythm was initiated.
The first EGM is the tachycardia and the second is the termination.
What are your observations?
Answer:
In the first electrogram, notice the 2:1 activation pattern. There are two atrial signals for every QRS complex. The AV/VA interval on every other complex is very short. Notice the last signal is a V on the termination image.
***IF this is the clinical tachycardia, then AVRT would be ruled out. Recall, with AVRT, there must be participation of the atrium (atria), AV node, ventricle(s), and the accessory pathway. It is not possible to have a 2:1 AVRT.
Here is the baseline recording, catheter placement, and measurements.
What is observed in the extrastimuls testing in the following electrograms? 
Answer:
AH Jump
In the first electrogram, the last S1 of the drive train is displayed and then the S2. The second electrogram has just the S2 displayed.
The second electrogram shows an AH jump, or an increase of >50 ms. This is indicative of dual AV nodal physiology. Technically, an AH jump should be performed by decrementing by 10 ms rather than the 20 ms displayed here.
Below is tachycardia initiation.
Interpret the following ventricular overdrive pacing attempt.
1. VAV – AVNRT vs. AVRT
2. VAV – Atrial Tachycardia
3. VAAV – AVNRT vs. AVRT
4. VAAV – Atrial Tachycardia
5. Not entrained
Answer:
The response is a VAV or more technically VAHV. This response is seen in AVNRT and AVRT; however, AVRT has already been ruled out with the VA block seen earlier.
If it is unclear why, please refer to the Understanding EP text for further explanation.
Where is the ablation target for this rhythm?
1. Site of AV fusion
2. Fast Pathway
3. Slow Pathway
4. Crista Terminalis
5. CTI
Answer:
Slow Pathway
The target location is at the slow pathway. The fast pathway is needed for normal conduction and should not be ablated. During RF ablation of the slow pathway, slow junctional beats are observed.
In this 3D image, an RAO and LAO view is displayed. The fast pathway is located anterior and septal and marked here with the yellow His catheter and yellow tags. The slow pathway is located more inferiorly. The colored lesions displayed are where RF energy is applied. The various colors are related to the impedance drop seen with the lesion.
Please subscribe for a weekly link to the newest blog post.
If you like this, find hundreds of electrograms to interpret in our Understanding EP workbook – included in the Understanding EP book set.
For more information: EP Essentials – Understanding EP: A Comprehensive Approach
