Nice signal for relaxed ablation

• where you should look for ablation target
• how to find a good signal
• what is the right respond to ablation and what should you avoid

Ablating AV nodal reentrant tachycardia (AVNRT) involves a precise and well-determined energy delivery in the region of slow pathway. Remember that the goal is to modulate the slow pathway and not to ablate it completely. Here’s a step-by-step guide on how to perform AVNRT ablation:
 

• Mapping of the His bundle and fast pathway: start with mapping of the region you definitely DON’T want to damage. This will give you a good understanding of patient anatomy and no-go regions. If you use 3D-mappng system you need to make some markers for this region. If you only use fluoroscopy you can use this position as a reference and display it during the procedure to compare to your current catheter position.
• Mapping the slow pathway:  The slow pathway is typically located in the posterior-inferior region of the right atrial septum, near the tricuspid valve, and slightly anterior to the coronary sinus ostium. Practical tip is to band and retract the catheter from the His position in order to navigate to the slow pathway region.
• Intracardial signal characteristics:  Optimal signal for ablation will contain both A and V components with ration between 1:2 and 1:10. The A component needs to be at least 20-30ms later than atrial signal at the His position.
• Response to ablation: Most important confirmation about the correctness of chosen ablation region comes just after you start ablation. A good site will produce stable and slow junctional beats (CL about 500-400ms). All junctional beats need to have stable VA conduction. If you observe acceleration of junctional beats or VA (or AV) conduction problems STOP immediately.
• Duration and setting of impulse: For non-irrigated 4mm tip catheter energy delivery in a range of 30-40W should be sufficient and safe. The Impulse itself can last up to 10-20s after junctional beats disappear or slower down to 800-1000ms. However, in most cases the termination of the impulse is caused by catheter dislodgment, warning signs (conduction problem or fast junctional beats) or patient discomfort. It is very important to remember that even a shortest impulse with a good response might be sufficient for modulation of slow patient and thus curing the patient.   Therefore, it is advisable to test the inducibility after every ablation attempt.
• Post-ablation testing:  After ablation, attempt to re-induce AVNRT using the same pacing protocols. Successful ablation is confirmed by the inability to re-induce the tachycardia reentry. Note that single echo beats is an acceptable outcome where 2 echo beats pose a clinical risk of recurrent arrhythmias.