Module 2
Topic 7
Lesson 25

Is this the right signal to ablate?

Philipp Sommer
Director Clinic of Electrophysiology

What will you learn?

  • how to ablate CTI
  • what are the right signals
  • how signals should change during ablation

About this scenario

The goal of ablation for typical flutter is to create a conduction block across the cavo-tricuspid isthmus (CTI).
The procedure begins with the insertion of the ablation catheter into the right atrium, positioning it at the tricuspid valve isthmus. It's optimal to perform the linear lesion at the 6 PM position in the LAO view, or slightly more laterally to avoid risks to the AV node or nearby coronary arteries such as the circumflex or right coronary artery. Due to the variability in the thickness and length of the CTI selecting the appropriate ablation catheter is crucial. Common choices include an 8-mm tip catheter (70 Watt at 70°C) or an irrigated catheter (settings might vary based on manufacturer specifications). Ablation can be conducted either during atrial flutter or sinus rhythm, ideally starting at the tricuspid annulus. The correct placement of the catheter at the annulus is verified by observing a small atrial and a large ventricular deflection on the electrogram. If ablation triggers a premature ventricular contraction (PVC), it may indicate that the catheter has advanced too far into the right ventricle. Following successful ablation at the valve annulus, the catheter is methodically moved inferiorly towards the inferior vena cava orifice, shifting it a few millimeters every 30 seconds (if using the 8mm tip). Effective ablation at a specific atrial site is confirmed by a flattening or disappearance of the local atrial electrogram. The junction between the right atrium and the inferior vena cava (the Eustachian ridge area), presents a challenging location for catheter stability and contact. Adjusting the catheter's position slightly laterally or septally can enhance stability and ensure adequate contact.
It is crucial for the operator to maintain good contact, especially as the catheter tends to slip into the inferior vena cava from the Eustachian ridge, a common site for reconnection.
CAVE: do not overlook the "drop" to cava as prolonged ablation in this region might be lethal.
Ultimately, the ablation must achieve a complete electrical blockade between the inferior vena cava and the tricuspid annulus to prevent the continuation of atrial flutter through any small gaps in the line of block.