Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common cause of palpitations in patients with hearts exhibiting no structural abnormality. After consultation with a cardiologist and an electrophysiologist, an ablation may be needed to treat the condition.
Electroanatomical mapping utilizes several catheters with sensor tips connected to mapping and navigation software. During the ablation procedure, these catheters measure conduction in electrical pathways of the heart. One catheter is placed in the carotid sinus and another in the bundle of His near the AV node. Electrodes on the catheters are then used to induce the tachycardia. This system is able to map out a three-dimensional image of the associated anatomy and allow easy revisitation of relevant recording sites identified during the study for accurate ablation.
After the ablation, the catheters in the carotid sinus and bundle of His are used to try to induce the tachycardia once again, along with administration of isoproterenol. The ablation is successful if the original induced rhythm is not reproduced.
The most common type of AVNRT is slow-fast. The fast pathway takes longer to repolarize, so the short pathway current can go up the fast pathway in a retrograde direction causing the reentry circuit that is causing the tachycardia. The slow pathway needs to be located and ablated in order to correct the slow-fast AVNRT.
The image below is an example of the three dimensional mapping. The anatomy focuses on the Triangle of Koch which is composed of the coronary sinus (CS), the tendon of Todaro, and the annulus of the tricuspid valve. The slow pathway is most commonly located towards the posterior aspect of the triangle, between the tricuspid annulus and the coronary sinus. The red dots on the map are sites that have been ablated. Once sites have been ablated, the electrode data will confirm if the pathology is corrected by demonstrating a junctional rhythm.
The image below shows the electrophysiology data from the live electrocardiogram and intracardiac electrodes. The top three, white lines are electrocardiogram data. The next two, yellow lines yellow lines represent data from the electrodes located at the bundle of His. The next five, pink lines represent data from the coronary sinus electrode. The next two, red lines are data from the ventricular electrode.
This is a picture of the electrode placement for AVNRT ablation.