Discussion
PJRT is an uncommon but important causes of refractory SVT in infants and children.5,6 These accessory pathway typically have only retrograde conduction properties and are slow and decremental. The pathway characteristics are similar to AV nodal tissue and therefore the circuit has two decrementally conducing limbs making for stable reentrant SVT at varying cycle lengths.2-4
Medical management can be difficult and poor rhythm and or rate control can lead to cardiac decompensation and tachycardia induced cardiomyopathy. These pathways are most commonly located in the right septal area, more commonly near the posterior septum but mid or anterior septal locations have also been described. The right posteroseptal pathways may be close to the ostium of the CS and may be within the proximal CS but locations have been described in almost any position along the AV groove.3,5,6 However epicardial connections distant from the mitral and tricuspid valve annulus within a diverticulum of the CS are unusual and to the best of our knowledge an ablation in this location has not been previously described in an infant.
We opted to perform an aortic root shot in our patient prior to RF application as ablation of accessory pathways from within the CS may lead to damage to nearby coronary arteries (CAs) and their branches. Specifically the posterolateral (inferolateral) ventricular branch of the right coronary artery and the left circumflex artery run inferiorly and in close proximity to the CS. Use of radiofrequency catheter ablation within the CS has been reported to cause ischemia and infarction due to stenosis or complete occlusion. Symptoms may be acute and catastrophic or present several weeks later.7
Other complications described with RF lesions within the CS include cardiac tamponade, AV block, and pericarditis and our infant went home on a 30 day event recorder to monitor for late onset heart block.8
In our patient we choose to deliver a low power RF burn at 7 W, to avoid perforation of this tiny CS branch. Kusano et al have described low power 10W lesions in the coronary sinus achieving temperatures of 60 degrees.8