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