EP study:
The EP study was performed under general anesthesia on inotropic
support. The infant was in incessant SVT in the EP lab. A 3 catheter
study was performed with access through the right and left femoral
veins. 3 D electroanatomical mapping was performed with the EnSite
Precision™ mapping system (Abbott Medical, Inc, St Paul, MN). A 4 Fr
decapolar (Inquiry™, Abott Medical, Inc) was placed in the CS and a 4 Fr
quadripolar catheter (JSN TM, Abbott Medical, Inc) was
placed in the right ventricular apex. Mapping was performed with a 5 Fr
Marinr small curve catheter (Medtronic, Inc., Minneapolis, MN, USA).
Atrial extrastimuli resulted in transient interruption followed by
resumption after two to three sinus beats. His bundle‐refractory PVCs
during tachycardia delayed atrial activation. Entrainment during SVT was
performed with pacing in the RV apex and the atrial activation sequence
during pacing was identical to the tachycardia. It was clear early on in
the case that the pathway location was close to the CS dipoles 7.8
within the CS. Detailed mapping of the right septum and postero-septal
space was performed and the Mariner was inserted into the CS alongside
the decapolar catheter. Earliest atrial activation during SVT was noted
in a diverticulum off the os of the CS (Figure 1). An aortic root shot
was performed through a 4 Fr pigtail catheter in the RFA to delineate
coronary anatomy. The catheter tip was distinct from the main coronary
arteries and branches. Current delivery with a low power 7 Watt lesion
resulted in an immediate temperature increase to 50 degrees Celsius,
impedance of 115 ohms and cessation of the SVT within 1.3 seconds
(Figure 2). This was evidenced by a change in heart rate and CS
activation pattern. The lesion was applied for a full 40 seconds. No
insurance burns were applied. A full EP study was then performed in
sinus rhythm and was normal. Repeated electrical stimulation was
performed with atrial and ventricular single and doubles at coupling
intervals down to 180 msec on and off Isoproterenol and during the
washout phase of the drug with no evidence of SVT. 60 minutes post
ablation the catheter were removed.
Post ablation course: The patient was transferred back to the ICU
with continuous telemetry monitoring. Milrinone was stopped 12 hours
post ablation and an echocardiogram 48 hours later showed an improvement
in EF to 45%. The patient continued to be in sinus rhythm three days
later and was discharged home on a home telemetry monitor. Six month
later the patient is doing very well with completely recovered cardiac
function off of medications.