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.