Case
A 10-year-old Japanese boy, weighting 57 kg, was referred to our hospital because of syncope or dizziness during exertion. The symptoms started at the age of 6 years and the frequency came to increase after age 9, although he refrained from hard exertion. The 12-lead electrocardiogram (ECG) during sinus rhythm and the echocardiogram did not show any abnormalities (Figure 1A ). VT was first recorded at the age of 10 (Figure 1B ). An ECG exhibited a relatively narrow QRS regular tachycardia with a heart rate of 250 bpm, a superior left axis deviation, and a right bundle branch block-type configuration. The tachycardia was not suppressed after the administration of adenosine triphosphate 10 mg, or lidocaine 50 mg. After a slowly injection of verapamil 5 mg, the tachycardia was slightly decelerated on the sustained rate alone. The treatment response represented a low sensitivity to verapamil. Because tachycardia was not controlled by oral administration of propranolol 30 mg/day, radiofrequency (RF) catheter ablation was performed under the guidance of an electroanatomical mapping system (CARTO3, Biosense-Webster, Diamond Bar, CA).
Multipolar electrode catheters were inserted via the femoral vein and were placed in the coronary sinus, at the His bundle region, and at the right ventricular apex. In addition, a linear decapolar catheter (DECANAV, Biosense-Webster, Diamond Bar, CA) was inserted to the left ventricle via retrograde aortic approach. We first mapped the Purkinje potentials along the left anterior and posterior fascicle during sinus rhythm, and tagged the sites with white circles (Figure 2A ). Then, we performed burst pacing repeatedly from several sites of the ventricles, and the VT was induced intermittently by burst pacing from the inferoseptum of the left ventricle only after the administration of high dose of isoproterenol (2 µg). Although a presystolic Purkinje potential preceding the QRS onset by 27 ms was recorded during the VT on the left posterior fascicle at the mid-ventricular septum by mapping with the linear decapolar catheter, any diastolic potentials, a common ablation target of reentrant fascicular ventricular tachycardia, could not be recorded. We performed constant pacing from several sites of the right and left ventricles with variable cycle lengths, but did not identify any constant QRS fusion, indicating that the mechanism of VT was reentry (Figure 3 ). Based on the findings, the VT was determined to occur as NRFT. We inserted a multi-spline duodecapolar catheter (PENTARAY, Biosense-Webster, Diamond Bar, CA) via a retrograde aortic to map Purkinje potentials systematically along the fascicles, and tagged the sites with blue circles. The earliest presystolic Purkinje potential, preceding the QRS onset by 34 ms, was recorded on the left posterior fascicle in the vicinity of the earliest site with the linear catheter (Figure 2 ). We placed an irrigated-tip ablation catheter (SmartTouch, Biosense-Webster, Diamond Bar, CA) at the site of the earliest presystolic Purkinje potential with the duodecapolar catheter via a transseptal approach to obtain better catheter contact, and completed RF current applications (30-50 W) at around the site (Figure 2A ). After ablation, the NRFT came to be non-inducible under high-dose isoproterenol and ventricular burst pacing. Thereafter, tachyarrhythmia has not recurred for the following 16 months without antiarrhythmic drugs and exercise restriction.