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.