Electrophysiology study and radiofrequency catheter ablation (RFCA) we
re performed in 26 patients with refractory sustained ventricular tach
ycardia (VT). After induction of VT, 12-lead electrocardiogram (ECG) w
as recorded and QRS morphology and axis of induced VT were studied to
identify the origin of VT. The precise site of VT origin were localize
d by pace mapping and activation mapping carefully. RF energy was deli
vered through a big-tip deflectable electrode catheter when the earlie
st site of endocardial activation and a high-frequency and low-amplitu
de potential of Purkinje fiber, pre ceding surface QRS by more than 25
ms, were identified and/or a pace map was obtained showing identical
QRS complexes in at least 11 of 12 ECG leads. VTs were ablated success
fully in 24 of 26 patients (success rate was 92%). For successful abla
tion, it is essential that the pace map QRS morphology in 12 leads sho
uld be identical with that in spontaneous or induced VT as far as poss
ible in performing pace map ping. Pace mapping is safe, simple and has
no unfavourable effect on hemodynamics although it takes longer time.
Activation mapping takes shorter time and has a high success rate. QR
S configuration in spontaneous VT can help to localize the site of VT
origin. Deliberate mapping at the site suggested to bo the origin of V
T by surface ECG can shorten the duration of map ping and increase the
success rate of RFCA, RFCA of VT in patients without structural heart
disease is effective, safe, and has a high success rate, so it may be
considered as an early therapy for these patients.