Background:
@EN Electrophysiologic methods useful in determining the mechanism of paroxysmal supraventricular tachycardia (PSVT) accurately and easily have been continuously studied. Most studies were focused on the development of a method to differentiate
AVNRT
and AVRT using the septal atrioventricular bypass tract, since these two tachycardias are very difficult to differentiate even with electrophysiologic study (EPS). Several methods previously reported have some limitation in accuracy and/or
applicability.
@ES Objectives:
@EN The purpose of this study is to develop a new electrophysiologic parameter by evaluating the usefulness of the difference (△VACT) and ratio(VACT ratio) of VA conduction time (VACT) during right ventricular pacing at the cycle length of
supraventricular tachycardia (SVT) in determining the mechanism of SVT and localizing accessory pathways (AP) in AVRT.
@ES Methods:
@EN Total of 94 SVT patients undergoing EPS and radiofrequency (RF) catheter ablation for 85 AVNRT (17 male. 18 female; mean age 45.6±17.2 years) and 59 AVRT (36 male. 23 female: mean age 37.5±15.3 years) were included in this study. The
electrophysiologic mechanism of SVT and the location of APs in AVRT were confirmed by RF catheter ablation in all the patients. AVNRT was typical form in 34 patients and atypical (slow-slow) form in one. Among 59 APs, 19 (32.2%) APs were right
side
(12:
free wall, RFW group; 7: septum, SPT group), 40 (67.8%) APs were left side (37: free wall, LFW group; 3: septum, SPT group).
EPS was performed using the standard technique. 6F multipolar electrode catheters were positioned at the high right atrium (HRA), atrioventricular junction (HIS), right ventricular apex (RVA) in all the patients, and coronary sinus if needed. SVT
was
induced in all the patients with programmed electrical stimulation. VA conduction time (VACT) was measured from the onset of QRS complex to the onset of atrial electrogram from the HRA during SVT (VACT-SVT) and during RVA pacing at the SVT cycle
length
(VACT-RVP). △VACT was calculated by subtracting VACT-SVT from VACT-RVP and VACT ratio by dividing VACT-RVP by VACT-SVT. AVNRT and AVRT were differentiated using the previously reprted criteria and then RF catheter ablation was performed. RF was
delivered at the target site through a 7F 4 mm-tipped deflectable ablation catheter using continuous unmodulated sine wave with 350 KHz or 500 KHz generated from RF generator (RFG-3B, Radionics, Burlington. Mass or HAT 200S. Osypka, Germany).
@ES Results:
@EN The preexcitation index (PI) could be measured with a single ventricular extrastimulus in 22 (62.9%) of 35 AVNRT patients and 49 (83.1%) of 59 AVRT patients. PI was 139±31(range 90-200) in AVNRT, 30±11(range 15-40) in RFW group,
29±20(range
10-70) in SPT group, and 92±24(range 55- 160) in LFW group, showing a significiant difference between each groups, but considerable overlap (52.6% of 76) between each groups except between AVNRT and AVRT with right side AP.
△ VACT was 126±20 (range 76-168) ms in AVNRT, 17±9(range 4-35) ms in RFW group, 29±25 (5-76) ms in SPT group, 79±16 (50-110) ms in LFW group, showing a significant difference between AVNRT and 3 groups of AVRT and between 3 groups of AVRT
except
between RFW group and SPT group (p<0.01). The frequency of the patients with overlap in △VACT was lower than that in PI(52.6% vs. 24.5%, p<0.05). △VACT with a cut-off value of 50 ms differentiated the sideness (right vs. left) of APs in 58
(98.3%) of
59 AVRT patients.
VACT ratio was 3.67±1.22 (range 2.20-8.30) in AVNRT, 1.1±0.1 (range 1.03-1.29) in RFW group, 1.2±0.2(range 1.03-1.49) in SPT group, and 1.5±0.1(range 1.30-1.86) in LFW group, showing no overlap between AVNRT and AVRT. AVNRT and AVRT were
completely
differentiated with VACT ratio with a cut-off value of 2.0.
@ES Conclusion:
@EN It is concluded that the mechanism of SVT may be accurately differentiated into AVNRT or AVRT using VACT ratio with a cut-off value of 2.0 and the location of accessory pathways in VART categorized into the right or left side pathway using
△VACT
with a cut-off value of 50 ms
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