الفهرس 
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Abstract
AVNRT and AVRT using a concealed accessory pathway are the most common forms of paroxysmal tachycardia and together represent around 90% of paroxysmal regular supraventricular tachycardias[42].
Currently, the most common treatment strategies
include antiarrhythmic drugs and catheter ablation[26].
Distinguishing AVNRT from ORT is often straight
forward, because an eccentric atrial activation sequence
strongly favors ORT, However distinguishing AVNRT
from ORT using a septal accessory pathway may be more
problematic because a concentric atrial activation sequence is present in both[8].
Electrophysiological study remains the gold standard
for differentiating these different types of SVT[80].However,
Noninvasive differentiation before catheter ablation may be
helpful in planning ablation procedure, decreasing
fluoroscopy time, and choosing pharmacological treatment.[81] Moreover, if responsible regions are known before EPS, the possibility of mechanical trauma on the pathways caused by the electrode catheter can be
minimized[81].
There were four different techniques in differentiating AVNRT from AVRT using concealed right accessory pathways in the electrophysiology lab. These
techniques are:
1- Atrial pre-excitation technique: VPB during
tachycardia when the His bundle is refractory.
2- PPI-TCL measurement technique: PPI measuring and
calculation of PPI-TCL after RV apex entrainment of
tachycardia.
3- Differential RV apical and basal pacing technique: RV
pacing from apex and base and measuring Ventriculoatrial
interval in each site
4- Differential entrainment of the tachycardia technique:
Entrainment of the tachycardia from RV apex and from
RV base with 10-40 ms faster than TCL and measuring
SA, VA interval and calculating the difference between
them in RV apex and base (SA-VA interval).
The study was conducted on 25 patients with narrow
QRS complex SVT presenting to the cardiology department
at Ain Shams University Hospitals to undergo
electrophysiologic study to compare a new technique which
is ”(SA-VA) after resetting of the tachycardia” to differential entrainement of the tachycardia technique regarding their sensitivity and specificity Suitable patients were subjected to thorough medical history, clinical examination.
All patients underwent electrophysiological studies
in the electrophysiology labs of Ain Shams University
Hospitals.
In the current study, measuring the SA-VA interval after resetting of the tachycardia by an extra stimulus during the His refractoriness during the tachycardia showed in AVNRT a mean of 145.76 +/- 31.53 and in OAVRT a mean of 91.52+/-12.79 with high stastical significance ( P value =0.000).
Using the ”interactive dot curve” to identify the cutoff point when using the SA-VA interval after resetting of the tachycardia in identifying the type of SVT showed that 107 msec is the cutoff point above which the SVT is expected to be AVNRT, and below which it is expected to be AVRT, which is different from 110 msec in Garcia, et
al.
According to our study, using the technique of ”(SAVA)
after resetting of the tachycardia could differentiate
AVNRT from OAVRT with overall sensitivity 100% and
specificity of 76.47%, in comparison to a specificity of
81.8% when using the technique of ”(SA-VA) apex-(SAVA)
base” ,with the same sensitivity.