Role of SA–VA interval after resetting of the tachycardia by ventricular extra stimulus in differentiating AVNRT and OAVRT regarding sensitivity and specificity, single center study.

Abstract: Introduction: Right ventricular entrainment represents a useful tool for differentiating atrioventricular nodal re-entrant tachycardia (AVNRT) from orthodromic re-entrant tachycardia (ORT) using an accessory pathway. However, inability to entrain PSVT by pacing can be observed in some patients. Aim of study: Assessing whether the resetting response to SVT by single or double right ventricular extra-stimuli is a useful maneuver to differentiate AVNRT from OAVRT by calculating the difference between the stimulus-atrial interval during resetting of SVT and the VA interval during SVT (SA–VA). Methods: Electrophysiological study was conducted with a calculation of the SA–VA interval after resetting of the tachycardia by ventricular extra stimulus and differential entrainment from RV apex and base, then comparing the two methods regarding sensitivity and specificity in differentiating AVNRT from OAVRT conducted on 25 patients. Results: 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±SD of 91.52±12.79 with a high statistical significance, with a cutoff point of 107ms above which the SVT is expected to be AVNRT, and below which OAVRT. Using this technique could differentiate AVNRT from OAVRT with an overall sensitivity of 100% and specificity of 76.47%, in comparison to a specificity of 81.8% when using the technique of differential entrainment from RV apex and base. Conclusion: Resetting of SVT by ventricular extra-stimuli is a useful maneuver for differentiating AVNRT from ORT and is applicable even when entrainment is impossible. [Copyright &y& Elsevier]