Demonstrtion of left atrial input to the AV node in humans Circulation
- MD Gonzalez
Aim: Differentiation of Atrioventricular nodal reentry tachycardia (AVNRT) from atrioventricular orthodromic reciprocating tachycardias (AVRT) mediated by the concealed septal accessory pathway requires some electrophysiological workup. In this study we have studied the usefulness of various pacing maneuvers in differentiating the two. Results: Among the 42 patients included in our study 32 patients were finally diagnosed to have typical slow fast AVNRT and 10 patients were diagnosed to have AVRT. Sinus Cycle length, Basal AH, HV interval, tachycardia cycle length, HV interval during tachcycardia were not significantly different between the two groups. AH interval during the Tachycardia was significantly higher during AVNRT. Mean VA interval during tachycardia was significantly higher during AVRT. None of the patients with AVNRT had significant advancement of atrial activity during His refractory ventricular pacing. All patients with AVRT had significant advancement of atrial activity during his refractory ventricular pacing. During Assessment of VA (VA (Entrainment)–VA (tachycardia)), Mean VA in patients with AVNRT was 117 +/27 msec. Mean VA in patients with AVRT was 29.8+/-13 msec (P <0.0001). In three patients with AVNRT the difference was < 85 msec and none of the patient with AVRT had the difference of more than 74 msec. During assesment of Post Pacing Interval (PPI) Tachycardia cycle length (TCL), Among 28 patients with AVNRT, 24 patients (85 %) had PPI-TCL of more than 115 msec, in 4 patients the difference was less than 115 msec. Among 7 patients with AVRT, 6 patients (85 %) had PPI-TCL of less than 115 msec, in one the difference was more than 115 msec. During differential RV pacing, Among 32 patients with AVNRT, in 24 patients the Ventriculo atrial interval during basal pacing (VA base) was at least 10 msec more than the VA apex. In eight patients with AVNRT the difference was < 10 msec but more than 0 msec. Among 10 patients with AVRT, in patients VA apex was more than VA interval during base pacing by at least 10 msec. In two patients with AVRT, VA apex was less than VA base. During Parahisian pacing among the 26 patients with AVNRT 25 had the difference between stimulus to atrial interval (SA) during His non capture was at least 10 msec more than SA during His capture but in one the difference was less than 10 msec. All the patients with AVRT, difference between SA during His noncapture and His capture was less than 10 ms. Conclusion: His refractory ventricular pacing has the maximum sensitivity and specificity to differentiate slow fast AVNRT from AVRT with concealed septal bypass tracts. PPI – TCL (Post pacing interval – Tachycardia cycle length) has a lower sensitivity in diagnosing slow fast AVNRT. ∆VA (VA entrainment – VA tachycardia), a cut off of 70 ms has a better differentiating value in differentiating AVRT and AVNRT. Differential RV pacing and para hisian pacing may not be useful in differentiating slow fast AVNRT and anteroseptal bypass tracts.