Clinical Study Of Differential Diagnosis In Concealed Accessory Pathway Vs Atrioventricular Node Reentrant Tachycardia

Objective To determine whether the corrected difference of Postpaceing interval (PPI) between tachycardia cycle length (TCL) after entrainment of tachycardia during ventricular stimulation and para-Hisian pacing are useful, simple maneuvers in differentiating AV nodal reentrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) using a concealed accessory pathway.Methods From September 2006 to December 2007, a total of 65 patients in Second Xiangya Hospital of Central South University who underwent electrophysiological study and ablation of regular paroxysmal supraventricular tachycardia were enrolled. The patients did not show preexcitation during sinus rhythm, of which 37 patients diagnosed AVRT and the rests(28 patients) diagnosed O-AVRT.Tachycardia entrainment was attempted through trains of 5-15 right ventricular apex pacing pulses. To compare the difference of the Postpaceing interval (PPI) between tachycardia cycle length (TCL) in the two groups..The increment in AV nodal conduction time in the first PPI was subtracted from the PPI-TCL difference (namely, corrected PPI—TCL). Right ventricular pacing close to the His bundle or proximal right bundle branch was used in para-Hisian pacing. The pacing stimulus changed the capture position as the position of the ventricular pacing catheter changed subtly during respiration (or by changing pacing output). These changes in pacing capture resulted in abrupt changes in the timing of His bundle activation and the timing of ventricular activation. The presence or absence of a change in atrial activation sequence, stimulus-atrial intervals, and His bundle-atrial interval was identified.Methods Electrophysiological study demonstrated ORT in 28 patients and AVNRT in 35 patients. Transient entrainment was achieved in all but 2 patients. The mean corrected PPI-TCL difference was significantly shorter in the 28 patients with ORT (68±20 ms) than in the 35 AVNRT patients (151±16 ms; P<0.01). The presence of a corrected PPI-TCL difference <110 ms was identified in all but 1 patient with ORT, and no patients with AVNRT had such a difference. Patients with septal accessory pathways had shorter corrected PPI—TCL difference than patients with free-wall accessory pathways. Surface QRS complex showed narrow or wide among 60 patients during para-Hisian Pacing. Wide QRS complex SA interval was longer than narrow QRS complex SA interval with the same retrograde atrial activation and unchanged HA interval in the 33 AVNRT patients. While SA interval of wide or narrow QRS complex remained unchanged or changed slightly, with the same retrograde atrial activation in the 27 ORT patients.Conclusions The return cycle after tachycardia entrainment by right ventricular apex stimulation with correction for AV nodal delay is a rapid and useful maneuver for differential diagnosis of AVNRT or ORT in patients without preexcitation. The presence of a corrected PPI—TCL <110 ms may accurately identify those patients with ORT. Para-Hisian Pacing is a effective way in diagnosing O-AVRT, but it is not to be used widely in clinical practice because of difficulty in operation.