Atrioventricular sequential pacing: differential effect on retrograde conduction related to level of impulse collision.

Abstract

Patients with DDD pacemakers who have intact retrograde conduction are known to be at risk of developing ventricular and "endless loop" tachycardia. To address this problem, a pacing protocol was designed in which V2A2 conduction was assessed in 16 patients during ventricular pacing alone (standard method) and during paced atrioventricular (AV) sequential drive (AV sequential method); the results were then compared. In eight of 16 patients who had intact retrograde conduction with both methods (group 1), the V2A2 intervals were significantly shorter (by 60 to 340 msec) with the AV sequential method. In the remaining eight patients, who demonstrated V2A2 block with the standard method, no V2A2 block occurred with the AV sequential method. In this study, two sets of AV intervals were programmed to produce collision of the two impulses (atrial and ventricular), either in the AV node or the His-Purkinje system (HPS). The site of V2A2 facilitation was related to the site of impulse collision. These results can be explained by earlier excitation by the atrial impulse (of AV node and/or HPS) during AV sequential pacing. However, in some cases it was evident that antegrade propagation of the atrial impulse was responsible for subsequent facilitation. The data suggest that assessment of retrograde conduction in candidates for DDD pacemakers can be made most accurately by the AV sequential method. Circulation 68, No. 1, 23-32, 1983. RESTORATION of normal atrioventricular (AV) synchrony in patients who need permanent pacing is not a new idea. ' However, the development of stable transvenous atrial electrodes2' has rekindled interest in AV sequential pacing. Programmable pacemakers capable of pacing and seinsing both the atrium and ventricle are now available,4 and one highly desirable feature of such pacemakers is the ability to sense the physiologic variations of atrial rate and to pace the ventricle accordingly, i.e., to accomplish atrial tracking (as in DDD, VDD, and VAT modes). The major clinical problem with these devices has been the development of pacemaker tachycardias. These are usually initiated by a premature ventricular beat (PVB), which produces a retrograde P wave. This is sensed and commits the pacemaker to stimulate the ventricle, which in turn produces another retrograde P wave, closing the "loop" and thereby initiating an "endless loop" tachycardia.5-7 A more serious arrhythmia develops when the paced ventricular beat (after a sensed retrograde P wave) falls in the vulnerable period of the initiating PVB, resulting in ventricular tachycardia.8 These complications have led some authors to suggest that intact retrograde (ventriculoatrial, VA) conduction should be considered a relative contraindication for the use of these pacemakers.9 Since intact VA conduction is found in more than 75% of patients receiving constant cycle length ventricular pacing or programmed premature ventricular stimulation,'0 many patients could be denied the use of these versatile pacemakers. Furthermore, the physiologic...

Bidirectional Ventricular Tachycardia After Radiofrequency Ablation of Idiopathic Left Ventricular Tachycardia

“…This facilitated early local recovery of the left anterior fascicle refractoriness due to summation of the two collided wavefronts or peeling back of the refractory barrier in the left anterior fascicle just distal to the level of collision. [3][4][5] Then the subsequent electric activity exited from the tachycardia traveled forward faster along left anterior fascicle due to earlier recovery of the refractoriness of the left anterior fascicle and retrogradely concealed conduction to the left posterior fascicle with collision at the route. This subsequently facilitated early local recovery of the left posterior fascicle refractoriness.…”

Recovery of Ventriculo‐Atrial Conduction after Adrenaline in Patients Implanted with Pacemakers

“…One-to-one VA conduction has been incriminated as a possible cause of the pacemaker syndrome 12 endless loop tachycardia (ELT), [1][2][3][4][5]23 and detection problems in patients with implanted cardioverter-defibrillators. 24 Most devices implanted nowadays are dual-chamber and have algorithms that prevent retrograde conductionrelated adverse events.…”

“…Retrograde ventriculo‐atrial (VA) conduction is present in up to 50–70% of patients . In normal hearts, it usually has little or no clinical manifestations.…”

“…Retrograde ventriculo-atrial (VA) conduction is present in up to 50-70% of patients. [1][2][3][4][5][6][7][8] In normal hearts, it usually has little or no clinical manifestations. However, in certain clinical settings, VA conduction can have negative hemodynamic and clinical effects.…”

Ventriculoatrial Conduction Time During Bundle Branch Reentrant Beat Initiating Orthodromic Tachycardia: A Simple and Reliable Method for Localization of Accessory Pathways

“…However, our data do not support this hypothesis inasmuch as VA 88 R values in patients with LPS and right-sided accessory pathways were considerably shorte r than V 2 A 2 • In the majority of patients with LFW accessory pathway (70 %) , VA 8 8 R was equ al to V 2 A 2 suggesting that in these cases a comparable intramyocardial conduction tim e had elapsed for both BBR and V 2 impulses to reach LFW accesso ry pathway. In the remaining seven cases with LFW accessory pathway, however, V 2 A 2 was 10-25 msec (mean 16.7 ± 6.0 msec) shorter than VA 88 R. The reason for this di sparity is not clea r, nonetheless, some expl anations may be offered as foll ows: (l) It is poss ible that compared to the BBR Jazayeri , et al l27 complex, the V 2 impu lse encountered shorter d istance or faster route to travel before reaching LFW accessory pathway; and (2) Collision of antegrade and retrograde impulse in cardi ac conduction ti ssues (i .e., AV node and His-Purkinje system) has been shown to fac ilitate the propagati on of the next impul se and hence shorten its conduction time (Shenasa , et al , 1983;Mahmud , et al , 1983 ;Mahmud , et al , 1988) . It was noted that all seven patients had rapid retrograde AV nodal conduction and the atrial activation patte rn during ventricular drive (i. e., V I impulse) predominantly occurred vi a the normal pathway.…”