VDD Single Pass Lead Pacing; Sustained Pacemaker Mediated Tachycardias Unrelated to Retrograde Atrial Activation

Abstract

Pacemaker mediated tachycardias (PMTs) are a well known complication of P synchronous pacing. Although the initiating mechanisms are several, all of them are associated with retrograde atrial activation, which is sensed by the atrial sensing channel, resulting in ventricular pacing. In 19 patients suffering from symptomatic AV conduction disturbances and normal sinus node function, a VDD pacing system connected to a single pass ventricular lead with dual chamber electrodes was implanted. The bipolar atrial electrode, floating in the right atrium, was used to detect endocardial atrial electrograms that were differentially processed within the pacemaker for optimal discrimination and filtering of undesirable signals. The widely programmable atrial sensitivity (amplitude and filtering) allowed stable P synchronized ventricular pacing in all patients, but in five of them, sustained PMTs not related to retrograde atrial activation was documented during the follow-up. The common mechanism for the onset and maintenance of these PMTs was traced to the abnormal sensing of the terminal forces of ventricular activation and/or of the T wave. The possibility of interferences between ventricular and atrial electrodes (crosstalk) was also considered. The reduction of atrial channel sensitivity represented in all cases the only effective procedure to prevent this type of PMT. In conclusion, the bet signal to noise ratio is an important endpoint to assure the proper function of a single lead VDD pacing system. Furthermore, using the differential amplifier built within the pacemaker, consideration should be given to the optimal mode of rejection of the terminal forces of the QRS and T wave.

Incessant atrioventricular dissociation due to far-field QRS oversensing and recurrent mode switch in a dual chamber pacemaker

“…Disorders of pacemaker function due to sensing of the QRS through atrial leads have long been recognized [3][4][5][6] . This phenomenon is classically described in atrial single chamber pacemakers, and leads to P wave undersensing, to inappropriate decrease in the pacing rate in AAI or AAIR mode or to pacemaker-mediated tachycardia in AAT mode [6,7] .…”

“…These problems are more rarely encountered in modern dual chamber pacemakers, because of the atrial blanking and refractory periods automatically added after each ventricular spontaneous or paced event and because of the common use of bipolar atrial leads [6] . Anecdotal cases of pacemaker mediated tachycardias have been reported when the timing of inappropriate detection is sufficiently delayed [3,4,5,7] .…”

“…Apart from pacemaker mediated tachycardias or apparent atrial undersensing [5,7] , various potential consequences of far-field QRS oversensing may be encountered in dual chamber pacemakers.…”

Hyperkalemia Induced Pacemaker Far‐Field Endless Loop Tachycardia

“…Single lead VDD pacemakers are more suseptible to FFELT because a very high atrial sensitivity is required to sense the small atrial signals registered by the floating atrial electrode. 12…”

Single Lead Atrial Synchronous Ventricular Pacing in Japanese Patients with Complete Atrioventricular Block

“…To prevent pacemaker induced complications, an appropriate patient selection is important, confirming no history of supraventricular tachycardia, atrial flutter, or atrial fibrillation. However, several reports (7,8) have demonstrated that supraventricular tachycardia sometimes develops after implantation and requires a change to VVI pacing. Brownlee at al.…”