Evaluation of the Atrial Evoked Response for Capture Detection with High‐Polarization Leads

Abstract

AutoCapture based on the evoked response can be confounded by electrode polarization. In this study, polarization was measured in human subjects who had chronic atrial leads. The aim of the study was to determine whether electrode polarization can be measured using a time integral atrial evoked-response integral (AERI) of the negative portion of the atrial paced ER evoked-response signal and to determine whether high-polarization atrial leads unsuitable for AutoCapture can be identified a priori. Atrial intracardiac-electrogram (IEGM) signals from 39 patients with implanted pacemakers were recorded and analyzed. The signals were recorded during conventional atrial-threshold searches. A total of 221 atrial-capture thresholds were recorded, ranging from 0.25 to 2.75 V with a mean of 0.79 V. Each evoked response was evaluated using the AERI in a 36 ms window following the 0.4 ms atrial stimulus. The polarization was estimated as a linear function of stimulus voltage using the evoked-response signal integral of captured beats identified on the IEGM. The 221 threshold-search datasets were obtained using leads with eight different electrode materials. Polarization could be measured using AERI as a function of stimulus voltage. Furthermore, this polarization measure can be used to identify high-polarization leads, which are ill suited for the atrial AutoCapture algorithm.

Atrial Threshold Variability: Implications for Automatic Atrial Stimulation Algorithms

“…All newly implanted leads were steroid‐eluting. Median follow‐up was 12 months 6–18 ; no lead dislodgement was observed. Clinical characteristics of the patients are reported in Table I.…”

“…Indeed, the ACM algorithm is not based on the detection of an AER, which could prove useful in pacingdependent patients and in this latter challenging scenario, but is still under evaluation. [8][9][10]14 Nonetheless, the ACM success rate is high if the number of threshold measurements is increased: our observations during long-term followup suggest that atrial output could be managed by the pacemaker itself, thereby enhancing patient safety in the event of a threshold increase, and saving time-consuming manual threshold measurements. Moreover, the detailed history of the atrial threshold may be used as a clinical indicator of underlying heart disease or atrial pathology, or of the effect of antiarrhythmic drugs.…”

“…It appears from our data that threshold measurement could be challenging in patients with%Ap > 40% and first‐degree AVB (these clinical features imply an ACR success rate ≤ 50%, and a 27% success rate for AVC). Indeed, the ACM algorithm is not based on the detection of an AER, which could prove useful in pacing‐dependent patients and in this latter challenging scenario, but is still under evaluation 8–10,14 …”

“…Beat‐to‐beat verification of atrial pacing is problematic, owing to the small amplitude of atrial‐evoked response (AER), which would make an algorithm prone to underdetecting effective stimulation. The technology required to achieve atrial stimulation by capture verification has only recently been developed, 8–10 and is currently under investigation. To overcome the problem of atrial stimulation verification and meet clinical needs, an algorithm capable of measuring the atrial threshold from indirect evidence has been developed 11–13 .…”