A Cardiac Evoked Response Algorithm Providing Threshold Tracking: A North American Multicenter Study

Abstract

The purpose of this study was to evaluate a pacing system using the recognition of cardiac evoked response for the automatic adjustment of pacing output. Patients were prospectively followed after primary implantation of VVIR pacemakers using AutoCapture (St. Jude Medical CRMD). Sensing and pacing thresholds, polarization signal, evoked response, and AutoCapture performance were evaluated with serial visits and 24-hour Holter monitoring. Three hundred ninety-eight patients (mean age 71 +/- 15 years) were followed for an average duration of 1 year (3 days-1.75 years) with the algorithm functional in > 90% of patients. Backup pacing in the event of exit block was confirmed in all patients. Pacing thresholds remained stable at 0.89 +/- 0.34 V with a pulse width of 0.31 ms (with chronic output autoset at 0.3 V above the actual threshold). Evoked response exhibited a small but statistically significant increase with time (8.92 mV at implant, 9.60 mV at 12 months), however, this finding did not result in any change in AutoCapture function during our follow-up period. The polarization signal remained stable with minimal variation (1.12 mV at implant, 1.18 at 12 months). No clinical adverse events were observed using the AutoCapture algorithm. In this initial experience with the AutoCapture algorithm the evoked response and polarization measurements remained adequate, allowing the system to function in the majority of patients with safe, low output pacing. High energy backup pacing provided an added safety feature over fixed output devices in cases of unexpected threshold rises. Longer follow-up is required for continued long-term validation of the algorithm.

Long‐Term RV Threshold Behavior by Automated Measurements: Safety is the Standpoint of Pacemaker Longevity!

“…Further FU were scheduled every 6 months until the RVPT showed fluctuations ≤1 V; otherwise, insertion of a new RV lead could be considered. Based on literature 4–7 and on former clinical experience on medium‐term threshold behavior 1,8–11 showing that safety margins as threshold + 0.25 V/0.5 V achieve, respectively, 99.4%–99.8% effective ventricular stimulation, we decided to use an output at least as threshold + 1.5 V to accommodate RVPT fluctuations, when output programmings were switched to a fixed‐output setting instead of AVC.…”

Atrial Threshold Variability: Implications for Automatic Atrial Stimulation Algorithms

“…Pacing by capture verification of the stimulation threshold has become the gold standard in ventricular pacing since the release of the first Autocapture TM‐featured pacemaker in 1994 1 . Over the last decade, the development of algorithms for the automatic detection of the ventricular pacing threshold and for the adjustment of ventricular output have improved patient safety and increased pacemaker longevity 2–7 . Moreover, automatic measurement of the pacing threshold and automatic output adjustment will be fundamental features of the remote monitoring of pacemaker/implantable cardioverter defibrillator (ICD) patients in the near future.…”

Performance Evaluation of a Right Atrial Automatic Capture Verification Algorithm using Two Different Sensing Configurations

“…Several methods to detect paced events that depolarize or capture the myocardium have been developed and applied to the various chambers of the heart. One such method evaluates changes in the evoked response (ER) signal characteristics to discriminate captured events from non‐captured events and to determine the threshold through identification of persistent loss of capture 14–31 . Use of the ER signal characteristics for the ACV algorithm poses design constraints due the relative size of the ER signal to the significantly larger pacing artifact that remains on the lead‐tissue interface after a paced event.…”