Notes: BORIANI, G., et al.: Atrial Evoked Response Integral for Automatic Capture Verification in Atrial Pacing. Beat-by-beat Autocapture is currently limited to operation in the ventricle with bipolar leads. The authors investigated the integral of the negative-going portion of the atrial evoked response integral (AERI) as a potential resource for verification of atrial capture. Intracardiac electrogram signals were collected from 59 patients (ages 67.8 ± 15.1 years) with bipolar, low polarization atrial leads. The signals were collected over a mean period of 6.1 months (minimum 4 days) after lead implantation. St. Jude Medical Affinity pulse generators were used to perform automatic capture threshold tests while the electrogram signals were recorded by a Model 3510 programming device. These signals were transferred to a personal computer in digital form for later analysis. The AERI was calculated at each programmable pacing voltage until capture was lost. The difference between the polarization integral at loss of capture and evoked response integral with successful capture was sufficient to justify enabling the atrial Autocapture feature in 53 of 59 patients in whom bipolar pacing and unipolar sensing was performed. The authors developed a calibration routine to identify automatically those patients in whom atrial Autocapture could be programmed On, based on the polarization integral at loss of capture, the estimated maximum polarization integral, and the AERI. Preliminary analysis indicated that the AERI is a practical resource for beat-by-beat atrial capture detection when used with low polarization leads. (PACE 2003; 26[Pt. II]:248–252)

Notes: BINNER, L., et al.: Autocapture Enhancements: Unipolar and Bipolar Lead Compatibility and Bipolar Pacing Capability on Bipolar Leads. Beat-by-beat Autocapture maximizes device longevity by minimizing stimulus amplitude while assuring patient safety. Currently, Autocapture permits use of only bipolar leads. The authors have devised a detection method that operates with unipolar and bipolar leads and covers all pacing and sensing combinations (but bipolar pace and sense simultaneously). This new detection method for unipolar sensing uses the integral of the negative portion of the unipolar evoked response as a robust capture detection feature. When using bipolar leads, the method provides the flexibility of bipolar or unipolar pacing. In this study, unipolar ventricular intracardiac electrograms (EGMs) were recorded in 71 patients, 73.7 ± 9.9 years of age; 9 with high polarization, 62 with low polarization. High polarization had polished platinum or activated carbon electrodes. Low polarization had TiN, platinized platinum, or IrOx electrodes. The intracardiac EGMs were recorded 544 ± 796 days after implant. The pacemakers performed an automatic capture threshold test while the intracardiac EGM signals were recorded in a programmer. These digitized signals were saved for off-line analysis. The unipolar evoked response was calculated at up to six (depending on capture threshold) pacing voltages and the polarization integral at 4.5 V and at loss of capture. An automatic calibration algorithm determined if the signal-to-noise ratio was adequate for Autocapture operation. Autocapture was possible with 60 of 62 of the low polarizations, and with 6 of 9 of the high polarizations. The average values from the data collected were: average unipolar evoked response - 4.1 ± 2.1  mV , average peak negative voltage - 10.0 ± 3.7  mV , average polarization 0.3 ± 0.34 mV, and average signal-to-noise ratio (unipolar evoked response/polarization) 38 ± 71. In all cases the algorithm correctly determined the appropriateness of using Autocapture with the electrodes tested and the unipolar evoked response threshold to be used. (PACE 2003; 26[Pt. II]:221–224)