Electrical performance and automatic capture characteristics of a 3.5-mm(2) passive fixation lead during 1-year follow-up.

BACKGROUND: Bipolar low polarization electrodes are recommended for a regular AutoCapture (St. Jude Medical, Inc., Sylmar, CA, USA) function in order to effectively detect the evoked response (ER) signal. The objective of this national multicenter registry was to evaluate the electrical performance and the AutoCapture characteristics of the bipolar ventricular pacing lead IsoFlex S, model 1636T or 1646T (St. Jude Medical), in combination with single- and dual-chamber pacemakers. METHODS: Ventricular pacing and sensing thresholds, lead impedance, ER amplitude, and polarization signals were measured at discharge and routine follow-up visits after 1, 3, 6, 9, and 12 months. AutoCapture activation was recommended based on the results of the ER sensitivity test. RESULTS: Of the 252 patients initially included, 109 (43%) have completed the follow-up. The mean ventricular pacing threshold was 0.43 +/- 0.19 V at discharge and 0.68 +/- 0.32 V at 12 months postimplant. The values for the ventricular sensing threshold were between 9.51 +/- 4.12 and 9.99 +/- 4.09 mV at discharge and at the 12-month follow-up. The unipolar lead impedance decreased from 533 +/- 94 to 476 +/- 73 ohms during the follow-up. The mean ER amplitude was 16.47 +/- 6.70 mV at discharge and 17.42 +/- 7.43 mV after 12 months, and the corresponding mean polarization signals were 0.59 +/- 1.00 and 0.74 +/- 1.24 mV, respectively. AutoCapture activation was recommended in at least 95% of the patients investigated over the 12-month follow-up. CONCLUSION: The bipolar ventricular pacing lead IsoFlex S 1636/1646T shows a good electrical performance and is mostly compatible with the AutoCapture algorithm.

Evaluation of the atrial evoked response for capture detection with high-polarization leads.

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.