Long-term performance of beat-to-beat automatic ventricular threshold adjustment in infants with congenital atrioventricular block.

BACKGROUND

AutoCapture™ (AC) of St. Jude Medical (SJM; St. Paul, MN, USA) pacemakers provides beat-to-beat ventricular capture verification and allows low-amplitude pacing. There has been concern about evoked response signal (ERS) amplitude decreasing over time, leading to discontinuation of AC. The purpose of this study was to evaluate the long-term performance of AC in infants with epicardial pacing leads.

METHODS

Data on 16 newborns with congenital complete atrioventricular block (CCAVB) implanted with a SJM Microny pacemaker between January 1998 and December 2004 were collected. The ERS at discharge, at 12 ± 2 months, and long-term AC performance were analyzed retrospectively. The median follow-up time was 5.3 years (range 0.4-8.6 years), the end point of follow-up being either lead or generator exchange.

RESULTS

AC could be activated in all patients at discharge; the median ERS was 9.3 mV (3.7-19.0 mV). At 12 ± 2 months, the median ERS measured 4.6 ± 3.6 mV (n = 13), showing a significant decrease (P = 0.002) and leading to discontinuation of AC in three (23%) of 13 patients. AC use was possible in eight patients and long-term use in six patients.

CONCLUSIONS

In epicardially paced CCAVB newborns, the ERS amplitude decreased significantly during the first year. ERS decrease was the most common reason for AC failure. At 1-year follow-up, AC was functional in only 53% of patients, although it could originally be activated in all patients. During the first year of follow-up, special attention to AC parameters is recommended in this subgroup of pediatric pacemaker patients.