Long-Term Performance of Beat-to-Beat Automatic Ventricular Threshold Adjustment in Infants with Congenital Atrioventricular Block
Address for reprints: Anita Hiippala, M.D., PL 281, 00029 Helsinki, Finland. Fax: +358947175306; e-mail: firstname.lastname@example.org
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.
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.
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.
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.