Automatic threshold measurement and output adjustment are used as default settings in modern pacemakers. The purpose of the study was to assess Atrial Capture Management (ACM) of Medtronic pacemakers in pediatric patients.
Forty children were enrolled in two centers. Median age was 9.8 years (range 0.8-17.5 years). Half had undergone surgery for congenital heart defects; 45% of patients had an epicardial atrial lead. The pacing indication was atrioventricular block in 82% of patients and sinus node disease in 18%. Manually determined atrial thresholds and ACM measurements were compared.
ACM measurements were within the expected variation in 37/40 (93%) of the patients. In one patient the threshold was 0.625-V lower manually than with ACM. One patient had too high an intrinsic atrial rate for ACM to be able to measure threshold. The mean threshold at 0.4 ms was 0.69 +/- 0.32 V manually and 0.68 +/- 0.35 V with ACM (two-tailed paired t-test, P = 0.52) in all patients. The mean difference was 0.012 V (95% confidence interval: -0.027, 0.053). The mean endocardial threshold was 0.70 +/- 0.36 V manually and 0.69 +/- 0.38 V with ACM; epicardial threshold was 0.67 +/- 0.27 V manually and 0.68 +/- 0.32 V with ACM. The difference between the measurements was 0.012 V for endocardial and 0.014 V for epicardial leads. No atrial arrhythmias due to ACM measurements were observed.
ACM measures atrial thresholds reliably in pediatric patients with both endocardial and epicardial leads, allowing its use in both. Constant high intrinsic atrial rate may prevent automatic threshold measurement in young children.