Prospective Evaluation of High Titer Autoantibodies and Fetal Home Monitoring in the Detection of Atrioventricular Block Among Anti‐SSA/Ro Pregnancies.

Objective: This prospective study of pregnant patients, Surveillance To Prevent AV Block Likely to Occur Quickly (STOP BLOQ), addresses the impact of anti‐SSA/Ro titers and utility of ambulatory monitoring in the detection of fetal second‐degree atrioventricular block (AVB). Methods: Women with anti‐SSA/Ro autoantibodies by commercial testing were stratified into high and low anti–52‐kD and/or 60‐kD SSA/Ro titers applying at‐risk thresholds defined by previous evaluation of AVB pregnancies. The high‐titer group performed fetal heart rate and rhythm monitoring (FHRM) thrice daily and weekly/biweekly echocardiography from 17–26 weeks. Abnormal FHRM prompted urgent echocardiography to identify AVB. Results: Anti–52‐kD and/or 60‐kD SSA/Ro met thresholds for monitoring in 261 of 413 participants (63%); for those, AVB frequency was 3.8%. No cases occurred with low titers. The incidence of AVB increased with higher levels, reaching 7.7% for those in the top quartile for anti–60‐kD SSA/Ro, which increased to 27.3% in those with a previous child who had AVB. Based on levels from 15 participants with paired samples from both an AVB and a non‐AVB pregnancy, healthy pregnancies were not explained by decreased titers. FHRM was considered abnormal in 45 of 30,920 recordings, 10 confirmed AVB by urgent echocardiogram, 7 being second‐degree AVB, all <12 hours from normal FHRM and within another 0.75 to 4 hours to echocardiogram. The one participant with second/third‐degree and two participants with third‐degree AVB were diagnosed by urgent echocardiogram >17 to 72 hours from an FHRM. Surveillance echocardiograms detected no AVB when the preceding interval FHRM recordings were normal. Conclusion: High‐titer antibodies are associated with an increased incidence of AVB. Anti‐SSA/Ro titers remain stable over time and do not explain the discordant recurrence rates, suggesting that other factors are required. Fetal heart rate and rhythm (FHRM) with results confirmed by a pediatric cardiologist reliably detects conduction abnormalities, which may reduce the need for serial echocardiograms. [ABSTRACT FROM AUTHOR]