The following is a summary of “Prospective Evaluation of High Titer Autoantibodies and Fetal Home Monitoring in the Detection of Atrioventricular Block Among Anti-SSA/Ro Pregnancies,” published in the November 2023 issue of Rheumatology by Buyon et al.

Researchers started a prospective study called Surveillance To Prevent Atrioventricular Block Likely to Occur Quickly (STOP BLOQ) to assess the influence of anti-SSA/Ro titers and the effectiveness of ambulatory monitoring in the detection of fetal second-degree atrioventricular block (AVB).

Based on commercial testing results, they stratified women with anti-SSA/Ro autoantibodies, categorizing them into groups with high and low anti–52-kD and/or 60-kD SSA/Ro titers using at-risk thresholds determined in previous evaluations of AVB pregnancies. The high-titer group had fetal heart rate and rhythm monitoring (FHRM) thrice daily and echocardiography weekly/biweekly from 17 to 26 weeks. Abnormal FHRM triggered urgent echocardiography for AVB identification.

The results showed that 261 out of 413 participants (63%), anti–52-kD and/or 60-kD SSA/Ro titers, met monitoring thresholds, with an AVB frequency of 3.8%. No cases occurred with low titers. AVB incidence rose with higher levels, reaching 7.7% in the top quartile for anti–60–kD SSA/Ro and escalating to 27.3% in participants with a prior child with AVB. Levels from 15 participants with paired samples showed healthy pregnancies were not explained by decreased titers. Abnormal FHRM occurred in 45 of 30,920 recordings, with 10 confirmed AVB cases identified. Seven second-degree AVB cases occurred <12 hours from normal FHRM and within 0.75 to 4 hours of echocardiogram. One participant was diagnosed with second/third-degree and two with third-degree AVB via urgent echocardiogram >17 to 72 hours from FHRM. No AVB was detected in surveillance echocardiograms with normal preceding FHRM recordings.

They concluded that high-titer antibodies were associated with an increased incidence of AVB, but anti-SSA/Ro titers remained stable over time, suggesting that other factors were required.

Source: acrjournals.onlinelibrary.wiley.com/doi/full/10.1002/art.42733