Diagnostic performance of wearable acoustic–electrocardiographic indices for screening secundum atrial septal defect in children

Objective To evaluate the diagnostic performance of acoustic–electrocardiographic indices derived from a wearable phonocardiogram–electrocardiogram (ECG) sensor for screening secundum atrial septal defect (ASD) in children. Methods In this cross-sectional study, 50 children (4–12 years) with secundum ASD and 50 age- and sex-matched healthy controls were enrolled. A wearable patch device recorded synchronized single-lead ECG and phonocardiogram, and S2 splitting time, S1–S2, S1–S2/RR (%), EMAT and EMAT/RR (%) were derived from artifact-free sinus beats at end-expiration. Group differences were assessed using independent-samples t -tests or χ 2 tests. Receiver operating characteristic analysis evaluated the ability of S2 splitting time and S1–S2/RR (%) to detect ASD, with optimal cut-offs defined by the Youden index. Multivariable logistic regression examined the independent association of these indices with ASD. Results Baseline demographic, anthropometric, and hemodynamic variables were well balanced between ASD and control groups. Compared with healthy controls, children with ASD had significantly prolonged S2 splitting time (39.65 ± 8.37 vs. 28.20 ± 8.91 ms; t = 6.623, P < 0.001) and an increased systolic fraction S1–S2/RR (%) (37.53 ± 2.39% vs. 34.47 ± 2.99%; t = 5.653, P < 0.001), whereas S1–S2 interval, EMAT, and EMAT/RR (%) did not differ significantly between groups. ROC analysis showed that S2 splitting time had good discriminative ability for detecting ASD, with an area under the curve (AUC) of 0.831 [95% confidence interval (CI): 0.752–0.910]. A cut-off value of ≥31.75 ms yielded a sensitivity of 0.90 and a specificity of 0.66. S1–S2/RR (%) demonstrated acceptable discrimination, with an AUC of 0.776 (95% CI 0.686–0.866) and an optimal cut-off of ≥35.25% (sensitivity 0.88, specificity 0.60). In multivariable logistic regression, both S2 splitting time [odds ratio (OR): 1.19 per 1-ms increase; 95% CI: 1.09–1.29; P < 0.001] and S1–S2/RR (%) (OR: 1.58 per 1% increase; 95% CI: 1.25–2.00; P < 0.001) remained independently associated with ASD. Conclusions Wearable acoustic–electrocardiographic monitoring enables quantitative assessment of S2 splitting and systolic time fractions in children. Prolonged S2 splitting time and increased S1–S2/RR (%) are characteristic of secundum ASD and show good diagnostic performance, supporting these simple indices from a patch-type phonocardiogram–ECG sensor as a practical non-invasive tool for pediatric ASD screening.