Aortic Valve Disease Screening from PPG via Physiology-Guided Self-Supervised Learning
Aortic valve disease (AVD) represents a major public health burden, while its diagnosis relies on echocardiography, which is limited by cost and specialist expertise, restricting scalable screening and risk stratification. Existing portable sensing modalities are constrained by indirect representations or acquisition dependencies. In this context, photoplethysmography (PPG), a widely available optical signal capturing peripheral hemodynamic dynamics, provides a scalable physiological measurement. However, the scarcity of clinically labeled PPG data severely constrains the development of effective data-driven models. To address this limitation, we propose Physiology-Guided Self-Supervised Learning (PG-SSL), leveraging approximately 170,000 unlabeled UK Biobank PPG recordings. PG-SSL constructs physiologically derived pseudo-labels based on clinically motivated waveform phenotypes associated with aortic stenosis (AS) and aortic regurgitation (AR), enabling large-scale pretraining without AVD-specific labels. Following fine-tuning on a small labeled cohort, the model achieved AUROCs of 0.8025 for AS and 0.7669 for AR. Further analyses demonstrated robustness under clinical confounding and covariate-balanced evaluation, as well as significant longitudinal associations with incident AVD events. This study demonstrates the feasibility of PG-SSL for leveraging large-scale unlabeled physiological signals under clinically labeled data-scarce conditions. The proposed approach provides a useful strategy for improving low-cost PPG-based screening and risk enrichment for clinically recognized AVD.