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Parallel-Learning of Invariant and Tempo-variant Attributes of Single-Lead Cardiac Signals: PLITA
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Proposes PLITA, a BYOL-based self-supervised method for single-lead ECG that adds a tempo-variant loss so that temporally closer segments have closer representations, alongside an invariant loss across recordings of the same subject.
Problem
Existing self-supervised methods for single-lead ECG capture only invariant (subject-level) attributes and neglect tempo-variant patterns that evolve over a recording, which matter for tasks like AFib detection and sleep staging.
Approach
Combines a BYOL-style invariant loss (positives from different recordings of the same subject) with a tempo-variant loss that matches cosine-distance matrices among time-sorted windows of the same record to an ideal |i-j|/(N-1) temporal distance matrix, using separate projectors for the two attribute kinds.
Key results
- On AFib classification with SHHS pretraining, PLITA reaches 80.7% accuracy and 78.4 F1, versus 76.6% accuracy for BYOL.
- On sleep stage classification with SHHS pretraining, PLITA reaches 75.3% accuracy and 0.81 AUC, versus 73.8% and 0.79 for Mix-Up.
- On gender identification PLITA is competitive but not best (76.5% accuracy vs 76.7% for BYOL with SHHS pretraining).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add the tempo-variant loss to the invariant-learning objective (ablation) | PLITA · Tempo-variant-related downstream tasks | performance | Helped |
| Use PLITA instead of BYOL | ViT ECG representations · AFib classification, SHHS pretraining | accuracy: 76.6 -> 80.7 | Helped |
| Use PLITA instead of BYOL | ViT ECG representations · AFib classification, Icentia pretraining | accuracy: 75.3 -> 80.0 | Helped |
| Use PLITA instead of Mix-Up | ViT ECG representations · Sleep stage classification, SHHS pretraining | accuracy: 73.8 -> 75.3 | Helped |
| Use PLITA instead of BYOL | ViT ECG representations · Sleep stage classification, Icentia pretraining | accuracy: 73.3 -> 74.8 | Helped |
| Use PLITA instead of BYOL | ViT ECG representations · Gender identification, SHHS pretraining | accuracy: 76.7 -> 76.5 | Hurt |
| Use PLITA instead of BYOL | ViT ECG representations · Gender identification, Icentia pretraining | accuracy: 66.7 -> 66.5 | Hurt |
| Use N=3 rather than N=4 inputs per recording (ablation) | PLITA · AFib classification, SHHS pretraining | accuracy: 80.7 -> 79.5 | Hurt |
| Use N=5 rather than N=4 inputs per recording (ablation) | PLITA · AFib classification, SHHS pretraining | accuracy: 80.7 -> 77.3 | Hurt |
| Use W=90 rather than W=120 seconds (ablation) | PLITA · AFib classification, SHHS pretraining | accuracy: 80.7 -> 76.6 | Hurt |
| Use W=150 rather than W=120 seconds (ablation) | PLITA · AFib classification, Icentia pretraining | accuracy: 80.0 -> 79.4 | Hurt |
| Use W=150 rather than W=120 seconds (ablation) | PLITA · Sleep stage classification, Icentia pretraining | accuracy: 74.8 -> 72.9 | Hurt |
Surprising findings
- Gender classification, a purely invariant task, shows PLITA not outperforming BYOL and PCLR, which the authors attribute to the invariant objective being shared.
Limitations
- Evaluated only with a ViT architecture.
- Only BYOL is used for the invariant objective; other non-contrastive frameworks such as DINO or VICReg are not tested.
- Icentia pretraining yields lower performance on some tasks, attributed to noise in the data.
Experimental setup
Datasets: SHHS Icentia MIT-AFIB MIT-PSG Cinc2017
Benchmarks: MIT-AFIB MIT-PSG SHHS Cinc2017
Metrics: accuracy F1 score AUC
Baselines: PCLR CLOCS Mixing-Up Ti-MAE Siamese Masked Autoencoders BYOL
Builds on: BYOL PCLR CLOCS Siamese Image Embeddings ViT
Closest papers by meaning
- From Token to Rhythm: A Multi-Scale Approach for ECG-Language Pretraining (ICML 2025 · similarity 0.88)
- Guiding Masked Representation Learning to Capture Spatio-Temporal Relationship of Electrocardiogram (ICLR 2024 · similarity 0.88)
- Reading Your Heart: Learning ECG Words and Sentences via Pre-training ECG Language Model (ICLR 2025 · similarity 0.86)
- GEM: Empowering MLLM for Grounded ECG Understanding with Time Series and Images (NeurIPS 2025 · similarity 0.85)
- Boosting Masked ECG-Text Auto-Encoders as Discriminative Learners (ICML 2025 · similarity 0.84)
- Leveraging an ECG Beat Diffusion Model for Morphological Reconstruction from Indirect Signals (NeurIPS 2024 · similarity 0.84)
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