3KG v2: Universal Electrocardiogram Representations for Label-Efficient Phenotype Discovery

We propose 3KG v2, a new self-supervised learning method for universal representation learning of electrocardiograms. This method builds upon its predecessor by featuring a new contrastive objective and transformation space. We assess the quality of representations generated by this algorithm by transferring pre- trained models from a large public dataset to various downstream tasks, including some with- out prior clinical association with ECGs. Performance evaluation is conducted in both few- shot and full data settings to account for limited and complete training data availability, respectively. For each task, we perform a linear evaluation to assess the effectiveness of the pretrained representations. For tasks in the full- data setting, we additionally perform a full-fine tuning to determine the performance ceiling of each method in a practical deployment scenario.

Our results demonstrate that 3KG v2 consistently outperforms a randomly initialized model trained solely on the target task across all downstream tasks and settings. Specifically, we achieve state-of-the-art performance in few- shot diagnosis of right ventricular function and aortic valve stenosis, two conditions that typically require large amounts of labeled ECGs for effective model training. Moreover, we find that fine-tuning 3KG v2 on our source task’s labels can lead to exceptional transfer capability across a variety of tasks. Notably, our model demonstrates a high level of accuracy in predicting left atrial volume index, achieving a 0.720 C-index even in a few-shot setting. This achievement appears to be unprecedented, as we are not aware of any other ECG model that performs well on this task. While 3KG v2 out- performs our baselines and shows promising results on the majority of phenotype discovery tasks, there is still room for improvement in the absolute performance of any ECG model on many of these complex tasks. Further research is warranted to continue developing and improving such methods for phenotype discovery tasks on ECGs.