Will Two Do? Varying Dimensions in Electrocardiography: The PhysioNet/Computing in Cardiology Challenge 2021

The electrocardiogram (ECG) is a non-invasive representation of the electricalactivity of the heart. Although the twelve-lead ECG is the standard diagnosticscreening system for many cardiological issues, the limited accessibility oftwelve-lead ECG devices provides a rationale for smaller, lower-cost, andeasier to use devices. While single-lead ECGs are limiting[1], reduced-lead ECG systems holdpromise, with evidence that subsets of the standard twelve leads can captureuseful information [2],[3],[4] and even be comparable totwelve-lead ECGs in some limited contexts. In 2017 we challenged the public toclassify AF from a single-lead ECG, and in 2020 we challenged the public todiagnose a much larger number of cardiac problems using twelve-leadrecordings. However, there is limited evidence to demonstrate the utility ofreduced-lead ECGs for capturing a wide range of diagnostic information.In this year's Challenge, we ask the following question: **' Will two do?'**This year's Challenge builds on last year'sChallenge[5], which asked participants toclassify cardiac abnormalities from twelve-lead ECGs. We are asking you tobuild an algorithm that can classify cardiac abnormalities from twelve-lead,six-lead, four-lead, three-lead, and two-lead ECGs. We will test eachalgorithm on databases of these reduced-lead ECGs, and the differences inperformances of the algorithms on these databases will reveal the utility ofreduced-lead ECGs in comparison to standard twelve-lead EGCs.