> There’s a strong history of useful signals from single lead ecgs. But to be clear, a single lead ECG requires two electrodes at a minimum and commonly a thir

> There’s a strong history of useful signals from single lead ecgs. But to be clear, a single lead ECG requires two electrodes at a minimum and commonly a third as ground. So a single lead ECG will have minimum two cables attached to electrodes on the patient. The placement depends on which lead (eg lead I, lead II, etc) but there's always two minimum.