Einthoven's triangle: lead errors and an algorithm for solution.

The three bipolar leads (I, II, and III) of the 12-lead electrocardiogram are subject to technical errors that not only confound interpretation but may lead to faulty clinical actions. While some errors are readily recognized, even experienced electrocardiographers overlook others. This paper reviews the nature of limb lead errors and offers what we think is a generally useful method to deduce the observed, but erroneous, lead configurations.