Einthoven’s law or Einthoven’s equation for ECG leads – Cardiology MCQ – Answer

Einthoven’s law or Einthoven’s equation for ECG leads

It is regarding potentials in standard ECG limb leads (I, II and III) and can be stated as:

Correct answer: b) I + III = II

This means that the orientation of standard limb leads is in such a way is that sum of potentials of in leads I and III equals that in lead II. Einthoven’s triangle [1] is formed by these leads as sides and theoretically has the heart at its electrical centre, though it may seem too much of a simplification if you go into exact principles of physics.

Reference

1. Schocken K. The Validity of Einthoven’s Triangle Rule. Cardiologia 1939;3:197–202.

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