Explain Einthoven's Triangle and the limb leads (I, II, III) in an ECG.

Here's a breakdown of the leads mentioned:

• Lead I (LA - RA or VL - VR): This lead records the electrical potential difference between the left arm (LA) and the right arm (RA). In terms of voltage, it's the voltage at the left arm minus the voltage at the right arm ($V_L - V_R$).
• Lead II (LL - RA or VF - VR): This lead records the electrical potential difference between the left leg (LL) and the right arm (RA). In terms of voltage, it's the voltage at the left leg (foot) minus the voltage at the right arm ($V_F - V_R$).
• Lead III (LL - LA or VF - VL): This lead records the electrical potential difference between the left leg (LL) and the left arm (LA). In terms of voltage, it's the voltage at the left leg (foot) minus the voltage at the left arm ($V_F - V_L$).

These three leads (I, II, III) form Einthoven's Triangle, a fundamental concept in ECG interpretation.