What types of leads are there in ECG?

In electrocardiography (ECG), there are different types of leads used to record the electrical activity of the heart from different angles and positions. Here are some of the common types of leads:

1. Limb Leads:

- Lead I: Measures the electrical activity between the left arm (negative electrode) and the right arm (positive electrode).

- Lead II: Measures the electrical activity between the right arm (negative electrode) and the left leg (positive electrode).

- Lead III: Measures the electrical activity between the left arm (negative electrode) and the left leg (positive electrode).

2. Chest Leads:

- V1: Placed on the right sternal border, in the fourth intercostal space.

- V2: Placed on the right sternal border, in the fourth intercostal space, but slightly to the left of V1.

- V3: Placed between V2 and V4.

- V4: Placed in the fifth intercostal space, on the mid-clavicular line.

- V5: Placed in the same horizontal line as V4, but at the anterior axillary line.

- V6: Placed in the same horizontal line as V4 and V5, but at the mid-axillary line.

3. Augmented Limb Leads:

- aVL (augmented vector left): Measures the electrical activity between the left arm (negative electrode) and the average of the right arm and the left leg (positive electrode).

- aVR (augmented vector right): Measures the electrical activity between the right arm (negative electrode) and the average of the left arm and the left leg (positive electrode).

- aVF (augmented vector foot): Measures the electrical activity between the left leg (negative electrode) and the average of the right arm and the left arm (positive electrode).

4. Modified Limb Leads:

- Modified Lead I: Measures the electrical activity between the left arm (negative electrode) and the right leg (positive electrode), similar to Lead I but with a different electrode positioning.

- Modified Lead II: Measures the electrical activity between the right arm (negative electrode) and the left foot (positive electrode), similar to Lead II but with a different electrode positioning.

5. Right Ventricular Leads:

- V3R and V4R: These leads are used to specifically record the electrical activity of the right ventricle and are placed on the right side of the chest.

By combining these different leads, a 12-lead ECG is usually obtained, which provides a comprehensive overview of the electrical activity of the heart from various angles.