ECG Leads

Basic intro to ECG

1. Electrocardiogram Leads

2. Goedemorgen :

3. Introduction An electrocardiographic lead is pair of electrical conductors For detecting cardiac potential differences. Bipolar leads will make potential differences at different sites . It is a routine diagnostic procedure. It is standardised and has universal conventions

4. What are leads? Leads I, II, and III are bipolar leads Leads aVR , aVL , and aVF are unipolar leads Leads V1–V6 are unipolar leads ♥ Clinical Tip: Patients should be treated according to their symptoms, not merely their ECG.

5. Basic Electrocardiographic Conventions Placed on both arms and the left leg Called Einthoven's triangle Example: lead II electrocardiogram measured between right arm & left leg . upward deflection in a lead II electrocardiogram = an electrical polarity exists between left leg and right shoulder electrodes >>> left leg electrode being positive.

6. Downward deflection in a lead II record > the left leg electrode being negative.

7. How to measure the dipoles? The net dipole is determined by: (1) how extensive the wavefront is? (2) the consistency of orientation between individual dipoles at different points in the wavefront

8. How to measure the dipoles? The net dipole makes: lower portion (+) in contrast to upper portion of body. Postive voltages exists on three sides. from Einthoven's triangle by observing that the net dipole has the arrows point positive direction of leads I, II, and III. Note: dipole is most parallel to lead II. Thus, it has a large component in the lead II direction. >> create a larger voltage on lead II than on leads I or III. Small component on lead III >>oriented nearly perpendicular to lead III.

9. The Standard 12-Lead Electrocardiogram Recorded from 12 different leads. leads I, II, and III > bipolar leads nine leads > unipolar leads. Three leads are generated by using the limb electrodes. Two electrodes > indifferent electrode . Third limb electrode is made the positive pole of the pair. [ augmented unipolar limb leads] The voltage record between the electrode at the right arm and the indifferent electrode = aVR recorded on left arm and lead = aVL recorded from the electrode on left leg = aVF

10. Chest leads six specified positions on the chest wall. precordial or chest leads and are designated as V1 through V6. when positive electrode is in position 1 and wave of ventricular excitation sweeps away from it > deflection downward . When electrode is in position 6 and the wave of ventricular excitation sweeps toward it, > deflection upward.

11. Recap

12. La fin The End النهاية آخر El final