LECTURES:
1. Electrodes
2. Vectors & Electrodes
3. Complete ECG Course
4. The EKG Guy Videos
Overview
- Electrodes sense electrical activity in heart (ie, impulses traveling below them) => EKG machine registers activity at electrodes & converts impulses to waves on EKG paper
- Standard 12-lead ECG: 10 electrodes (4 on limbs + 6 on precordium) monitor 12 leads
- “Cameras” providing 3-D image of heart’s electrical activity => EKG
- Electrical impulse moving:
- AWAY from electrode => downward (negative) deflection
- TOWARD electrode => upward (positive) deflection
- PERPENDICULAR to electrode => isoelectric deflection
- Multiple electrodes around heart => 3-D picture of heart’s electrical axis = EKG
Extremity Electrodes
- L-arm, R-arm, N (neutral, R leg), F (foot, L-leg)
- Does not matter if electrodes attached proximal or distal on extremity (best to be uniform)
Chest Electrodes
- V1: 4th intercostal space, R of sternum
- V2: 4th intercostal space, L of sternum
- V3: b/t V2 & V4
- V4: 5th intercostal space in midclavicular line (under L-breast in women)
- V5: b/t V4 & V6
- V6: same height as V4 in midaxillary line; horizontal to V4, so not necessarily 5th intercostal space
- V3R-V6R: right-sided chest leads (on R-chest; mirror to normal L-side placement)
- V3R: R-midclavicular line
- V4R: V4, but R-sided
- V5R: b/t V4R & V6R
- V6R: same height as V4R in midaxillary line; horizontal to V4R, so not necessarily 5th intercostal space
- V7-V9: posterior leads (on back)
- V6 => V7
- V5 => V8
- V4 => V9
Abbreviations: L, left; R, right; b/t, between