LECTURES:
1. Basic Components of Cardiac Complex
2. QRS Complex Basics
3. QRS Complex
4. QRS Nomenclature
5. QRS Amplitude
6. QRS Duration (Width)
7. QRS Morphology
8. Intrinsicoid Deflection
9. Full ECG Course
10. The EKG Guy Lectures
Overview
- Cardiac event: ventricular depolarization
- Duration: 60–110 ms (0.60-0.11 s)
- Axis: -30° to +105° (downward & to left)
- Endocardial myocytes depolarization slightly earlier than epicardial myocytes => QRS
QRS Nomenclature:
- Q wave: 1st negative deflection after P wave; not always present (ie, if 1st deflection is not negative, Q wave absent)
- R wave: 1st positive deflection after P wave
- S wave: 1st negative deflection after R wave
- >1 of same wave is named as prime (‘) waves (eg, 2nd R wave named R’ => RSR’)
- Small letters (q, r, s) = deflections of small amplitude (eg, qRS = small q, tall R, deep S)
Significant vs. Insignificant Q waves
- Septal (insignificant) Q wave: often in I, aVL, & V6 from septal innervation
- Pathological (significant) Q wave if: Q wave ≥30 ms wide, Q wave >2 mm deep, Q wave depth ≥1/3 R wave height, or present in V1-V3 => sign of MI
