QRS Complex (Adult) – The Premier EKG Resource for Medical Professionals

Question of the day

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

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DID YOU KNOW?

Dr. Anthony Kashou (The EKG Guy) is a physician resident at the Mayo Clinic in Rochester, Minnesota. He is on a mission to transform ECG education and filling the gap exists around the world. Dr. Kashou has taught and developed curriculum for medical students, including 500+ lectures and 100+ hours of adult and pediatric ECG lessons.

At the Mayo Clinic, he pursues innovative ECG research and was awarded first place for his research at the Minnesota American College of Cardiology Conference 2018. His passion for medical education and innovation led to the development of EKG.MD, which provides a convenient and accessible forum to learn the fundamentals and foundations of ECG interpretation. He has also authored dozens of peer-reviewed articles for medical journals and textbooks, along with multiple ECG books for learners at all levels.

Dr. Kashou continues to lead and teach weekly ECG sessions and weekend seminars for residents, nurses, ECG interpreting technicians, and physician assistants at the Mayo Clinic. He has been asked and is currently developing an ECG board review course for cardiology fellows. He has an online following of over 275,000 individuals and is the founder of the largest, fastest growing ECG community in the world. His clinical research focuses on developing innovative ECG algorithms that can be integrated and implemented into clinical practice.

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