High Grade AV block
Second degree heart block with a P:QRS ratio of 3:1 or higher, producing an extremely slow ventricular rate.
ECG Example of High-grade AV block
- High-grade AV block (4:1 conduction ratio).
- Atrial rate is approximately 140 bpm.
- Ventricular rate is approximately 35 bpm.
- Broad QRS complexes suggest that this may be due to Mobitz II block (see “fixed ratio blocks” for a discussion of this concept).
- AV block: 1st degree
- AV block: 2nd degree, Mobitz II
- AV block: 2nd degree, “fixed ratio blocks” (2:1, 3:1)
- AV block: 3rd degree (complete heart block)
- Eponymythology: History of Second-degree AV block.
- Eponym. Karel Frederik Wenckebach (1864 -1940).
- Eponym. Woldemar Mobitz (1889 – 1951).
- Eponym. John Hay (1873 – 1959).
LITFL Further Reading
- ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis – ECG interpretation in clinical context
- ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
- 100 ECG Quiz – Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS – the best of the rest
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric
- Wagner GS. Marriott’s Practical Electrocardiography 12e
- Chan TC. ECG in Emergency Medicine and Acute Care
- Rawshani A. Clinical ECG Interpretation
- Mattu A. ECG’s for the Emergency Physician
- Hampton JR. The ECG In Practice, 6e