High Grade AV block definition
- Second degree heart block with a P:QRS ratio of 3:1 or higher, producing an extremely slow ventricular rate.
- Unlike 3rd degree heart block there is still some relationship between the P waves and the QRS complexes.
- High-grade AV block may result from either Mobitz I or Mobitz II AV block.
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).
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Hampton, JR. The ECG In Practice, 6e
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
- Wagner, GS. Marriott’s Practical Electrocardiography 12e
- Chan, TC. ECG in Emergency Medicine and Acute Care
- Mattu, A. ECG’s for the Emergency Physician
LITFL Further Reading
- ECG BASICS — Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis –alphabetical diagnostic approach to the ECG
- ECG CLINICAL CASES — ECG’s placed in clinical context with a challenging Q&A approach
- 100 ECG Quiz — Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS — the best of the rest
- LITFL ECG IMAGE Database — Searchable database of LITFL ECG’s
- ECG and Cardiology Eponymous Syndromes — Cheats guide to eponymous emancipation
- ECG Exam Template — a framework for answering ECG exam questions.