AV block: 2nd degree, “high-grade” AV block

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).

Related Topics

• 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

Advanced Reading

• 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