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

ECG High Grade AV block 4 to 1 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).
ECG Strip 4 to 1 AV block


Advanced Reading



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Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

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