Atrioventricular Block: 1st Degree

ECG Features

Figure 1: ECG Strip[1]

A first degree atrioventricular (AV) block occurs when electrical impulses moving through the AV node are delayed but not blocked.[2] A first degree AV block is present when the PR interval exceeds 0.30 sec.

Table 1: ECG Characteristics[2]

Clinical Significance[3]

  • A first degree heart block does not cause haemodynamic disturbance; thus, no specific treatment is needed.

ECM Features

Additional Information


  1. First Degree Heart Block [Online image]. (2013). Retrieved July 19, 2016, from
  2. First Degree Heart Block. (n.d.). Retrieved July 27, 2016, from
  3. First Degree Heart Block. (n.d.). Retrieved August 8, 2016, from