First degree heart blocks are common and often the result of high vagal tone. In this situation, increasing the heart rate to a higher level, i.e. 100 bpm or more, by doing some exercise, and repeating the ECG, should see a normalisation of the PR interval. A conduction defect must be suspected if the PR interval does not normalise, or if the PR interval increases over time.

The PR interval can occasionally be found to be very prolonged. If normalising with exercise, this is likely to be due to a very high vagal tone in a healthy individual.

The combination of AV block and a bundle branch block however suggests the existence of a conduction tissue disorder.

Mobitz I (Wenkebach) AV block may be seen in normal individuals during sleep. However, the presence of second degree block requires investigation as those can occasionally progress to complete block.

Mobitz II AV block and complete heart blocks are generally not acceptable.

Information to be provided

On the first occasion that the PR interval is abnormal (i.e. ≥210 ms); or if the PR interval has increased since last investigated.

  • ECG following exercise to raise the heart rate;
  • A cardiologist report in the case that a Mobitz I (Wenkebach) AV block has been identified), this should generally include a Holter monitoring.


  • An applicant presenting with a first degree AV block that normalises [<200 ms] during exercise may be considered as having a condition that is not of aeromedical significance.
  • An applicant presenting with second degree AV block, Mobitz I type, should be considered as having a condition that is of aeromedical significance, unless a previous AMC has considered the condition to be of no ongoing aeromedical significance;
  • An applicant with a second degree AV block, Mobitz II, or third degree AV block, should be considered as having a condition that is of aeromedical significance.