College Answer

• Tri-fascicular block

• Cause:
  • Complete heart block.
• Management:
  • Correct electrolyte and endocrine abnormalities (e.g. K+, thyroid function tests)
  • Consider influence of drug therapies such as digoxin, calcium channel antagonists
  • Investigate for ischaemic heart disease
  • Referral to cardiology unit for further evaluation (?permanent pacemaker)

Discussion

If you are working though these questions systematically in reverse chronological order, this will all sound very familiar. Old man, fall, trifascicular block... This question is a repeat.

Instead of replicating the discussion entry here,  one could refer the gentle reader to the most recent incarnation of this question (Question 18.1 from the first paper of 2013). However, in this incarnation of the SAQ, the college say that the cause was complete heart block. The ECG is borrowed from the LITFL library.

In this ECG, there is:

• Right bundle branch block
• Left axis deviation (Left anterior fascicular block)
• Complete heart block

In summary, for a trifascicular block:

• RBBB should not have any axis deviation
• If there is RBBB and the QRS in leads I and aVF is not upright, you must assume there is some sort of fascicle block.
• A left axis deviation suggests the anterior fascicle has failed;
• Right axis deviation means the posterior fascicle has failed

The AHA/ACCF/HRS recommend anybody with that much conductive tissue disease get a pacemaker. Other possible contributing causes need to be addressed, which could include AV blocker drugs (beta-blockers, calcium channel blockers, digoxin) and electrolyte derangement.