What Do You Think 54

This week, Ben from Royal Melbourne Hospital sent me this ECG to interpret.

What do you think?
‍

The first step is to determine the rhythm.

• Is it sinus rhythm?
• Is there AV conduction?

• Sinus rhythm (red arrows).
• Sinus cycle 740 ms (81 bpm).
• First degree AV block (260 ms).
• Narrow QRS
• Suggestion of Wenckebach AV block at the end of the tracing with increasing PR intervals (yellow arrows) but no dropped beat seen.
• A sinus P wave does not conduct as it lies in the refractory period of the previous premature beat (red stippled arrow).  

‍

There are other P waves present.

• Premature P waves with a different configuration to the sinus P waves and are atrial ectopics, mostly in bigeminy(blue arrows).
• Most are premature non-conducted atrial ectopics (blue stippled arrows) that reset the sinus cycle.

• Two atrial ectopics conduct with a long PR interval (yellow highlight and blue arrows). This suggests that the fast pathway is still refractory and the atrial ectopic conduct to the ventricle via the slow pathway. Whenever, I see slow pathway conduction, the fast pathway AV conduction is always slower than normal (PR about 220 to 300 ms)suggesting some disease in the fast pathway, to allow the slow pathway to emerge.  

There is still one P wave unaccounted for (purple arrow).

I suggest that this is also anon-conducted atrial ectopic as part of a couplet.

The sinus cycle is 740 ms which explains the ectopic-sinus coupling intervals.

In summary:

• Sinus rhythm with first degree AV block.
• Sinus cycle 740 ms.
• Conducted and non-conducted atrial ectopics inbigeminy terminated by an atrial couplet.
• Non-completed Wenckebach AV sequence.

‍

Harry Mond