ECG Challenge 2

This 80 years old female presented in emergency with history of dizziness from one day. She was hypertensive, on medicines from the past 15 years.

So, the first thing you notice in this ECG? The bradycardia with 'couplets' is easily identifiable. What else do you see in this ECG? Let's make a complete break down step by step

First of all, where all the P waves? On first impression we don't appreciate any P waves. That, obviously, means that the sinus node is not firing. Although, on closer inspection, a few P waves can be appreciated in the Inferior leads (II, III, aVF) and aVL, just after the T wave, highlighted in the image below.

See, these P waves circled in the inferior leads are inverted. This tells us that these P waves are not originating from the Sinus node but, in fact, from around the Coronary Sinus. Coronary Sinus is present close to the AV node, at the 'bottom' of the atria and all activity generating in that area spreads upwards into the atria. The directional of current flow is opposite to that coming from the sinus node when seen from the angle of Inferior leads, thus it appears negatively in the inferior leads.

However, as you can observe this is true for every second complex, the first complex is still devoid of any P wave. Those beats are thus arising from the AV node with no electric current in the atria recorded. These have been underlined in orange color in the following image.

Nodal ectopics underlined in orange color

So, here we have 2 different foci generating the rhyhtm; the Coronary sinus and the AV Node. It is difficult to ascertain if these both foci are 'in sync' or just firing independantly in a timely manner. But we can confidently conclude that the sinus node is not generating any activity what so ever.

This is thus a case of Sinus node dysfunction / Sinus arrest with the coronary sinus and the AV node taking over!

Please comment below if you want to add something or correct me.