ECG of the Week - 18th February 2013 - Interpretation

Final part of the ECG trilogy.

 

The nursing staff come and get you to say the patients rhythm has changed on the monitor and they've ran off a new ECG.

 

 

 

 

Click to enlarge

Rate:

• Ventricular 90 - 100 bpm

Rhythm:

• Ventricular paced
• Subtle irregularity

Axis:

• LAD (-70 deg)

Intervals:

• QRS - Prolonged (160-180 ms)
• QT - 480ms (QTc Bazette ~ 580 ms)

Segments:

• ST Elevation II, III, aVF, V4
• ST Depression I, aVL
• All ST changes discordant to QRS

Additional:

• T wave Inversion I, aVL, aVR, V1-2
• Notching in leads V1-3
• ? Atrial activity rate ~150 bpm although appears somewhat irregular
• Would a Lewis lead configuration have helped ? Read more about the Lewis lead on one of our earlier ECGs here.
• RBBB morphology  – different again from QRS morphology on ECGs 1 & 2
• Subtle QRS alternans – Thanks to Christopher and Vince for spotting this one
• Final complex is only partially included but morphology appears different with ? p wave post pacing spike with fusion morphology - Thanks to Vince for pointing this out

I would encourage all our readers to take a look at the comments from both Christopher & Vince on this one.

Vince raises an interesting point regarding the QRS alternans being a potential marker for ischaemia in the setting of a paced rhythm although I don't know much about this phenomenon and will try to source some literature evidence (Vince - any pointers ?)

Christopher correctly points out that RBBB morphology in a presumed RV paced rhythm is unusual, a quick literature search reveals a number of case reports on this topic. I've linked to one freely available paper in the reference section that gives a nice brief overview of RBBB morphology and RV pacing.

I, like Christopher, am no pacemaker ninja. I will update this post once I hear from our cardiology / emergency physician co-authors on this one.  I agree with both Christopher and Vince that it is the most interesting ECG of this trilogy and highlights again the need for a thorough and systematic interpretation of an ECG, as at first glance this appears to be 'just' a paced rhythm.

References / Further Reading
 

 

Papers

• Erdogan O, Aksu F. Right bundle branch block pattern during right ventricular permanent pacing: Is it safe or not? Indian Pacing Electrophysiol J. 2007 Jul-Sep; 7(3): 187–191. Full text here