Monday, October 10, 2016

A patient with a ventricular paced rhythm and chest pain

One of my residents who just graduated saw this patient and sent the case:

This 80-something patient presented with chest pain.  He had recently had a pacer placed for complete heart block and had not had an angiogram at that time.  Ischemia had not been suspected.

He had this ECG recorded:
There is sinus rhythm.  There is clearly a DDD pacer that detects the sinus activity and then paces the ventricle (necessary when there is complete AV block).  The pacing is in the right ventricle (all QRS negative in V1-V6, showing that the lead is in the apex of the RV).
There is some concordant ST elevation in aVL (but not 1 mm).  

There is reciprocal ST depression in II, III, aVF.
There is discordant ST elevation [opposite to a negative QRS (i.e. S-wave)] in V1-V5.
The cardiologist interpretation was "concerning for ischemia."
Is it excessively discordant ST elevation?
In V1, the J-point is 4 mm above the PQ Junction and the S-wave is 14 mm:

The ratio is 28%

We do not know for certain what excessive is in paced rhythm.

The Smith-modified Sgarbossa criteria were derived and validated in Left Bundle Branch Block, which is similar to, but not the same as, ventricular paced rhythm.  For LBBB, an ST/S ratio greater than 25% is very specific and sensitive for acute coronary occlusion. 

Can we apply the rule to paced rhythm?

I don't know for sure, but I do it and we are in the middle of a large multi-center study to try to figure it out.

Here it isPaced Electrocardiogram Requiring Fast Emergent Coronary Therapy (PERFECT) Study.

Importantly, 50% of physicians who care for patients with chest pain believe that you cannot diagnose STEMI in the presence of paced rhythm. This is definitely not true and an old teaching that should be thrown away.

The emergency physician activated the cath lab.  He writes that "Cardiologist thought you could not see the ischemic changes on paced ECG."

In the meantime, an old ECG was found:
The change is obvious and makes the first ECG diagnostic.
The discordant ST elevation in V1-V3 in this old ECG is proportional.
The patient had an acute 100% LAD occlusion.


  1. Deep and large Q wave in aVL compared to old ECG suggests MI

  2. In V6 there looks like to be concordant STD??

  3. Really interesting case ... I love studying the ECG and extrapolating every information I can from it. But in this occasion an emergency echo might have offered valuable information towards ischemia, showing apical or anterior walls akinesia. How do you explain the axis deviation in leads V5-V6 between the two ECGs ? Could it be lead missplacement in one of the two ?

    1. Costas,
      Probably some lead migration. When in the RV apex, all of V1-V6 should be negative. If the lead is a bit out of the apex, then V5 and V6 can be positive.
      Steve Smith

  4. Yet another interesting and instructive post. Thank you.

    Can you comment also - in V6, arguably subtle concordant ST changes and if so should this contribute to the probably of acute occlusion?

  5. Dr. Smith, for me it looks like there is also concordant ST Depression in V6

  6. Dear sir, can we do thrombolysis in the presence of a pace maker, if STEMI occured in a patient. ?


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