Monday, June 21, 2021

Neck and Jaw Pain in a patient with a Pacemaker. Sgarbossa Negative. But How about the Modified Sgarbossa Criteria?

I was at home on a late Saturday evening when this first ED ECG was texted to me:

Atrial and Right Ventricular Paced Rhythm
(most pacing is RV pacing --- there is increasing use of biventricular pacing)
What do you think?  What did I say?

"It looks like Occlusion Myocardial Infarction (OMI).  If the clinical presentation is consistent with acute MI, Activate the Cath Lab."

I added this to my text response: "The EKG meets the Smith modified Sgarbossa criteria, so I think there is no choice but to take a look at his coronary arteries, but for some reason I do not feel convinced in my own mind as I look at it." 

I think I was not totally convinced because all the ST segments have very normal upward concavity.  But we have shown that, in LBBB, upward convexity is only present in 50% of leads which meet the Modified Sgarbossa Criteria and are True Positives.

Full Analysis: Leads II, and V4-V6 all have discordant ST Elevation with an ST/S ratio greater than 25%.  In our PERFECT study by Dodd KW et al. (Paced ECG Requiring Fast Emergent Coronary Therapy), which I am told will be published online today in the Annals of Emergency Medicine, just ONE LEAD with such a ratio was highly specific for OMI.   

See post on the the PERFECT study paper here coming soon.  


As for ST Depression in V2: It is NOT concordant, as the Original Sgarbossa Criteria requires.  It is Discordant, but it is excessively discordant (the modified criteria in LBBB established that a single lead with discordant ST/S (if QRS mostly negative) or ST/R (if QRS mostly positive) ratio greater than 30% is nearly 100% specific for OMI -- this has not been validated in the group with a paced rhythm)

Moreover, although there is no definition of hyperacute T-waves for EITHER paced rhythm, LBBB, or normal conduction, these T-waves do appear to be hyperacute.

Important: there is 1) no concordant ST elevation, 2) no concordant ST depression in V1-V3 (or anywhere), and 3) no discordant ST elevation meeting the 5 mm Sgarbossa criteria.  Thus it is NEGATIVE by the Original Sgarbossa Criteria.  In the PERFECT study, 17 diagnoses were made EXCLUSIVELY by the 25% rule; only 2 could be made exclusively by the 5 mm rule.  That is why the Modified Criteria are so much more sensitive.

Also: in the study, the Modified Sgarbossa criteria worked as well on biventricular pacing as on right ventricular pacing.

So this is an inferior-posterior-lateral OMI until proven otherwise, usually due to a very large RCA with lateral branches, but could be a dominant circumflex.

Here is the clinical context:

Presenting complaint: Weakness, Dental Pain

A 50-something male presented with neck and jaw pain for one hour.  

Past History: CAD (coronary artery disease), HLD (hyperlipidemia), Hypertension, Mobitz II with pacemaker placed in 2014 (Medtronic MRI compatible), STEMI (ST elevation myocardial infarction), RCA dissection --- no intervention, Tobacco dependence, Type 2 diabetes mellitus.

He had been seen one day prior at another hospital with the same complaint.

He stated that, when he had the RCA dissection, his symptoms had been similar, but he also suffered from cervical radiculopathy and was followed by a neurosurgeon; he complained that those symptoms had not been adquately addressed.  

On the visit one day prior, an ECG had been done and was negative for OMI/ischemia.  The patient had left AMA.  No troponins were drawn at that visit.

The cath lab was activated.

Later, the ECG from one day prior was obtained:

Sinus rhythm with RBBB, without pacing

45 minutes later, while waiting for the cath team, this was recorded:

There is diagnostic evolution of ST Segments

Angiography:  100% Thrombotic Occlusion of a Dominant Circumflex in the AV groove.

First Abbott Architect high sensitivity troponin returned after the patient left for the cath lab = 70 ng/L.  Upper reference limit = 34 ng/L.

After PCI, with right ventricular pacing:

As you can see, all ratios are in the normal range now.
Highest ratio is in V3 at 2/14 = 14%
There is no longer excessively discordant STD in V2

Notice how the T-waves appear almost as hyperacute as before.  
In V3 and V4, they are nearly 20 mm, almost as tall as before
This suggests that T-wave size is less important in paced rhythm that is the ST/S ratio.
This needs further study in our database.

Post PCI ECG with some conduction of atrial paced beats (without ventricular pacing):

This shows resolution of the ischemia, with inverted (reperfusion) T-waves in inferior and lateral leads.  

There is another interesting finding, too!

There are P-waves which conduct, and RBBB, but there are also pacer spikes just a few milliseconds after the onset of the QRS.  This means that the impulse did not reach the ventricular sensing before the activation of the ventricle, and thus could not inhibit firing of the ventricular lead.  So there is fusion of intrinsic RBBB and a paced beat.

But all ischemia is gone.

Learning Points:

1. Use the Smith Modified Sgarbossa Criteria for diagnosing OMI in ventricular paced rhythm.

2. Stay tuned for the article in Annals of EM online this week.

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