Mystery ECG – Would You Send This to the Cath Lab?

May 17, 2023

Written by Ketan Patel

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Presented is a discussion of ECG and clinical findings in the setting of a ventricular paced rhythm (and other wide QRS complex rhythms) that could signal the presence of occlusion myocardial infarction (OMI).

Why does this matter?
Adhering strictly to STEMI criteria to identify OMI by ECG will miss candidates for reperfusion, a delay which may be compounded in the setting of wide complex QRS rhythms. 

Non-elevations that warrant escalation
The presented case is a 70-year-old patient with a classic story for myocardial infarction (MI), who has a pacemaker. In addition to this ECG, the patient also had an episode of polymorphic ventricular tachycardia.

Applying the Smith-modified Sgarbossa criteria to this ECG gives clues to the presence of OMI (which are also applicable in cases in Left Bundle Branch Block):

• Subtle concordant ST elevation in lead III (Please see original article or really zoom in on lead III).

• Reciprocal concordant ST depression in I and aVL. (Please see original article or really zoom in on leads I, L, and V6)

The application of the Smith-modified Sgarbossa criteria has been validated in both left bundle-branch block rhythms and paced rhythms when any of the following are present:

• 1 mm concordant ST elevation in any lead
• 1 mm concordant ST depression in V₁-V₃
• Excessive discordant ST elevation (ST/S ratio over 25%)

It can clue you into the presence of OMI with 81% sensitivity.

While the above ECG findings don’t strictly meet the criteria of the Smith-modified Sgarbossa criteria, there are additional clues to OMI in recognizing the Aslanger pattern when you combine the following with the finding of ST elevation in lead III only:

• ST-segment in lead V₁ that is higher than V₂.
• Concordant ST depressions in V₂-V₆.

The above pattern – identified by Aslanger, though not a classic STEMI – has been shown to identify OMI with additional critical stenoses.

In this case, the above ECG findings, along with the electrical instability in the clinical course should all lead to the discussion of emergent reperfusion.

Editor’s note: Friends, this ECG is subtle…really subtle. Be sure you consider ST elevation per the ACC 4th universal definition of MI, which is the baseline onset of the Q wave (PR segment) and onset of the ST segment (J point). If you zoom in on lead III, you’ll see a 0.5mm ST elevation. ~Clay Smith

Source
McLaren JTT, Meyers HP, Smith SW. Chest Pain, Paced Rhythm, and 2 Missed Indications for Emergent Reperfusion. JAMA Intern Med. 2023 Apr 3.