Tuesday, July 13, 2021

Which Modified Sgarbossa Rule does this meet? And what is the Rhythm?

A reader sent this ECG and asked "Steve, can this be hyperK?"  He sent no clinical information.

What do you think?












My answer: "This is inferior OMI."  There is LBBB and an with a false negative Modified Sgarbossa."

The rhythm is also interesting, but does not affect the diagnosis of OMI: there are also no P-waves before the QRS complex.  The wide complex suggests an idioventricular rhythm, in fact it is an accelerated junctional rhythm followed by Left Bundle Branch Block (LBBB).  Idioventricular rhythm would have a slower QRS onset, similar to VT (and it can't be VT also because it is too slow).  So this is an accelerated junctional rhythm with retrograde P-waves and LBBB). (I confirmed this with the rhythm master, Ken Grauer, who annotated the 2nd EKG below to show the retrograde P-waves).

There are obvious hyperacute T-waves in inferior leads and also in V5 and V6, but it does not clearly meet any of the 3 Smith Modified Sgarbossa criteria.  There is some minimal concordant ST elevation in lead III (some might measure 1 mm, but it is not consistent in the only 2 complexes), and just less than 1 mm of concordant ST depression in V1-V3.  There is also no ST elevation that is greater than 25% of the preceding S-wave (no proportionally excessively discordant ST Elevation).  

But there is one other rule that we derived and validated as VERY SPECIFIC, though probably not sensitive, for OMI: Discordant ST depression (or STE) that is out of proportion to the preceding R-wave (or S-wave) in just one lead with an ST/S or ST/R ratio of at least 30%.  If greater than 30%, it is nearly 100% specific.  Lead aVL has 1.25 mm ST depression and 3.75 mm R-wave, for a ratio of 33%.

Some will say "this meets the Barcelona criterion of ST deviation of at least 1 mm discordant with the QRS in any lead with max R or S voltage of no more than 6 mm."  While this is true, the Barcelona criteria should only be mentioned to condemn it.  The methodology was worthless.  See here: Barcelona Rule on Left Bundle Branch Block: Lots of Issues.  See the most critical issue discussed below.

See references for Modified Sgarbossa far below:


Later, there was a follow up ECG:

This shows obvious evolution of inferior and posterior MI.  There is still an accelerated junctional rhythm.


Outcome:

He was taken for angiogram and found a 100% occluded mid RCA and 3 stents were placed.   I do not have troponin or echo data, or followup ECG.



Ken Grauer annotated the 2nd EKG, with explanation below. 


#2 ECG (and this also applies to the first ECG: 

— vertical RED line shows onset of the QRS (so NO sinus P waves). Instead — multiple leads show retrograde P waves (YELLOW arrows). QRS morphology consistent with LBBB (albeit lack of a monophasic R wave in lead V6 …. Of concern is marked primary ST elevation in each of the inferior leads (lead III >> II) — with mirror image reciprocal ST depression in leads I and aVL (much more than what would be expected with simple LBBB). Note J-point ST depression in lead V2 (which is not normal) — and then hyperacute T waves in V5,V6 — so consistent with acute RCA occlusion that results in accelerated junctional escape with LBBB and acute infero-postero-lateral STEMI.

#2 ECG — Junctional rhythm again, albeit at a slightly slower rate + LBBB (albeit still no monophasic R wave in lateral chest leads) — still hyperacute T waves in inferior and lateral chest leads with reciprocal change in aVL — though less ST elevation in ECG #2 (and less J-point ST dep in aVL)

Of note — Lack of lateral chest lead R wave may reflect loss of lateral forces from the STEMI.

References for Smith Modified Sgarbossa Criteria


The Barcelona Criteria are based on Fatally Flawed Research

This is an excerpt from a paper I am writing with some colleagues.  A critique of the "Barcelona Criteria," which should only be mentioned to condemn it.


The final area of contention regards the inappropriately low cTn threshold ratios (peak level divided by upper reference limit) utilized by the authors of the Barcelona study. Di Marco et al. used a cTn ratio of 10, in reference to a separate study by Gonzalez et al [1]. This was a mistaken representation of Gonzalez et al. who had incorrectly stated that their cTn assay had a 99% URL cutpoint of >0.001 µg/L (1ng/L, or 0.001 ng/mL). This was incorrect, as there is no assay on the market with a URL that low, including all high sensitivity (hs) cTn. Using this URL, a peak cTn ratio of 10 gives a cut-point of 0.010 ng/mL, which is not only a very low cutoff for occlusion, but also too low to make the diagnosis of any MI, as it is far lower than the URL for almost all assays available, whether 4th or 5th generation hs-cTn [2].

 

In the Smith validation study, by comparison, the vast majority of cTnI measurements were done using an assay with URL of 0.032 to 0.050 ng/mL (µg/L). Thus, the cTnI ratio required to diagnose OMI was far greater (>200-300x the URL for cTnI, and >100x the URL for cTnT) than the Barcelona study. The proven TIMI 0-1 Occlusion MI groups in the Smith criteria studies consistently demonstrated mean peak cTnI levels >10ng/mL, and peak cTnT levels in the 2.0-6.0 ng/mL (µg/L) range. This highlights that for a reference standard of OMI, the troponin cutoff must be in the range of >100x the URL.

 

As expected with the inappropriately low troponin threshold in the Barcelona study, the online supplemental information stated that 95% of all AMIs in the study were considered “STEMI equivalents.” This contrasts with the known prevalence of true STEMI and of OMI among AMI with normal conduction. For example, Hillinger et al. found only 81 STEMIs (18%) and 54 additional OMIs (13%), for a total of 135 OMI (31%) among 438 AMIs in their large, prospective real world chest pain cohort [3].


1. Gonzalez MA, Porterfield CP, Eilen DJ, Marzouq RA, Patel HR, Patel AA, et al. Quartiles of peak troponin are associated with long-term risk of death in type 1 and STEMI, but not in type 2 or NSTEMI patients. Clin Cardiol. 2009 October 01;32(10): 575-583.

2. Hillinger P, Strebel I, Abacherli R, Twerenbold R, Wildi K, Bernhard D, et al. Prospective validation of current quantitative electrocardiographic criteria for ST-elevation myocardial infarction. Int J Cardiol. 2019 October 01;292: 1-12.

3. Collinson PO, Saenger AK, Apple FS and IFCC C-CB. High sensitivity, contemporary and point-of-care cardiac troponin assays: educational aids developed by the IFCC Committee on Clinical Application of Cardiac Bio-Markers. Clin Chem Lab Med. 2019 April 24;57(5): 623-632.










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