Friday, June 14, 2024

ECG Blog #434 — WHY Did this Patient Arrest?

The ECG in Figure-1 — was obtained from a middle-aged man who presented to the ED (Emergency Department) in cardiac arrest. ROSC (Return Of Spontaneous Circulation) was obtained — and ECG #1 was recorded.
  • In view of this history — How would YOU interpret the ECG in Figure-1? Should you activate the cath lab?

Figure-1: The initial ECG in today's case. (To improve visualization — I've digitized the original ECG using PMcardio)

MY Initial Thoughts:
Although there are different approaches regarding decision-making as to which patients with ROSC following OHCA (Out-of-Hospital Cardiac Arrest) should undergo prompt cardiac catheterization — what does appear to be clear, is that the post-ROSC ECG helps to identify patients at highest risk who may benefit from coronary reperfusion (Gentile et al — JAHA 12:3027923, 2023 — and — Baldi et al — JAMA Netw Open 4(1): e2032875, 2021).
  • Prompt cath is therefore advised if the post-ROSC shows an acute STEMI.
  • The decision of whether to cath patients with a less definitive post-ROSC ECG is less clear. Waiting a few extra minutes to repeat the ECG in such patients may help reduce false positive results when there are equivocal findings on the initial post-ROSC tracing.

The Post-ROSC ECG in Today’s CASE:
The initial ECG following ROSC in today’s case is clearly abnormal. I’ve highlighted KEY findings in Figure-2.
  • Although there is significant baseline artifact in the limb leads of ECG #1 — the underlying rhythm is sinus — as conveyed by the presence of upright P waves with a constant and normal PR interval in lead II (BLUE arrows in lead II of Figure-2). The rhythm is regular — at a rate just over 100/minute = sinus tachycardia (ie, the R-R interval is just under 3 large boxes in duration).

  • PEARL #1: In general — lead II is the best lead for assessment of P waves to determine if sinus rhythm is present. Sinus rhythm is defined by the presence of upright conducting P waves in this lead. 
  • The above said, when for whatever reason sinus P waves are not well seen in lead II — the 2nd-best lead when looking to determine if sinus rhythm is present, is lead V1. Recognition of a negative P wave deflection with fixed PR interval before the next QRS (similar to that highlighted by BLUE arrows in lead V1 of Figure-1) — confirms that the rhythm in today's ECG is sinus.

 We can tell at a glance in Figure-1 — that the "culprit" causing the artifact in today's ECG is the RA (Right Arm) extremity. The cause of the abnormal baseline deflections seen in Figure-2 is most likely muscle tremor artifact (See Bouthillet T — ACLS Med Training, Dec, 2015). A quick LOOK at the patient would confirm this — but unfortunately, there is no information about the patient's appearance.
  • NOTE: Abnormal baseline deflections in Figure-2 are maximal in leads I,II and aVRAs discussed in ECG Blog #255 — the extremity primarily responsible for a certain type of artifact — can be quickly recognized by the finding of greatest artifact amplitude in 2 of the 3 standard limb leads (ie, in leads I and II for Figure-2) — and, minimally or not seen at all in the 3rd standard limb lead (ie, artifact is minimal in lead III). By Einthoven's Triangle — this localizes the "culprit" extremity to the RA electrode.

  • SHORTCUT (To find the "culprit" extremity within seconds! ): When 2 of the standard limb leads clearly show greater artifact amplitude than the 3rd standard limb lead — then whichever augmented lead shows maximal amplitude indicates the "culprit" extremity (which is lead aVR in Figure-2 = which means that the RA is the "culprit" extremity).
  • Clinically — Rapid determination of the "culprit" extremity may facilitate quick correction (ie, If you could quickly know to look if the RA electrode had become loose — this may be easy to rectify).

Figure-2: I've labeled the initial ECG.

Continuing with assessment of ECG #1 in Figure-2:
  • The rhythm is sinus tachycardia at ~110/minute. The QRS complex is obviously wide. QRS morphology is consistent with RBBB (ie, all positive QRS in right-sided lead V1 — with wide terminal S wave in left-sided leads I and V6).
  • The all negative QRS complexes in each of the inferior leads indicate marked LAD (Left Axis Deviation). That said, rather than LAHB (Left Anterior HemiBlock) — the all-negative QRS in leads II,III,aVF is really a “QS” wave — which therefore suggests inferior MI at some point in time (possibly with or without associated LAHB).

  • The most worrisome part of this tracing is in the chest leads. RED arrows in leads V2,V3,V4 mark the J-point, which defines the end of the QRS complex in these leads. Everything to the right of these arrows entails the ST segment. As can be seen when compared to the dotted RED lines that mark the baseline in these leads — there is marked ST segment elevation, which is most dramatic in leads V3 and V4. This is followed by especially “bulky” (hyperacute) T waves in leads V5,V6, that are clearly taller, “fatter”-at their peak and wider-at-their base than expected given amplitude of the QRS complex in these leads.
  • Adding support to the occurrence of proximal LAD OMI — is the ST elevation that is clearly seen in lead aVL. Although harder to appreciate because of the variable baseline — there is also a hyperacute T wave in lead I.


PEARL #3: Today’s ECG provides an excellent example of T-QRS-D (Terminal QRS Distortion)When present — T-QRS-D may provide invaluable assistance for distinguishing between a repolarization variant vs acute OMI (ie, When true T-QRS-D is present in a patient with new symptoms — it is virtually diagnostic of acute OMI = Occlusion-based Myocardial Infarction)

I illustrate the ECG finding of T-QRS-D below in Figure-3, which I've excerpted from My Comment in the November 14, 2019 post in Dr. Smith's ECG Blog. To review:
  • T-QRS-D — is defined as the absence of both a J-wave and an S-wave in either lead V2 or lead V3 (and/or probably also in lead V4). Although simple to define — this finding may be subtle! It takes a while to become comfortable and confident in its recognition.

A picture is worth 1,000 words. I’ve taken thlead V3 examples in Figure-3 from previous cases posted on Dr. Smith’s ECG Blog:
  • TOP in Figure-3 — Despite marked ST elevation in lead V3 — this is not T-QRS-D, because there is well-defined J-point notching (BLUE arrow). This patient had a repolarization variant as the reason for ST elevation.
  • BOTTOM in Figure-3 — This is T-QRS-D, because in this V3 lead there is no J-point notching — and, there is no S wave (RED arrow showing that the last QRS deflection never descends below the baseline).

Figure-3: Comparison between ST elevation in lead V3 due to a repolarization variant (TOP — from 4/27/2019) — vs acute OMI (BOTTOM — from 9/20/2015), which manifests T-QRS-D (See text).

To Emphasize: The phenomenon of T-QRS-D is not needed in today's case to recognize the acute STEMI. Once the J-point is recognized in the chest leads (RED arrows in leads V2,V3,V4 of Figure-2) — the marked ST elevation becomes obvious.
  • In my experience — T-QRS-D is not a common finding among patients with acute coronary occlusion. That said, the importance of being aware of this phenomenon — is that on occasion other signs of acute OMI may not be obvious, such that seeing T-QRS-D may be a KEY finding in support of acute infarction (See ECG Blog #318).
  • Today's case is also noteworthy in that T-QRS-D is seen in association with RBBB — which has only been described on rare occasions (See the March 28, 2021 post in Dr. Smith's ECG Blog).

CASE Conclusion:
As noted above — the middle-aged man in today's case presented to the ED in cardiac arrest. Retrospective questioning of the driver who brought this patient to the hospital revealed that he was having chest pain as the reason for presenting to the ED. He became unconscious on arrival.
  • A series of VFib episodes followed — each time with successful defibrillation. ROSC (Return Of Spontaneous Circulation).
  • Cardiac cath was not performed — because the interventionist did not recognize the ECG signs of acute MI.


Acknowledgment: My appreciation to Nirdosh Ashok Kumar (from Karachi, Pakistan) for the case and this tracing.




Related ECG Blog Posts to Today’s Case:

  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.

  • ECG Blog #193 — Reviews the basics for predicting the "culprit" artery (as well as reviewing why the term "STEMI" should be replaced by "OMI" = Occlusion-based MI).
  • CLICK HERE  for my new ECG Videos (on Rhythm interpretation — 12-lead interpretation with Case Studies for ECG diagnosis of acute OMI).
  • CLICK HERE  for my new ECG Podcasts (on ECG & Rhythm interpretation Errors — and — Errors in assessing for acute OMI).
    • Recognizing hyperacute T waves — patterns of leads — an OMI (though not a STEMI) — See My Comment at the bottom of the page in the November 8, 2020 post on Dr. Smith's ECG Blog.
    • Recognizing ECG signs of Precordial Swirl (from acute OMI of LAD Septal Perforators— See My Comment at the bottom of the page in the March 22, 2024 post on Dr. Smith's ECG Blog. 

    • ECG Blog #294 — Reviews how to tell IF the "culprit" artery has reperfused.
    • ECG Blog #230 — Reviews how to compare serial ECGs
    • ECG Blog #115 — Shows how dramatic ST-T changes can occur in as short as an 8-minute period.
    • ECG Blog #268 — Shows an example of reperfusion T waves.
    • ECG Blog #400 — Reviews the concept of "dynamic" ST-T wave changes.

    • ECG Blog #337 — A "NSTEMI" that was really an ongoing OMI of uncertain duration (presenting with inferior lead reperfusion T waves).

    • ECG Blog #282 — reviews a user-friendly approach to the ECG diagnosis of the Bundle Branch Blocks (RBBB, LBBB and IVCD).

    • ECG Blog #203 — reviews ECG diagnosis of Axis, Hemiblocks and Bifascicular Blocks.

    • ECG Blog #318 — reviews the concept of T-QRS-D (Terminal-QRS-Distortion).


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