ECG Interpretation: ECG Blog #424 — Proportionality and the "Cut Off"

The ECG in Figure-1 was obtained from a middle-aged woman — who presented with low back pain, shortness of breath and marked hypertension — but no CP (Chest Pain).

QUESTIONS:

In view of this history — How would YOU interpret this ECG?
Are the large, peaked T waves (especially in lead V2) — likely to indicate hyperacute deWinter T waves?

Figure-1: The initial ECG in today's case.

PEARL #1: Did YOU notice that S wave amplitude is cut off in leads V2 and V3? (and possibly also in lead V1).

As a result — We have no idea how deep the S wave really is in these leads! This is especially true in lead V2, given slight-but-real separation between descending and ascending limbs of the S wave in this lead (See dotted RED lines highlighting abrupt S wave "cut-off" in Figure-2).
It is extremely likely that voltage criteria for LVH (as listed in the ADDENDUM below in Figure-3) would have been easily satisfied IF this ECG had been recorded at half-standardization, so as to enable us to capture full dimensions of the QRS complex in the anterior leads. Given the age of today's patient — and her markedly elevated BP on exam, the finding of LVH is not at all unexpected.
KEY Point: In the United States, there is a limit to the amount of voltage that prehospital ECGs in most EMS (Emergency Medical) Systems are able to display. As a result — QRS amplitudes are automatically truncated once they exceed that limit (which typically is 10 mm for the deepest S wave and tallest R wave).
Once aware of this automatic truncation of ECG amplitudes that is used in most EMS systems in the United States — it becomes EASY to spot (as shown below in Figure-2).

Figure-2: I've labeled with dotted RED lines the S wave "cut-off" in leads V2,V3. I've also added the mirror-image view of leads V2,V3 (within the RED inserts) — showing how likely it is that today's patient has LVH (See text).

More Technical Misadventures in Today's CASE:

In addition to automatic truncation of anterior S waves — 2 additional "technical misadventures" are seen in today's tracing:

There is significant baseline artifact. Although worse in leads aVR,aVL,aVF — fine undulations alter the baseline in virtually all leads in Figure-2. While we are still able to interpret ST-T wave morphology — this baseline artifact clearly renders our assessment less clear.
The lead V1 ectrode is most probably placed too high on the chest because: i) There is an rSr' complex in lead V1; ii) QRS morphology in lead V1 looks very similar to QRS morphology in lead aVR; and, iii) There is a significant negative component to the P wave in lead V1 (See ECG Blog #274 — for review on how to quickly recognize too-high electrode lead placement of leads V1,V2). Since the focus of our attention in today's case is on the anterior leads — alteration of ST-T wave appearance in lead V1 because of erroneous placement of the lead V1 electrode clearly affects our interpretaton.

PEARL #2: Sometimes with LVH — instead of seeing tall R waves with LV "Strain" in the lateral chest leads — we see the "mirror-image" opposite picture in right-sided leads V1,V2 (ie, LVH may be manifested by deep anterior S waves — with ST elevation in leads V1,V2 and/or V3). This is precisely what we see in today's case!

LOOK at the RED inserts in Figure-2 — that show the mirror-image of leads V2 and V3. The dotted RED line highlights that the R wave of this inverted complex would almost certainly be a good bit taller — IF there wasn't "automatic truncation" of the S waves in leads V2,V3 on this EMS ECG.
DON'T the ST-T waves in these inverted RED inserts look identical to the ST-T wave appearance of LV "strain"? (ie, Panel C in Figure-4 below in today's ADDENDUM).
KEY Point: The concept of "proportionality" is essential to recognize! Today's patient with marked hypertension has LVH that is manifest on ECG by deep anterior S waves (in leads V1,V2,V3) — except that these S waves are "cut off" because of the automatic truncation inherent in this EMS ECG. As a result, the ST elevation (with especially tall, peaked T wave in lead V2) — is not indication of acute ischemia. Instead, it is the manifestation of LV "strain" that is best seen in this anterior lead. IF anterior S wave depth would not have been cut off — then the tall, peaked T wave in lead V2 of Figure-2 would probably be proportional to the deep S wave in this lead.
A picture is worth 1,000 words. For additional examples of this phenomenon whereby automatic truncation of an EMS ECG may mistakenly result in LVH serving to mimic ischemia — Check out My Comment at the bottom of the page of the following posts in Dr. Smith's ECG Blog — the November 29, 2023 post — June 20, 2020 — March 31, 2019 — March 29, 2019 — and the December 27, 2018 post.

PEARL #3: Another reason why some clinicians may have been concerned about anterior (or anteroseptal) infarction from today's initial ECG — is the Poor R Wave Progression (ie, There is virtually no r wave in Figure-2 until lead V4!).

While it may not be possible on this single ECG to absolutely rule out anterior (anteroseptal) infarction at some point in time — it's important to remember that marked LVH that is primarily manifest by deep anterior S waves (rather than by tall lateral R waves) — produces a vector in which the hypertrophied, posterior-lying left ventricle opposes normal anterior forces. Thus, it is at least in part because of the deep anterior S waves from LVH that R wave progression in Figure-2 is much less than expected.

PEARL #4: The remaining finding of note on today's ECG — relates to the ST segment coving with symmetric T wave inversion in leads V5,V6 of Figure-2.

The KEY lies in the history. Today's patient is a middle-aged woman who presented with low back pain, shortness of breath and marked hypertension — but no chest pain.
As suggested by Figure-4 below in the ADDENDUM — assessment of the ST-T waves in leads V2,V3 and V5,V6 — is consistent with ischemia and/or LV "strain". While perfectly appropriate to obtain serial ECGs and troponin values in this acutely ill patient — I suspect troponins will be negative, and serial ECGs will confirm that there is no acute OMI.
The PEARL is that LVH with "strain" may mimic ischemia — and this ECG finding of lateral lead ST coving with symmetric T wave inversion is often seen in patients who present with marked hypertension, especially in the absence of new chest pain as a presenting complaint.

FINAL Thoughts:

I unfortunately do not have clinical follow-up on today's case. That said — My final thoughts on the case include:

The need to find out WHY this patient is short of breath.
Wanting to see the initial hospital ECG — in which there should be no limitation of voltage on the ECG recording. I would expect this hospital ECG to show very deep anterior S waves, consistent with LVH.
Ruling out an acute event (As noted above — I would expect serial ECGs and troponins to be negative for acute OMI).

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Acknowledgment: My appreciation for anonymous donation of today's case.

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Related ECG Blog Posts to Today’s Case:

ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.
ECG Blog #73 — Reviews "My Take" on the ECG Diagnosis of LVH.
ECG Blog #92 — Presents another perspective for ECG Diagnosis of LVH.
The November 4, 2018 post in Dr. Smith's ECG Blog — My Comment (at the bottom of the page) reviews 3 ECG Clues for rapid recognition of erroneous lead V1,V2 placement.
For cases similar to today, in which LVH may mimic ischemia — Check out My Comment at the bottom of the page of the following posts in Dr. Smith's ECG Blog — the November 29, 2023 post — June 20, 2020 — March 31, 2019 — March 29, 2019 — and the December 27, 2018 post.
ECG Blog #266 — Reviews some considerations when distinguishing between deWinter T Waves vs Posterior MI.
ECG Blog #183 — Reviews a case of deWinter T Waves (with the Audio Pearl in this post discussing some variants of the deWinter T wave pattern).
ECG Blog #53 — and ECG Blog #340 — Review more cases of deWinter T Waves.
ECG Blog #218 — Reviews HOW to define a T wave as being Hyperacute?
ECG Blog #230 — Reviews HOW to compare Serial ECGs (ie, "Are you comparing Apples with Apples or Oranges?").