Wednesday, December 28, 2022

ECG Blog #353 — Why the Wide QRS? - T-QRS-D

The ECG in Figure-1 represents a pattern you should recognize — so, NO history is given. How would YOU interpret this tracing?

Figure-1: The ECG in today's case. No history provided ...

MY Thoughts on the ECG in Figure-1:
At first glance — the rhythm in Figure-1 looks like a wide-QRS rhythm. But the QRS is not wide. Instead, the underlying rhythm is sinus, as indicated by upright sinus P waves in lead II (RED arrow in Figure-2).
  • The teaching point lies with assessment of QRS duration. The reason the QRS looks wide — is that it "blends in" with neighboring ST segments that are either markedly elevated or depressed. As a result — the boundary between the end of the QRS complex and the beginning of the ST segment becomes indistinguishable in many parts of this tracing.
  • This is "Shark Fin" morphology — which most often reflects severe transmural ischemia from acute OMI = Occlusion-based Myocardial Infarction (See ECG Blog #265 and ECG Blog #296 for additional examples of this phenomenon).

To Confirm Shark Fin Morphology:
The KEY for confirming the presence of Shark Fin morphology — is to find 1 or 2 leads in which you can clearly define the limits (end point) of a QRS complex. 
  • The most helpful lead for doing so in today's case is lead I — in which I've drawn in a BLUE line parallel to the heavy grid ECG line in simultaneously-recorded leads I,II,III. Note that I've extended this line down to the corresponding complex in the long lead II rhythm strip (Figure-2).
  • The reason for continuing the BLUE line all the way down to the corresponding beat in the long lead II rhythm strip — is that this tells you where the QRS complex ends and the ST segment begins in the long lead II rhythm strip (ie, Blue arrows in the long lead II rhythm strip highlight the end of the QRS complex).
  • Knowing this landmark for the complexes in the long lead II rhythm strip — allows us to draw in and extend upward the BLUE lines parallel to the heavy ECG grid line in the other 3 sets of simultaneously-recorded leads.

Putting It All Together:
The ECG in Figure-2 shows sinus rhythm at ~95/minute, with an extreme amount of  "Shark Fin" ST segment deviation in multiple leads: 
  • In the 3 inferior leads (II,III,aVF) — there are Q waves with a marked amount of ST elevation (seen to the right of the BLUE lines in Figure-2).
  • There is a comparable amount of reciprocal ST depression in lead aVL (with a lesser amount of ST depression in lead I, in which the QRS complex is much smaller).

  • In the chest leads — ST elevation begins in lead V3, and continues with Shark Fin morphology in leads V4,V5,V6. Small but-definitely-present Q waves are seen in each of these leads.
  • An initial positive deflection (r wave) is preseved in leads V1,V2. Shark Fin morphology ST depression is seen in these 2 anterior leads.

  • BOTTOM Line: In a patient with new chest pain — the ECG shown in Figure-2 is diagnostic of a diffuse, ongoing acute event. IF due to a single "culprit" vessel — I'd suspect acute occlusion of a dominant LCx (Left Circumflex) coronary artery, given infero-postero-lateral involvement. More likely — this patient has severe underlying multi-vessel disease, with acute occlusion of one of the remaining sources of coronary flow.

Figure-2: The rhythm in today's tracing is sinus (RED arrow in lead II). Vertical time lines highlight how to assess QRS duration.

  • Did YOU notice T-QRS-D in lead V3 of Figure-2?


T-QRS-D: An Underappreciated ECG Sign:
The concept of Terminal QRS Distortion (T-QRS-D) was unknown to me prior to my active participation as an Associate Editor in Dr. Smith's ECG Blog. Since then I've seen many patient cases that validate the clinical utility of this ECG finding promoted by Dr. Stephen Smith. 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). 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. Although simple to define — this finding may be subtle! I fully acknowledge that it has taken me 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 this 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).

Regarding Today's Case:
Clearly — We do not need to identify T-QRS-D in today's case to confirm the large acute OMI. That said — I find it helpful to appreciate that T-QRS-D is present in lead V3 (GREEN arrow in Figure-2) because: i) There is no J-wave in this lead; and, ii) There is no S wave (because the last QRS deflection in lead V3 of today's tracing 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).

FOLLOW-Up in Today's CASE:
My follow-up on today's case is limited. Today's ECG is from a 57-year old man who presented for chest pain. Cardiac cath revealed severe multi-vessel disease — including proximal RCA and LAD occlusion, with diffuse LCx disease.
  • Prediction of this patient's coronary anatomy is admittedly academic — since prompt cath with acute reperfusion will be indicated regardless of what our prediction might be.
  • That said — the reason I suspected that the "culprit" lesion would not only be an acutely occluded proximal LAD (Left Anterior Descending) — was the lack of ST elevation in the more anterior leads (ie, in leads V1,V2).
  • While true that LAD occlusion (so-called "wraparound" lesions) can result in ST elevation in both inferior and anterior lead areas — we would not expect this extreme amount of inferior lead ST elevation if the sole lesion was a "wraparound" LAD.
  • Dominant LCx occlusion may produce the distribution of acute ST-T wave changes seen in today's ECG. That said — a "Take-Home" Point to keep in mind, is that severe underlying multi-vessel disease is a common setting for extensive areas of acute involvement that don't seem consistent with what you would predict from acute single-vessel occlusion.


Acknowledgment: My appreciation to Chun-Hung Chen (from Taichung City, Taiwan) for the case and this tracing.


ADDENDUM (12/28/2022): 

  • For review of the concept of Shark Fin ST deviation ...

TECG Media PEARL #73 (5:40 minutes Audio) — Reviews the concept of "Shark Fin" Selevation and depression as a sign of extensive acute infarction.




Related ECG Blog Posts to Today’s Case: 

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

  • ECG Blog #265 — and ECG Blog #296 — for examples of Shark Fin ST deviation.

  • The November 22, 2019 post in Dr. Smith's ECG Blog — My Comment (at the bottom of the page) adds to this case, in which there was cardiac arrest, ischemic Osborn waves, with massive Shark Fin ST deviation from acute STEMI.
  • The June 12, 2018 post in Dr. Smith's ECG Blog — My Comment (at the bottom of the page) adds to this case, in which there was an underlying Bifascicular Block (RBBB/LPHB), in addition to Shark Fin ST elevation & depression. 
  • The January 24, 2020 post in Dr. Smith's ECG Blog — My Comment (at the bottom of the page) adds to this case, in which there was an underlying Bifascicular Block (RBBB/LPHB) in addition to Shark Fin ST elevation & depression — followed by progressive Low Voltage due to Myocardial Stunning from the huge infarct.

  • ECG Blog #318 — Reviews the concept of T-QRS-D (Terminal-QRS-Distortion) — as a sign of acute OMI.


  1. Great interpretation and a timely reminder of the Terminal QRS distortion which is quite common. Lovely read! My student, Lilian alerted me to this post and we are impatiently waiting for 354. Thanks Professor KG