Saturday, December 4, 2021

ECG Blog #266 (74): deWinter T waves or Post. MI?


The patient whose initial ECG is shown in Figure-1 — is an older man with cardiac risk factors, who presented to the ED (Emergency Department) with a history of chest discomfort for ~1 month, that became more severe on the day of admission. 

 

QUESTION:

  • What is the "culprit" artery? WHEN did the event occur?
  • Does this ECG suggest Posterior Infarction or deWinter T waves?


Figure-1: Initial ECG in the ED from a patient admitted with a 1-month history of chest discomfort.

 

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NOTE: Some readers may prefer at this point to listen to the 6:45-minute ECG Audio PEARL before reading My Thoughts regarding the ECG in Figure-1. Feel free at any time to refer to My Thoughts on these tracings (that appear below ECG MP-74).

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Today's ECG Media PEARL #74 (6:45 minutes Audio) — Reviews how to distinguish between deWinter TWaves vs Posterior Infarction.

 

 

 

MY Approach to the ECG in Figure-1:

As always — I favor a Systematic Approach for interpretation of every ECG I encounter (This Systematic Approach is reviewed in ECG Blog 205).

  • Rate & Rhythm: Although we do not have a long lead rhythm strip — we can see that the rhythm is irregularly irregular at a ventricular rate between ~70-to-110/minute. P waves are absent — therefore the rhythm is AFib (Atrial Fibrillation) with a controlled ventricular response.

  

QUESTION:

  • Could it be that the small, upright spikes that are seen in lead V1 (but not in other leads) represent AFlutter (Atrial Flutter) instead of AFib?

 

 

ANSWER:

Although at first glance — the repetitive, small upright spikes that are seen in lead V1 might suggest AFlutter — several ECG findings are against this hypothesis:

  • Many of the leads in Figure-1 show obvious baseline artifact. When multiple other leads show clear sign of baseline artifact — this makes it much more likely that unusual deflections in another lead will also turn out to be artifact.
  • The small spikes in lead V1 look geometric (straight). The baseline in this lead wanders — and — caliper measurement of the small spikes confirms that the distance between one spike deflection and the next is notconsistent.
  • None of the other 11 leads show regularly-occurring atrial activity.
  • The ventricular rhythm is irregularly irregular.
  • AFib is far more common than AFlutter.
  • BOTTOM Line: AFlutter is typically a very regular atrial rhythm — that in the untreated patient, usually manifests an atrial rate close to 300/minute (250-350/minute range). While possible to have AFlutter with variable ventricular conduction — most often the ventricular response will be regular or show group beating. Flutter waves are usually evident in more than a single lead — and are generally better defined that the deflections seen in lead V1. Therefore — the small spike deflections in Figure-1 represent artifact. The underlying rhythm in this tracing is AFib with a controlled ventricular response.

  

PEARL #1: Did YOU note the Low Voltage in the limb leads? (ie, the QRS complex in all 6 leads does not exceed 5 mm). As we are about to contemplate the possibility of acute or recent infarction — it is helpful to be aware of potential causes associated with low voltage.

  • Relevant potential causes to consider in today's case include: i) Pericardial effusion; ii) Takotsubo cardiomyopathy; andiii) A large acute (or recent) infarction, that may result in myocardial "stunning" (See ECG Blog #262 for more on this subject).

 

 

Continuing with My Systematic Approach:

  • Intervals (PR/QRS/QTc): There is no PR interval — since the rhythm is AFib. The QRS complex is narrow — and, the QTc is not prolonged
  • Axis: The frontal plane QRS axis is difficult to assess — because of the very low voltage in all 6 limb leads (with near isoelectric complexes in all limb leads except lead I). The fact that the tiny QRS complex in lead I appears to be all positive suggests that rather than an "indeterminate" axis, the frontal plane axis is probably within the normal quadrant of 0-to-90 degrees.
  • Chamber Enlargement: Probably none — although there is a small-but-predominant R wave in lead V1 (which I discuss momentarily).

 

Regarding Q-R-S-T Changes in ECG #1:

  • Q Waves — Considering how small QRS complexes are in each of the inferior leads — the Q waves present in leads IIIII and aVF are large (ie, at least equal in amplitude to the height of the R wave in each corresponding inferior lead). These Q waves are diagnostic of an inferior infarction, that has occurred at some point in time.
  • R Wave Progression — Although assessment of the QRS complex in lead V1 is made more difficult by the artifactual spikes in the baseline and the tiny size of the QRS — the fact remains that the R wave is predominant in lead V1 (ie, there is no S wave at all in this lead).

 

PEARL #2: In your assessment — Did YOU account for the Tall R Wave in Lead V1? As I emphasize in ECG Blog #248 — the QRS complex will normally be predominantly negative in lead V1. As a result — Whenever you encounter a predominant R wave in lead V1 (as we see in Figure-1 of today's case) — Consider the following 6 Potential Causes (discussed in detail in the Audio Pearl in Blog #248):

  • WPW (Wolff-Parkinson-White) Syndrome.
  • RBBB (Right Bundle Branch Block).
  • RVH (Right Ventricular Hypertrophy).
  • Posterior Infarciton.
  • Hypertrophic Cardiomyopathy.
  • Normal Variant — which is a diagnosis of exclusion. 

The fact that the QRS complex in Figure-1 is narrow immediately rules out WPW and RBBB. Other than the tall R in lead V1 — there are no other findings suggestive of RVH in today's tracing (ie, No right axis — no RAA — no RV "strain" — and no deep S waves persisting to leads V5 and V6). There is no suggestion of hypertrophic cardiomyopathy (ie, No criteria met for LVH) — and this tracing is clearly not a "normal variant". Therefore — the predominant R wave in lead V1 of Figure-1 is most likely to represent a posterior infarction.

 

 

Finally — Regarding ST-T Wave Changes:

  • We've already noted the presence of significant Q waves in each of the inferior leads. Although substantial baseline artifact makes assessment of ST-T waves more difficult in these inferior leads — there does appear to be ST segment coving with slight ST elevation, followed by deep, symmetric T wave inversion in leads II, III and aVF.
  • The "magical" mirror-image opposite relationship of the ST-T waves between leads III and aVL is seen in Figure-1 (This concept discussed in detail in ECG Blog #184). Although subtle — the scooped ST segment with relatively tall T wave peaking in lead aVL is the mirror-image opposite of the ST coving with slight ST elevation elevation, followed by T wave inversion that we see in lead III. This relationship confirms that there has been recent or acute inferior MI.
  •  
  • In the chest leads — We've already noted the small-but-predominant R wave in lead V1, consistent with possible posterior MI.
  • R wave predominance continues in leads V2 and V3.
  • There is significant ST depression that begins in lead V2 — becomes maximal in leads V3 and V4 — and then persists through to lead V6. This is associated with a rapidly rising T wave upstroke that peaks in the form of a 10+ mm T wave in lead V3.

 


Putting IAll Together:

The clinical question that prompted me to present today's case was whether the ECG picture in Figure-1 was more suggestive of posterior infarction or deWinter T waves?

  • The ECG finding known as deWinter T waves is characterized by the presence of giant T waves that are typically seen in 2 or more anterior leads, often beginning with some J-point ST depression — and rapidly rising to tall, widened T waves that tower over the corresponding R wave in the lead you are looking at. By way of illustration — I've adapted Figure-2 from the original deWinter manuscript (2008, NEJM) — to show representative ECGs from 8 different patients with this syndrome.
  • I present 2 additional cases of deWinter T waves in ECG Blog #53 and Blog #183.
  • The clinical significance of recognizing deWinter T waves in a patient with chest pain — is that this ECG finding tells you there is subtotal (if not completeLAD (Left Anterior Descending) coronary artery occlusion — with need for prompt cath and acute reperfusion.
  • NOTE: It is EASY to see how the very tall and rapidly-ascending T waves in leads V3 and V4 of Figure-1 might be interpreted as consisent with deWinter T waves. However, there are a number of reasons why I thought it unlikely for the LAD to be the "culprit" artery in today's case.


Figure-2: The deWinter T Wave Pattern (as first described by Robbert J. de Winter et al in N Engl J Med 359:2071-2073, 2008). ECGs for the 8 patients shown here were obtained between 26 and 141 minutes after the onset of symptoms.


PEARL #3: The KEY point in favor of posterior infarction rather than deWinter T waves lies with the History — as the patient in today's case had been having chest discomfort for weeks!

  • ECG findings in the limb leads of Figure-1 are clearly consistent with inferior infarction. The relatively large size of the inferior Q waves (considering how tiny QRS amplitude is in these leads) — together with surprisingly deep inferior lead T wave inversion suggests that spontaneous reperfusion has already occurred. This usually takes some time (ie, it is less likely that the inferior infarction occurred during the past few hours).
  • Application of the Mirror Test, as shown in Figure-3 for leads V2, V3 and V4 reveals the characteristic picture of recent (but not acute) infarction with reperfusion T waves. That is, the mirror-image of the tall, rapidly-rising and peaked T waves seen in anterior leads corresponds to what would be deep, symmetric T wave inversion over the posterior wall of the left ventricle (Application of the Mirror Test is illustrated in ECG Blog #193 and Blog #80).
  • KEY Point: It is only because some time has passed since the onset of the acute event in today's case — that confusion arose between impending LAD occlusion (ie, the question of deWinter T waves)vsrecent (but not acute) RCA (Right Coronary Artery) or LCx (Left Circumflex) occlusion, now with reperfusion T waves in the inferior and anterior leads. The history of acute infero-postero MI is much less likely to be confused with deWinter T waves — because very tall, rapidly-rising T waves are unlikely to be seen so soon in the anterior leads when posterior infarction has just occurred (See cases in ECG Blog #80 and Blog #193).

 

PEARL #4: Take another look at the 8 examples of deWinter T waves that are shown in Figure-2. Note that with the possible exception of the 4th example — the T wave upstroke is rapid!

  • A slight "shelf" (ie, horizontal segment) to the initial J-point ST depression is seen in the 4th example — but the duration of this "shelf" in those leads with giant T waves (leads V2, V3, V4) is short.
  • Compare the shape of the depressed ST segments in leads V3, V4 and V5 of Figure-3. Isn't there a longer-lasting ST segment "shelf" (horizontal segment) than we saw for the 8 examples of deWinter T waves in Figure-2? 
  • KEY Point: The T wave upslope with the deWinter pattern tends to be much steeper than the ECG picture of posterior MI.

 

PEARL #5: R wave progression tends to be poor with impending anterior MI from acute LAD occlusion. Note the generally reduced r wave amplitude in the anterior leads for the 8 examples of deWinter T waves shown in Figure-2. Frank anterior Q waves are even seen in the 6th example.

  • In contrast — a predominant R wave is seen in lead V1 of Figure-3, followed by an increase in R wave amplitude in leads V2 and V3. As noted earlier — this predominant R wave in lead V1 in the setting of recent inferior infarction strongly suggests associated posterior MI. We would not expect these prominent anterior R waves with deWinter T waves of impending anterior infarction.

 

PEARL #6: The amount of ST depression with posterior MI tends to be maximal in lead V2 — and/or lead V3 — and/or lead V4. These are precisely the leads in Figure-3 that manifest the greatest amount of "shelf-like" ST depression.


Figure-3: I've applied the Mirror Test to leads V2, V3 and V4 from Figure-1 (See text).

 

Case CONCLUSION:

Cardiac cath was performed on the patient in today's case — and revealed a mid-RCA (Right Coronary Artery) lesion, consistent with an infero-postero MI that had probably occurred days-to-a-week-or-so previously.

  • This cath finding is perfectly consistent with the ECG picture in Figure-3 — in which the most prominent finding is the reperfusion T waves that are negative in the inferior leads — and very tall and peaked in the chest leads.

  

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Acknowledgment: My appreciation to Ingram Lai (from Taiwan) for the case and this tracing.

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Related ECG Blog Posts to Today’s Case: 

  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation (outlined in Figures-2 and -3, and the subject of Audio Pearl MP-23 in Blog #205).

  • ECG Blog #193 — illustrates use of the Mirror Test to facilitate recognition of acute Posterior MI. This blog post reviews the basics for predicting the "culprit" artery. NOTE: The Audio Pearl reviews the concept of why the term "OMI" ( = Occlusion-based MI) should replace the more familiar term STEMI. 
  • ECG Blog #80 — Reviews determination of the "culprit" artery and application of the Mirror Test for recognition of acute Posterior MI.
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  • ECG Blog #248 — Reviews a case that illustrates Causes of a Tall R Wave in Lead V1 (with the Audio Pearl in this post devoted to this subject).
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  • ECG Blog #184 — illustrates the "magical" mirror-image opposite relationship with acute ischemia between lead III and lead aVL (featured in Audio Pearl #2 in this blog post).
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  • ECG Blog #262 — Reviews a case of recent acute Infero-Postero MI with group beating from Wenckebach conduction and Low Voltage (with a list of the causes of Low Voltage).
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  • 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 — Reviews another case of deWinter T Waves.




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