I was sent the ECG in Figure-1 — but without the benefit of any history. I was asked for my opinion as to whether this tracing represented an acute STEMI?
QUESTIONS:
- How should I answer?
- Is this "new" or "old" Wellens?
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| Figure-1: The initial ECG in today's case — which was sent to me without the benefit of any history. (To improve visualization — I've digitized the original ECG using PMcardio). |
MY Answer:
Even without knowing the history — the ECG in Figure-1 is clearly of concern:
- PEARL #1: Although there is often a tendency to skip the basics, and go straight to the obvious findings (which are seen here in the inferior leads!) — I prefer to always take a brief look first at the rhythm. (For this — I favor the Ps,Qs,3R Approach for systematic rhythm interpretation = ECG Blog #185).
- To Emphasize: There is no need to spend more than a couple of seconds in this initial glance at the rhythm — and there is no need to come up with a definitive rhythm diagnosis at this point in time!
- Instead — You simply want to find out: i) What is the approximate Rate of the rhythm? (ie, Is the patient likely to be stable at this heart rate?); — and, ii) Is the rhythm sinus or something else?).
Is the Rhythm Sinus?
If I were charged with treating the patient in today’s case — I’d immediately go to the bedside to determine a brief history, and verify that this patient was hemodynamically stable with the rhythm shown in Figure-1. Since I was not yet provided with this information — I assumed the patient was stable enough for me to proceed with my interpretation of today’s initial ECG:
- PEARL #2: The rhythm is not sinus — because the P wave in lead II is not upright! ( = YELLOW arrows in Figure-2). Assuming there is no lead reversal — the finding of a negative P wave in lead II indicates either a junctional or low atrial rhythm.
- Note that these negative P waves in lead II of Figure-2 do manifest a constant PR interval, such that they are conducting (because these P waves are Related by a fixed PR interval to neighboring QRS complexes).
- Note also that no P waves are seen throughout the long lead V1 rhythm strip at the bottom of the tracing. However, there is a negative P wave seen in simultaneously-recorded lead V3 (YELLOW arrow in that lead). Thus the reason no P wave is seen in lead V1 — is that morphology of the retrograde P wave in lead V1 must be isoelectric to the baseline.
Otherwise ...
- The QRS complex is narrow ( = not more than half a large box in duration) — so the rhythm is supraventricular.
- The ventricular rhythm is Regular — at a Rate of ~50/minute (ie, R-R interval a tiny bit over 6 large boxes in duration).
- Bottom Line: Given lack of a visible P wave in lead V1 + the narrow QRS + the slow ventricular rate of ~50/minute — this appears to be a junctional escape rhythm.
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| Figure-2: Negative P waves in the inferior leads indicate this is a non-sinus rhythm. The narrow QRS, slow rate and lack of visible atrial activity in lead V1 suggest this is a junctional escape rhythm. |
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The Rest of the ECG ...
In addition to the slow junctional escape rhythm — Figure-3 highlights KEY findings in the leads of most concern:
- Extremely large Q waves are seen in leads III and aVF. This is associated with a hyperacute appearance of the ST segment that manifests considerable J-point elevation with a straightened ascending ST segment takeoff. There is fairly deep terminal T wave inversion.
- The 3rd inferior lead ( = lead II) — manifests a bizarre, fragmented QRS, with similar looking but less marked ST-T wave changes.
- Reciprocal ST-T wave changes are seen in lead aVL (within the BLUE rectangle) — in the form of a straightened and depressed ST segment (that manifests gradual downsloping, but which finishes with terminal T wave positivity).
- Lead V3 is uninterpretable due to artifact ...
- Less marked but still concerning ST-T wave findings are present in 3 additional leads. These include: i) Lead I (which is similar in shape, but with less prominent reciprocal changes compared to aVL); ii) Lead V2 (which manifests ST segment straightening with loss of the normal slight ST elevation usually seen in this lead); — and, iii) Lead V6 (with a QRS and ST-T wave similar to that seen in lead II).
Putting It All Together:
I had more questions than answers after reviewing this ECG:
- The extremely large Q waves in leads III and aVF indicate that the patient has had an inferior infarction at some point in time.
- The hyperacute-looking ST segments with ST elevation, in association with reciprocal ST depression in lead aVL — suggest an inferior MI that may be recent (or ongoing) — with the findings in leads V2 and V6 suggesting associated posterior and lateral involvement.
- The above said — the terminal T wave inversion in the inferior leads and in lead V6 + terminal T wave positivity in leads I,aVL and V2 could all represent evolving reperfusion changes of completed infarction.
- BOTTOM Line: We need some history to proceed further with our interpretation. Along the way — finding a previous ECG for comparison should prove invaluable for determining what is "new" vs "old".
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| Figure-3: I've labeled the leads of most concern. |
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The CASE Continues:
I was finally able to learn a bit more about this case.
- This ECG is from a middle-aged woman with known coronary disease, having undergone stent placement following an MI about 1 year earlier.
- She presented this time with ongoing severe CP (Chest Pain) that began ~2 hours prior to the time that ECG #1 was recorded.
- Despite the slow junctional escape rhythm — she was hemodynamically stable.
My Thoughts:
- Although with this past and present history I was still uncertain as to what was "new" vs "old" vs "new superimposed on old" — given the presence of hyperacute-looking ST-T wave changes with ST elevation and ongoing severe CP — prompt cath is needed to define the anatomy!
- PEARL #3: The slow junctional escape rhythm in Figure-3 is an additional feature that suggests a recent and/or ongoing OMI (Occlusion-associated Myocardial Infarction) may be present ==> Prompt cath is needed!
A Previous ECG is Found ...
On searching the patient's chart — a previous ECG was found. To facilitate comparison — I've placed both tracings together in Figure-4.
QUESTIONS:
- What do you learn from seeing this previous ECG?
- What is the "problem" with this previous ECG?
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| Figure-4: Comparison of the initial ECG with a previous ECG. |
ANSWERS:
Before addressing the question as to what we learn from Figure-4 — Consider this "problem" with the previous ECG:
- PEARL #4: All-too-often when I'm sent cases in which a previous ECG is provided for comparison — there is no indication as to what the clinical situation was at the time the prior tracing was recorded.
- For example, in Figure-4 — there are obvious marked abnormalities in the previous tracing. As a result, our approach as to how to interpret this comparison tracing that is now provided to us in Figure-4 may vary greatly depending on whether ECG #2 was recorded:
- During the acute phase of a previous OMI?
- Immediately after this patient received her stent ~1 year earlier?
- OR — At a routine follow-up visit after the patient had been pain-free for months?
On further review of this patient's chart — it was learned that this previous ECG was recorded around the time of her stent placement (probably shortly after stent placement in the "culprit" RCA).
- Presumably the deep Q waves in leads II,III,aVF of ECG #2 are the result of the patient's inferior MI — in which some residual ST elevation remains. In addition — there is deep symmetric T wave inversion in the inferior and lateral chest leads of this previous ECG that suggest reperfusion changes that most probably developed following stent placement.
- The overly tall T wave in lead V2 of ECG #2 — is also most probably a reperfusion change from associated posterior OMI.
KEY Point: Despite obvious abnormalities in the previous ECG — We are still able to advance our diagnosis in today's case given the clinical context that today’s patient is now presenting to the ED for acute severe CP beginning just 2 hours prior to the recording of ECG #1. My thoughts regarding Figure-4 were the following:
- The rhythm in today’s initial ECG is no longer sinus. Instead — there is a slow junctional escape rhythm at ~50/minute.
- Although the inferior Q waves are similar to those that were present in the previous ECG — there is now more ST elevation with a hyperacute appearance in each of the inferior leads (in the form of an upsloping, straightened ST segment takeoff).
- Reciprocal ST segment depression in high-lateral leads I, and especially aVL now clearly appears to be hyperacute (with ST segment straightening, prominent terminal T wave positivity, and a gently downsloping ST segment in lead aVL that reflects the mirror-image opposite picture to the ST-T wave in lead III).
- Lateral infarction is suggested by the acute ST elevation in lead V6.
- Finally — the reperfusion changes seen in the chest leads in ECG #2 have virtually resolved (ie, reduced T wave positivity in lead V2 — and resolution of T wave inversion in leads V4,V5).
Bottom Line: Given the presentation of new severe CP — comparison of today's initial ECG with the previous tracing suggests there is now acute reocclusion of the RCA — with need for prompt cath!
On reflection of this case — several points deserve emphasis:
- As helpful as finding the previous tracing was in today's case — the need for prompt cath was already established by: i) The known history of coronary disease; — ii) The presentation of new severe CP just 2 hours before ECG #1 was recorded; — and, iii) The slow junctional escape rhythm in association with limb lead changes in ECG #1 that so clearly look to be hyperacute.
- An elevated Troponin would strengthen the need for prompt cath — but an increased Troponin is not needed to know that prompt cath is indicated (Remember that the initial Troponin may be normal despite acute coronary occlusion — and waiting until Troponin eventually elevated would only incur loss of more myocardium).
- An Echo at the bedside showing a localized inferior wall motion defect would strengthen the need for prompt cath — but this too is not needed to know that prompt cath is indicated (ie, We know this patient had a previous MI — so we would not be able to know if any wall motion abnormality was new or old).
- Although Wellens' Syndrome most commonly presented with ST-T wave abnormalities in the anterior chest leads (from high-grade narrowing of the LAD) — you can see the ST-T wave abnormalities of Wellens Syndrome in any coronary distribution. That said — today's patient presents with new CP — deep Q waves and hyperacute ST elevation — all of which tell us this is not Wellens' Syndrome (See ECG Blog #350 and ECG Blog #453 — for review of the criteria for Wellens' Syndrome).
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Acknowledgment: My appreciation for the anonymous submission of today's case with these tracings.
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