Tuesday, March 1, 2011

ECG Blog #16 — 23 yo Woman; Atypical Chest Pain

QUESTION: The ECG in Figure-1 was ordered on a 23 year old woman who was seen in the office a day earlier. No history was given.  No prior tracing was available for comparison.
  • How would you interpret this ECG?
  • Clinically — What would you do if you were reading this ECG the day after without the benefit of any history to go on?

Figure-1: ECG from a 23 yo woman with atypical chest pain.

INTERPRETATION: The rhythm is sinus at a rate just under 100/minute. All intervals (PR, QRS, QT) are normal. The mean QRS axis is normal (at +75 degrees). There is no chamber enlargement.
  • Q-R-S-T Changes:  — There is definite baseline wander in several leads on this tracing (most notably in leads III, aVL, aVF, and lead V2). There appears to be a tiny q wave in lead III. Transition is normal (occurs between leads V2-to-V3).  There is subtle but real ST segment elevation in a number of leads.

CLINICAL IMPRESSION: Although one might want to be "lulled" into a sense of security by the young age of this patient — this is not a normal tracing in a 23 year old woman. The ST segment elevation is real (Figure-2).  Clearly — the baseline wander (especially in lead V2) makes assessment of ST segment position difficult.  That said — one is struck by the straight takeoff with almost hyperacute T waves and suggestion of subtle ST segment elevation in many of the leads on this tracing.

Figure-2Blow-up of the precordial leads from Figure 1. Despite baseline wander (blue double arrow in V2) — the J-point is elevated above the PR segment baseline in leads V2-thru-V5 (short red lines).

COMMENT: Given the age of this patient, the diffuse nature of the ST-T wave change, and the lack of any reciprocal ST depression — myocardial infarction is unlikely. However, young adults do get acute pericarditis — and the constellation of a relatively rapid heart rate with subtle but diffuse ST elevation and morphology seen here is certainly consistent with a diagnosis of acute pericarditis. We felt a need to review the chart and contact the treating physician. Turns out the history was of atypical chest pain of relatively recent onset that was initially attributed to a musculoskeletal cause (with the patient being sent home on a short course of NSAID therapy). In view of this history — a more likely diagnosis was acute pericarditis, with our revised plan for more careful follow-up, repeat ECG in 1-2 weeks, and to continue the course of NSAIDS (appropriate for both musculoskeletal pain and pericarditis).
  • There are many causes of acute pericarditis. These include cancer (metastasis); viral and bacterial causes; autoimmune disorders; associated myocarditis; drugs; radiation pericarditis; trauma; post-MI; tuberculosis; uremia; and “idiopathic” when no cause can be found. 
  • By far — the most likely etiology in a previously healthy young adult is a viral disorder. Most of the time — history, physical exam and the clinical setting will suggest the probable etiology.

ECG Recognition:  Pericarditis is often a difficult clinical entity to detect — especially when there is no preceding viral illness, no rub is heard, and the entity is not actively considered. The ECG can be helpful in diagnosis. Typically — there are 4 Stages to Acute Pericarditis, which we simplify as follows (Figure-3):
  • Stage I -— everything is "up" (ST elevation is seen in almost all leads).
  • Stage II — transition ( = "pseudonormalization" ).
  • Stage III — everything is "down" (inverted T waves).
  • Stage IV — normalization.

Figure-3 — The 4 Stages of Acute Pericarditis.

ST Segment Elevation: Figure-4 shows a schematic example of Stage I Acute Pericarditis. Note how diffuse the ST segment elevation is in Stage I ("everything up" stage) - being seen in virtually all leads (except the "far away" leads = blue shaded leads III, aVR, and V1).
  • ST-T wave morphology with acute pericarditis may resemble that seen with early repolarization — in that the ST segment tends to manifest an upward concavity (“smiley” configuration) rather than the coved (downward convexity) more commonly seen with acute MI. 
  • ST elevation with acute pericarditis is more generalized than that usually seen with early repolarization (that tends to be localized to one or two lead areas). 
  • J-point notching is characteristically seen in one or more leads with early repolarization — though overlap in the ECG picture between acute pericarditis and early repolarization may certainly be seen (since after all — acute viral pericarditis is commonly seen in a previously healthy young adult population who may develop this disorder superimposed on a baseline ECG showing early repolarization changes …). Look for tachycardia — a history of pleuritic-type chest pain worse on recumbency — listen carefully for pericardial friction rub — and inquire about recent viral illness. 
  • The ST elevation seen with acute MI differs from the picture of acute pericarditis in several ways: i) it is more localized — with reciprocal ST depression in other areas of the heart; ii) Q waves may be seen (absent from pericarditis, with possible exception of baseline small septal q waves); iii) leads II and III tend to look similar with acute MI (inferior changes) — vs — with acute pericarditis, leads I and II tend to look more similar (See Figure 4); and iv) the associated history will be very different for the two entities. 
  • NOTE: ST elevation (and PR segment depression) is typically absent with acute pericarditis from uremia (since the diffuse ECG changes of pericarditis are attributable to acute epicardial inflammation which is not a feature of pericarditis from uremia).

Figure-4 — Schematic example of Stage I Acute Pericarditis.

PR Segment Depression: In addition to the diffuse ST segment elevation seen in Figure-4PR segment depression is also seen.
  • PR segment depression — may be a subtle sign that supports the diagnosis of acute pericarditis. It is not always seen. It may be seen in some leads, but not in others. Close inspection of Figure 4 shows PR segment depression present in leads I, II, V2, and V3 — but not in aVL,aVF; V4,V5,V6 (You may want to click on Figure-4 to enlarge the tracing).
  • We emphasize that PR depression may be subtle — although it will be seen in at least some leads in many (not all) cases of acute pericarditis IF it is looked for. PR depression is helpful when seen — though its absence does not rule out the diagnosis ...
  • We do not seen PR depression in Figure-1 for the 23-year-old woman in this case ...
  • Acute pericarditis is one of those conditions in which we pay special attention to lead aVR. This most distant recording electrode often manifests the opposite ST/PR segment picture of most other leads (Note PR segment elevation and ST depression in lead aVR for Figure-4).
  • A final caveat regarding PR segment depression is that it may occasionally be seen in normal subjects ... Thus, both sensitivity and specificity of PR depression are imperfect indicators of acute pericarditis. That said — this sign may be very helpful IF found in selected cases when symptomatic patients present with subtle ECG findings.

To clarify how to recognize PR depression — we add a blow-up of 4 leads taken from another patient with acute pericarditis (Figure-5). Note subtle but real PR segment depression in leads II, III, and aVF (as judged with respect to the R-P baseline).

Figure 5 — 4-lead blow-up taken from a patient with acute pericarditis. There is PR segment depression in leads II,III,aVF — as judged with respect to the R-P baseline (arrow in lead II shows the PR is below this baseline — while the ST segment is above it).

CONCLUSION (Bottom Line):  A history is needed for accurate ECG interpretation. If the 23-year-old woman presented in this case in question asymptomatic — then the tracing seen in Figure-1 could conceivably represent a normal repolarization variant. Knowing that this young woman instead had atypical chest pain of recent onset makes it much more likely that the constellation of ECG findings seen represents acute pericarditis. Given transition between the "everything up" ST elevation stage (Stage I in Figure-3) — and the "everything down" T wave inversion stage (Stage III) — it may be that another reason for the subtle findings in Figure-1 is that this tracing caught the patient in transition (Stage II) between diffuse ST elevation returning to the baseline on its way to evolving toward diffuse T wave inversion. The findings of acute pericarditis may indeed be subtle.

Final CAVEAT (Clinical Pearl ):  A common differential diagnosis is between acute pericarditis vs ACS (Acute Coronary Syndrome). Keep in mind that in practice — ACS is far more common than acute pericarditis. Despite this clinical reality — acute pericarditis tends to be greatly overdiagnosed ... The onus of proof is on US to rule out ACS as the cause of ST elevation, rather than the other way around. BOTTOM LINE: It's best not to diagnose acute pericarditis until you have ruled out ACS!

  — See also ECG Blog Review #12 — and — this pdf from Section 12.0 of ECG-2014-ePub

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