Sunday, August 28, 2011

ECG Interpretation Review #28 (ST-T Wave Changes - Ischemia - RVH - RV "Strain")

Interpret the 12-lead ECG shown below in Figure 1, obtained from a patient who presented with new‑onset dyspnea.  What two clinical diagnoses should come to mind in view of the symmetric T wave inversion seen in leads V1,V2,V3 (arrows)?
Figure 1 – 12-lead ECG obtained from a patient with new-onset dyspnea. (Figure reproduced from ECG 2011 Pocket Brain – pg 40C). – NOTEEnlarge by clicking on Figures – Right-Click to open in a separate window.
INTERPRETATION:  The mechanism of the rhythm is sinus, as upright P waves with a fixed PR interval precede each of the QRS complexes in lead II.  The R-R interval varies — defining this as sinus arrhythmia.  The PR, QRS and QT intervals are normal.  There is RAD (Right Axis Deviation) of at least +100 degrees (predominantly negative S wave in lead I ).  P waves are tall, peaked and pointed in lead II (≥2.5 mm tall) — consistent with RAA (Right Atrial Abnormality).

  • QRST Changes:  There are small q waves in the inferior and lateral precordial leads.  R wave progression is normal, with transition occurring between leads V3-to-V4.  T waves are fairly deep and symmetrically inverted in V1,V2,V3 (arrows).

SUMMARY:  Sinus arrhythmia. RAD. RAA. Symmetric T wave inversion consistent with anterior ischemia and/or right ventricular “strain”. 
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IMPRESSION:  Clinical correlation is essential to the interpretation of this tracing.  Clearly, symmetric T wave inversion may reflect ischemia from coronary disease.  Determination of whether or not this reflects an acute ECG change would require comparison with one or more prior tracings.  It is important to appreciate that the constellation of findings on this tracing may also suggest RVH (Right Ventricular Hypertrophy) and/or right heart “strain”.
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ECG Diagnosis of RVH:  Detection of right ventricular enlargement in adults by ECG criteria is often exceedingly difficult.  This is because the left ventricle is normally so much larger and thicker than the right ventricle in adults — that it masks even moderate increases in right ventricular chamber size.  As a result, many patients with RVH wont be identified — IF assessment for chamber enlargement is limited to obtaining an ECG (an Echo is needed to know for sure).
            The ECG diagnosis of RVH is best thought of as a “detective diagnosis”.  Rarely will any one finding clinch the diagnosis.  Instead — the diagnosis of RVH is most often suspected when one sees a combination of the ECG findings shown in Table 1.  This is especially true when several of these findings occur in a likely clinical setting (ie, COPD, right-sided heart failure, pulmonary hypertension).
Table 1 – List of criteria that taken together suggest RVH (Figure reproduced from ECG 2011 Pocket Brain – pg 38).
ECG Diagnosis of Pulmonary Embolism:  The ECG is usually not diagnostic of pulmonary embolism (PE).  That said — there are times when ECG will suggest the diagnosis before V/Q scan or chest CT is done.  Consider PE — IF the clinical setting is “right” (ie, new-onset dyspnea – pleuritic chest pain – predisposing risk factors or previous history of PE/DVT)and – one sees some of the following ECG clues:
  • There is sinus tachycardia (usually seen with large PE, albeit clearly nonspecific for the diagnosis).
  • There are ≥2 signs of acute “right-heart” strain (ie, RAD – RAA – RBBB – tall R in V1 – deep S in V5,V6).
  • There are ST-T wave changes of RV “strain” (ST-T depression in II, III, aVF and/or V1,V2,V3).
  • There is new-onset A Fib (common with PE, but nonspecific).
  • There are nonspecific ST-T wave changes (not diagnostic).
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CLINICAL IMPRESSION:  The clinical context for the patient whose initial ECG is shown in Figure 1 is that of “new-onset dyspnea”.  We do not know if the ECG changes seen in Figure 1 are new or old.  Clearly — the anterior symmetric T wave inversion that is seen may reflect ischemia of uncertain duration.  If the RAD and RAA are not new findings — they may reflect longstanding RVH from chronic pulmonary disease.  But IF the RAD, RAA and anterior T wave inversion are all new findings occurring in association with new-onset dyspnea — then acute pulmonary embolus would have to be strongly considered.  PEARL: Anterior T wave inversion may sometimes be an important ECG clue to the possibility of acute pulmonary embolus.
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5 comments:

  1. Another PE finding, albeit a 1-in-5er is S1Q3T3. But, I'm with you: PE is primarily a clinical diagnosis! If I've got ECG signs that also point in the direction of my "clinical gestalt" all the better.

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  2. Hi Christopher. I intentionally chose not to mention the 'S1Q3T3' sign in this short column given its very limited sensitivity and specificity (at best 20% for both, as you allude to). I've spent a career looking for S1Q3T3 on patients suspected of acute PE, and don't know that I've ever seen it in this population - though I have seen S1Q3T3 on occasion in asymptomatic healthy individuals .... So given the many false positives and negatives with very low sensitivity - I don't think it a helpful ECG sign. On the other hand - there have been a number of occasions over the years when the ONLY clue suggesting acute PE in cases with atypical symptoms has been unexplained anterior T wave inversion that led to further diagnostics which confirmed the diagnosis - so good to be aware that PE may present with this sign. THANKS again for your comment Christopher!

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  3. Heart arrhythmia is a normal and common irregular heartbeat that most people will experience at least once in their lifetime and not even know it. Arrhythmia disrupts the normal pattern can cause your heart to beat too fast, too slow, or to beat in an irregular pattern.

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  4. @Kaney - I appreciate your comment - though I'm not sure I understand relevance to this tracing (which only shows sinus arrhythmia).

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  5. great interpretations, thank you for doing this. I am a medical student and it's helpful to see everything broken down.

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