Friday, November 22, 2013

ECG Interpretation Review #79 (Normal Q Wave – T Wave Inversion – Ischemia - Infarction)

     You are told that the limb lead sequence shown in Figure-1 was obtained from a middle-aged adult. You note a Q wave and symmetric T wave inversion in lead III.
  • Has this patient had an inferior infarction?
  • Is T wave appearance in these 6 limb leads suggestive of ischemia?
Figure-1: Limb lead sequence from a middle-aged adult. Is lead III appearance suggestive of ischemia/infarction? (Figure reproduced from ECG-2014-ePub). NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window (See text).
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Interpretation of Figure 1:
Clinical ECG interpretation is dependent on history. It is essential to appreciate that ECG findings that might prompt concern in a patient with new-onset chest discomfort may not necessarily be interpreted as abnormal in a non-acute setting in an otherwise healthy individual. Such is the case for the 6 limb lead sequence shown in Figure-1. We note the following:
  • A Q wave is seen in lead III of Figure-1. Technically — this is a QS complex, since there is no R wave. Although this Q wave is not particularly deep (it is only 2mm) — given lack of any R wave, this Q wave (QS complex) portends the same clinical implications as would a larger or wider Q wave. That said — Q waves are not seen in the other 2 inferior leads (leads II,aVF).
  • There is fairly deep symmetric T wave inversion in lead III (especially in view of the small amplitude for the QRS complex in this lead). IF this finding was noted in a patient with new-onset chest discomfort — We would clearly be concerned about acute ischemia. That said — there is no more than nonspecific ST-T wave flattening in lead aVF and no ST-T wave abnormality in the other inferior lead (= lead II ).
  • Clinical Note: The T wave vector often follows fairly close behind the QRS vector. As a result — isolated T wave inversion that often occurs in leads III, aVL or aVF is clearly less likely to be ischemic IF the QRS complex is also predominantly negative in the lead that manifests T wave inversion. This is the case for lead III in Figure-1.
Impression: We would note the following on our interpretation: “Q wave with T inversion in lead III; nonspecific ST-T wave flattening in aVF; Suggest clinical correlation”.
  • That said — All bets would be off IF this patient had new-onset chest discomfort, since absence of abnormality in lead II does not exclude the possibility of acute ischemia/infarction. But IF this patient was asymptomatic (especially if a prior tracing was available and showed similar findings) — We would strongly suspect that the ECG appearance in lead III of Figure-1 was not indicative of ischemia/infarction.
  • Take-Home” Point: Most of the time when Q waves/T inversion reflects ischemia or infarction — neighboring leads will show similar changes.
Figure-2: Normal Q Waves; Normal T Inversion
Among the most challenging tasks for the ECG interpreter — is deciding what is “normal” vs “abnormal”. Our purpose in devising Figure-2 — is to facilitate remembering when the finding of even a large Q wave or deep T wave inversion may be normal.
  • 5 of the leads on a standard 12-lead ECG (= leads III-aVR-aVL-aVF-V1) — may normally display even moderate-to-large Q waves and/or T wave inversion in healthy adults who do not have heart disease.
  • Thinking of a “reverse Z” (à la Zorro) — may help to recall which leads these are (Figure-2).
Figure-2: Leads that may normally manifest T wave inversion or Q waves. Recall of these leads is facilitated by thinking of a reverse “Z”. (Figure reproduced from ECG-2014-ePub).
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KEY Points: Traditionally — the finding of a deep and wide Q wave is thought to be a marker of myocardial infarction. Other pathologic reasons for Q waves exist — including cardiomyopathy (scarring/fibrosis); conduction defects and WPW. It is well to be aware of instances when Q waves (and associated T wave inversion) may be a normal finding.
  • Normal septal q waves — are common. Septal q waves are small and narrow. They arise because the first part of the ventricles to normally depolarize is the left side of the septum. As a result — left-sided leads see the initial depolarization vector as moving away from the left as the septum depolarizes from left-to-right. This accounts for the normal small q wave that may commonly be seen in one or more of the lateral leads (= leads I-aVL-V4-V5-V6) in asymptomatic individuals without heart disease. The reason we do not include normal septal q waves in Figure-2 is because their small and narrow dimensions makes it obvious that such q waves are unlikely to be pathologic.
  • Lead aVR — is normally all negative (negative P wave, QRS and T wave as seen in Figure-2). Global negativity for lead aVR is logical given the remote right-sided location of this unipolar lead (the depolarization vector continually moves away from right-sided lead aVR under normal circumstances).
  • Lead V1 in adults — typically shows a QS or rS complex and T wave inversion (Figure-2). A QS complex may normally still be seen in lead V2 without this necessarily meaning there has been prior septal infarction. However, by lead V3 — at least some r wave should be seen under normal circumstances. Regarding T wave appearance in lead V1 — the T should normally be upright by lead V2 in adults. Persistent T wave inversion in anterior leads should prompt consideration of ischemia. NOTE: The situation is different in children — for whom anterior T wave inversion up to lead V3 (or even V4) may reflect a normal juvenile T wave pattern.
  • Leads III, aVL, aVF (as in Figure-2) — may all normally show T wave inversion and/or an isolated Q wave that is not the result of ischemia or infarction — provided that these findings are not also seen in neighboring leads.
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Applying Figure-2: Returning to Figure-1 — We see an isolated Q wave and T inversion in lead III. This may be a normal finding — especially IF: i) it is isolated to this single inferior lead (as it is in Figure-1); ii) the QRS complex in lead III is predominantly negative in the lead which shows T inversion; and iii) the patient is not having new-onset chest pain.
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— For more information — GO TO 
  • CLICK HERE  — to download a pdf of Section 09.0 on ST-T Wave Changes (excerpted from ECG-2014-ePub).
  • For additional Review on the Basics of assessing for Q-R-S-T Changes — lease see our ECG Blog #94 (Basic Concepts #7 ) -
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  • Please check out my Comment 1183 on the ECG Guru for additional illustration of how isolated findings in one of the above limb leads is generally "benign". 

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Monday, November 11, 2013

ECG Interpretation Review #78 (PACs – Atrial Bigeminy – Aberrancy – Blocked PAC – AV Block)


The simultaneously recorded 2-lead rhythm strip shown below in Figure 1 was obtained from a young adult feeling “skips”.
  • What is the rhythm?
  • Is there intermittent AV block?
Figure 1: ECG from a young adult with “skips”. NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window (See text).
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Interpretation of Figure 1:
The challenge in this tracing is to find 2 normal beats in a row. The only place where this seems to occur is at the very end of the rhythm strip for beats #14,15. This tells us that the underlying rhythm is sinus tachycardia.
  • Note how smooth the T wave is in both lead I and lead II for beats #14 and 15.
  • Careful inspection of all T waves in both leads of this tracing reveals slight-but-real notching in almost all complexes. This is subtle. Be sure to click on the figure to enlarge the rhythm strip. Look first at lead I. Other than the T wave for beats # 8, 14 and 15 — there is a tiny but unmistakable notch in all other T waves.
  • Each notch represents a PAC.
  • Sinus P waves on this tracing are beats #1,3,4,5,7,9,10,11,12,14 and 15.
  • The rhythm is atrial bigeminy — in that a PAC occurs in the T wave after each sinus beat (red arrows in Figure 2).
Figure-2: Red arrows in the T wave of sinus beats indicates PACs. The rhythm is atrial bigeminy. Some PACs are conducted with aberration — others are blocked (See text).
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Looking Closer: The KEY to interpreting this rhythm is to appreciate the overall pattern. Once you identify 2 normal beats in a row (ie, beats #14,15) — you can determine what the “normal T wave” should look like (= smooth without any notching).
  • Beat #1 is sinus.
  • Beat #2 occurs early. The unmistakable notch in the T wave of beat #1 indicates that this is a PAC (Premature Atrial Contraction) and not a premature ventricular beat.
  • The reason for the different and wider QRS morphology of beat #2 is that this PAC is conducted with aberration. Most aberrant beats conduct with a recognizable pattern of some form of bundle branch block or hemiblock, due to refractoriness of some portion of the conduction system. The deep and wide S wave of beat #2 in lead I with qR pattern in lead II suggests RBBB/LPHB aberration.
  • Beat #3 is sinus.
  • Note notching in the T wave of beat #3. This is the result of a blocked PAC (the PAC occurs so early in the refractory period that the entire conduction system is refractory, and the PAC is non conducted).
  • Beat #4 is sinus. Another blocked PAC is hiding in (and notching) the T wave of beat #4.
  • Beat #5 is sinus.
  • Beat #6 is an aberrantly conducted PAC.
  • Beat #7 is sinus.
  • Beat #8 is an aberrantly conducted PAC.
  • Beats #9,10,11 and 12 are sinus. Blocked PACs notch the T waves of beats #9,10,11.
  • The PAC notching the T wave of beat #12 is conducted with aberrancy (= beat #13).
  • Beats #14 and 15 are the only two sinus beats seen to occur in a row on this tracing.
Bottom Line: The rhythm is sinus tachycardia with atrial bigeminy. PACs are either blocked or conducted with aberration. There is no AV block. Given that the patient is a young adult feeling “skips” — one should inquire about potential causative factors (ie, caffeine or other stimulants) that may be causative.
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  • Acknowledgement: My appreciation to Simon Mortensen (of Odense, Denmark) for allowing me to use this case.
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- For more information  GO TO:
  • See ECG Blog #14 — ECG Blog #15 — and — ECG Blog #33 for review of aberrant conduction.
  • CLICK HERE  — to download a pdf on Aberrant Conduction from Section 19.0 (in our ACS-2013-ePub).
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Friday, November 1, 2013

Follow-up Note- from Dr. Ken Grauer

NOTE: I regret to say that my e-mail has been hacked. Please disregard any message or e-mail you may have received asking for money. I never went to the Ukraine. I am fine. I have filed a Police report. Very SORRY for the inconvenience! My ECG Interpretation Blog should now once again be functioning normally. Thank you for your understanding. - Ken Grauer, MD (ekgpress@mac.com)
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