Saturday, May 23, 2015

ECG Blog #112 (Sinus Rhythm – Lead II – Nonspecific ST-T Wave Abnormalities

The ECG in Figure-1 was obtained from a 43-year old man who presented to his primary care clinician because he “wasn’t feeling well”. His symptoms suggested an influenza-like syndrome. The ECG was ordered because of some associated and atypical chest discomfort.
  • Are you concerned about the ST-T wave changes on this tracing?
  • Any other findings of note?
Figure-1: 12-lead ECG and lead II rhythm strip obtained from a 43-year old man with influenza-like illness and atypical chest pain. Are you concerned about ST-T wave changes on this tracing? Other findings of note? NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window.
ANSWER: The reason we selected this tracing was not because of the ST-T wave changes. Instead, our focus was on the cardiac rhythm. If you did not appreciate anything unusual about the rhythm Take a 2nd look ... 
The rhythm is fairly regular at a rate slightly less than 100/minute. There is no P wave visible in lead II. We say this based not only on the 3 beats shown for lead II within the 12-lead ECG, but also on complete lack of atrial activity on any of the 15 beats seen in the long lead II rhythm strip at the bottom of the tracing. Therefore — this is not a sinus rhythm.
  • Atrial activity is seen in several other limb leads. That is, small-but-definitely-present upright P waves with a fixed PR interval are seen preceding each QRS in leads I and aVL — and, a small negative P wave precedes each QRS in lead III. Thus, this is a low atrial rhythm.
  • Tiny upright P waves are also seen in lead V1 and V2. These would be easy to overlook were it not for the presence of definite atrial activity in leads I,III and aVL.
Regarding the other findings on this tracing:
Intervals: Both QRS duration and the QT interval are normal. Since the rhythm is not sinus — we cannot assess the PR interval (other than to say that it does not appear to be prolonged).
  • Axis: Normal (approximately +50 degrees).
  • Chamber Enlargement: None.
  • Q-R-S-T Changes: No consistent Q waves are seen. Transition may occur slightly early (the QRS complex is equiphasic by lead V2 — and definitely positive by lead V3). There is nonspecific ST-T wave flattening in multiple leads — but nothing that appears to be acute.
IMPRESSION: As stated — the reason this ECG was obtained was the patient’s description of atypical chest discomfort. While ultimate decision-making depends on full clinical assessment of the patient — this ECG should be reassuring in that at least there are no acute changes. The presence of nonspecific ST-T wave abnormalities and a non-sinus (low atrial) rhythm are not pathologic per se — and may simply reflect that the patient was not feeling well with an influenza-like illness. Whether or not to repeat the ECG if the patient’s clinical course is otherwise uneventful — is a determination that can be decided in follow-up.
KEY Point: Assuming there is no dextrocardia or lead misplacement — IF there is no upright P wave in lead II — then the rhythm is not sinus! For this reason, the very 1st Thing To Do when assessing any 12-lead ECG or rhythm strip — is to look at lead II to see if an upright P wave is (or is not) present. In our experience, failure to do so accounts for the main reason that non-sinus rhythms are sometimes overlooked ...
  • Although lead II is typically the best lead for visualizing P waves there are times when other leads may visualize atrial activity not seen in lead II. In general anatomic proximity of lead V1 (overlying the atria) makes this lead the 2nd-best for visualizing atrial activity. This is especially true when the rhythm is non-sinus. Leads III and aVR are other leads on a 12-lead tracing that often pick up non-sinus activity that might not be seen in lead II. Bottom Line: If no atrial activity is seen in lead II Be sure to survey each of the other 11 leads before concluding that no atrial activity is present.

Sunday, May 10, 2015

ECG Blog #111 (Addendum to ECG Video-9) - How to Distinguish between Escape vs Conduction?

NOTE: This is an advanced ECG post that supplements my ECG Video-9. The essential concepts to master were presented in the Video. But for those who want more — this post looks closer at how to tell which beats in a tracing with 2nd-dgree (but not complete) AV block are likely to be conducted vs which beats represent a non-conducting escape focus. Spoiler Alert: What follows assumes you have already seen our ECG Video-9. We start with the Answer to that case — and then explore in more detail how we got there ...
In ECG Blog #110 ( = ECG Video-9) We presented the case of a 75-year old woman with syncope and dyspnea who presented to the ED (Emergency Department) with the simultaneously-recorded 3-lead rhythm strip shown in Figure-1. Although health care providers on the scene initially diagnosed this rhythm as complete AV block — there is ample evidence against this diagnosis!
  • QUESTION: Can you think of at least 3 reasons why we know that beats #1-thru-5 represent an escape focus, and — that beats #6-thru-9 in Figure-1 are being conducted?
Figure-1: Simultaneously-recorded 3-lead rhythm strip from a 75-year old woman with syncope. Red arrows in lead II highlight regular atrial activity. Although there is AV dissociation early on — this rhythm is not complete AV block. Can you think of at least 3 reasons why we know that beats #1-thru-5 represent an escape focus, and  that beats #6-thru-9 are being conducted? NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window.
ANSWER: The KEY to interpreting this rhythm strip (and to developing the complex laddergram that we work through in ECG Video-9) — lies with recognizing that the QRS complexes for beats #1-thru-5 represent a ventricular escape focus. To arrive at this conclusion — We approach this arrhythmia in the same way we approach any complex rhythm = Begin with what you know!
  • NOTE: Use of calipers is of invaluable assistance for interpreting this rhythm strip! To facilitate discussion — We substitute Figure-2 for Figure-1, in which we add in our caliper measurements of critical intervals.
Figure-2: Our caliper measurements of key intervals have been added. How do these numbers support our contention that beats #1-thru-5 represent an escape focus? (See text).
Why then do we say that beats #1-thru-5 represent a ventricular escape focus?
  • Starting with what we know the constant PR interval (of 195 msec.) for the last 4 beats on this tracing confirms sinus conduction. It should be emphasized that there is 2:1 AV block during these last 4 beats — but the fact that the previously variable PR interval suddenly becomes constant ( = 0.195 second) tells us beyond doubt that sinus conduction is at least intermittently occurring.
  • Note that the QRS complex manifests an rS configuration in lead V1 (small initial positive r wave; deep negative S wave) for these 4 sinus-conducted beats. In contrast — each of the preceding 5 beats manifest a multiphasic (rsR’s’) complex in lead V1. Since there is no apparent reason for aberrant conduction during beats #1-thru-5 (since the ventricular rate isn’t overly fast) — the most logical reason for this change in QRS morphology is the presence of an escape focus for beats #1-thru-5 (especially since QRS morphology changes beginning with beat #6, which is the first of 4 consecutive beats to conduct with the constant PR interval of 195 msec.).
  • Finally — the R-R interval shortens prior to beat #6. In our experience, in the presence of AV dissociation — one of the most helpful clues that intermittent conduction is occurring — is recognition of unexpected shortening in the R-R interval. This is admittedly subtle in Figure-2. Nevertheless, preceding R-R intervals for the first 5 beats on the tracing are between 1.22-to-1.24 second — whereas the R-R interval preceding the change in QRS morphology (that begins with beat #6) = 1.20 second. Additional slight shortening of the R-R interval is seen preceding the next 3 sinus-conducted beats. Admittedly, underlying subtle variation in the rate of both the escape rhythm and the sinus rate complicate assessment of R-R interval duration — but the fact that all sinus-conducted beats (#6-thru-9) manifest a shorter R-R interval than all non-conducted beats clearly supports our contention that beats #1-thru-5 represent an escape focus.
  • We surmise that the escape focus is below the AV node — because QRS morphology of beats #1-thru-5 significantly differs from QRS morphology for the 4 conducted beats (#6-thru-9). That said — the fact that QRS duration of these 5 escape beats (#1-thru-5) is no more than minimally widened suggests that the site of escape is still within the conduction system — probably within the bundle branch sysem.
CONCLUSION: Full discussion of this case (with illustrative laddergram) is presented in our ECG Video-9. While recognition of all subtleties described above is clearly not needed to correctly interpret this rhythm — Our hope is that these more advanced concepts provide additional insight for optimal assessment of the AV blocks.
  • NOTE: For full review on the Basics of AV Blocks  Please check out our 58-minute ECG Video-8 .
Acknowledgment — My appreciation to the following individual:
  • Dr. Jenda Stros (Liberec, Czech Republic) — for providing me with the case for my ECG Blogs #110, 111, and for  Video-Blog #9.

Thursday, May 7, 2015

ECG Blog #110 (ECG Video-Blog-9) - Is AV Block Complete? / Laddergram Primer

     This is the 9th installment of my ECG Video Blog. This 23-minute video features a case for distinguishing between Complete AV Block vs AV Dissociation. Our discussion features how to draw the laddergram for this case. Your Feedback is welcome on these ECG Video-Blogs!
NOTE: There are advantages to using a video format format. These include:
  • Ability to illustrate concepts not done full justice by the written word.
  • Greater dispersion of my content through Google & YouTube. This material is free for anyone to use.
LINKS to my ECG Video-Blog installments:
  • ECG Video-Blog #1-Revised (= Blog #95) — Is there AV Block?
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  • ECG Video-Blog #2 (= Blog #96) — Bundle Branch Blocks
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  • ECG Video-Blog #3 (Blog #97— SVT with marked ST Depression
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  • ECG Video-Blog #4 (= Blog #98) — Clinical Arrhythmia Mgmt (Part I )
  • ECG Video-Blog #5 (Blog #99) — Clinical Arrhythmia Mgmt (Part 2 )
  • ECG Video-Blog #6 (Blog #100) — Clinical Arrhythmia Mgmt (Part 3 )
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  • ECG Video-Blog #7 (= Blog #101) — Wide Tachycardia + Chest Pain
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  • ECG Video-Blog #8 ( = Blog #105) — Basics of AV Block
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  •    ECG Video-Blog #9 ( = Blog #110) — Complete AV Block? / Laddergrams
  •     Addendum to Video-9 ( ECG Blog #111) — Review of Key Concepts
  •     Click Here for Timed Contents to Video-Blog #9!
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  • ECG Video-Blogs #10,11,12 ( Blog #113) — Rhythm Diagnosis Basics
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  • ECG Video-Blog #13 ( = Blog #116) — Essentials of Axis / Hemiblocks
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  • ECG Video-Blog #14 ( = Blog #117) — Brugada Syndrome
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  • ECG Video-Blog #15 ( = Blog #118) — QRST Changes
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  • ECG Video-Blog #16 ( = Blog #120) — Giant T Waves
      Acknowledgment — My appreciation to the following individual:
      • Dr. Jenda Stros (Liberec, Czech Republic) — for providing me with the case for ECG Video-Blog #9.
      The patient is a 75-year old woman who presented to the Emergency Department with syncope and shortness of breath. A diagnosis of Complete (3rd-Degree) AV Block was made from the ECG shown in Figure-1. The patient was hemodynamically stable at the time this tracing was recorded.
      • Is the rhythm in Figure-1 complete AV Block?
      • Explain your answer ...
      Figure-1: Simultaneously-recorded 3-lead rhythm strip obtained from a 75 year old woman with syncope and shortness of breath. Is this complete AV Block? Explain WHY this is (or might not be) complete AV Block. NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window.
      GT–  on YouTube to view this ECG Video (23 minutes).
      • Click Here  — for a Timed CONTENTS of Video-Blog #9.
      • Please check out our ECG Blog-111 for an Addendum to ECG Video #9.
      • Please also check out my ECG Video Blog page on Google. The link is easy to remember = -
      NOTE: For a Power Point Show (.ppsx) version of my Video Blogs - CLICK HERE. This folder will contain links to download a .ppsx version that allows faster viewing:
        • Download the .ppsx to your computer desktop.
        • The PPT show is without automatic sound. YOU activate only the Audio clips you want.
        • Hover your mouse over the highlighted Audio. You may play and/or pause if/as you like.
        • Feel free to use this .ppsx for teaching with my blessings!