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?
  • ECG Video-Blog #2 (= Blog #96) — Bundle Branch Blocks
  • ECG Video-Blog #3 (Blog #97— SVT with marked ST Depression
  • ------------------------------------------------------------
  • 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 )
  • ------------------------------------------------------------
  • ECG Video-Blog #7 (= Blog #101) — Wide Tachycardia + Chest Pain
  • ------------------------------------------------------------
  • ECG Video-Blog #8 ( = Blog #105) — Basics of AV Block
  •    ------------------------------------------------------------
  •    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!
    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!

      Sunday, April 19, 2015

      ECG Blog #109 (Interesting Tachycardia - Video)

      As a novel concept — I thought I would post this short (1.5 minute) video I edited from material provided to me by Alex Kroeze. The patient was hemodynamically stable
      Figure-1: Freeze-frame of the interesting SVT rhythm in this video. See YouTube link for additional monitoring. NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window.
      MORAL of this Video: — that artifact unfortunately often precludes accurate determination of atrial activity (therefore disguising the mechanism of tachycardias such as this one ...).
      • PACs seem to occur at the onset of the SVT (SupraVentricular Tachycardia) runs — but underlying artifact makes discerning what happens a bit elusive ...
      That said — fun to look at (to the music of Vivaldi's 4 Seasons).

      ACKNOWLEDGMENT: My appreciation goes to Alex Kroeze for allowing me to edit and post his tracings.

      Saturday, April 11, 2015

      ECG Blog #108 (Ventricular Rhythms - AIVR - VT)

      NOTE: This is the "short version" of my ECG Blog #107 — in that I only address the 3-lead rhythm strip shown below (which was Figure-3 in Blog #107)
      The simultaneously-recorded 3-lead rhythm strip shown in the Figure was obtained from a 69-year old woman with a longterm history of palpitations. Her symptoms had been increasing over recent weeks, in association with "chest tightness" and dizziness. Her prior medical history was benign  and she was hemodynamically stable at the time this tracing was recorded.
      • How would you interpret the rhythm shown in the Figure?
      • What are clinical implications of this rhythm
      Figure: Simultaneously-recorded 3-lead Rhythm Strip, obtained from a 69-year old woman with palpitations. She was hemodynamically stable at the time of this tracing. What is the rhythm? What clinical implications are associated with this rhythm? NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window.
      InterpretationThe rhythm is fairly regular — albeit with slight variation in rate.
      • The QRS complex is wide (at least 3 little boxes = ≥0.12 second in duration).
      • Normal sinus P waves are missing in lead II. Instead, there are retrograde (negative) P waves that are clearly seen to occur after the QRS in lead II (red arrows).
      • The rhythm is AIVR (Accelerated IdioVentricular Rhythm) — which is a slower form of ventricular tachycardia.
      Discussion: AIVR is an "enhanced" ventricular ectopic rhythm that occurs faster than the intrinsic ventricular escape rate (which is ~20-40/minute— and slower than hemodynamically significant Ventricular Tachycardia (ie, VT at rates >130-140/minute).
      • The usual rate of AIVR is therefore between ~60-110/minute (with an area of "overlap" between AIVR and fast VT at ~110-130/minute).
      • AIVR generally occurs in one of the following clinical settingsi) as a rhythm during cardiac arrest; ii) in the monitoring phase of acute MI (especially with inferior MI); or iii) as a reperfusion arrhythmia (following thrombolysis, acute angioplasty, or spontaneous reperfusion). It may also occur in patients with underlying coronary disease, cardiomyopathy, with digoxin toxicity — and rarely in otherwise healthy subjects without underlying heart disease.
      • AIVR is often an "escape rhythm" — in that it arises because both the SA and AV nodes are not functioning. IF treatment is needed (because loss of the atrial "kick" results in hypotension) — Atropine is the drug of choice (in hope of speeding up the SA node to resume its pacemaking function). AIVR should not be shocked nor treated with antiarrhythmic medication such as Amiodarone/Procainamide — since doing so might result in asystole ...
      We do NOT know why the patient in this case presented with runs of AIVR (possibly for a period of years ... ). Recent or remote ischemia/infarction and cardiomyopathy should be ruled out. The possibility of SSS (Sick Sinus Syndrome) — with emergence of AIVR as an escape rhythm should also be considered as part of the work-up. Unfortunately — We have no follow-up ...

      ACKNOWLEDGMENT: My appreciation goes to Sam Walker (from Auckland, New Zealand) for allowing me to use this case and these tracings. 
      - For more information  GO TO:
      • For a review pdf of basic Rhythm Interpretation ( = Section 02.0 from my ECG-2014-ePub) — GO TO — AIVR is reviewed in Section 02.38.
      • For full review of additional more complex tracings obtained on this patient — Please see our ECG Blog #107.