Thursday, May 16, 2024

ECG Blog #430 — Just a Regular LBBB ECG?

The ECG in Figure-1 — was obtained from an older man who had just completed dialysis — and, is now complaining of abdominal discomfort that radiates to his chest.
  • The consultant interpreted this tracing as “LBBB” (Left Bundle Branch Block) — but not indicative of anything acute.

  • Do you agree with the consultant’s interpretation?
  • How would YOU approach this case?

Figure-1: The initial ECG in today's case. (To improve visualization — I've digitized the original ECG using PMcardio)

MY Initial Thoughts on Today’s CASE:
Given the older age of the patient in today’s case — and, the fact that he just completed dialysis — the chance of having underlying coronary disease is clearly increased. This patient's new complaint of pain that radiates to his chest therefore immediately places him in a higher-prevalence” group for having an acute event (especially since hemodialysis is a procedure in which transient hypotension is not uncommon).
  • For clarity in Figure-2 — I’ve labeled today’s initial ECG. The rhythm is sinus at ~85/minute (the RED arrow highlighing the upright P wave in lead II). The QRS complex is wide — with a morphology most consistent with LBBB ( = predominantly upright in left-sided leads I and aVL — and predominantly negative in the anterior leads).
  • Serum K+ was normal. 

  • NOTE: By my observation over the years — the experts do not agree on the classification of LBBB vs IVCD (IntraVentricular Conduction Defect). As I review in ECG Blog #204 “typical” LBBB is characterized by a supraventricular rhythm with QRS widening, in which there is a monophasic R wave in left-sided leads I and V6 — and an all-negative (or almost all negative) QRS in right-sided lead V1
  • The above said — many patients with LBBB also have marked LVH. Given the leftward and posterior orientation of a markedly enlarged LV (Left Ventricle) — the presence of an all-upright R wave may not be seen in left-sided lead V6. Instead, the all-positive R wave with LBBB may sometimes only appear in more lateral and posteriorly-oriented chest leads, such as V7,V8 or V9.
  • As a result — I would accept either LBBB or IVCD as a “correct” classification of the widened QRS morphology seen in Figure-2. Personally, I favor LBBB in view of the suggestive appearance of LBBB in the limb leads, with fairly deep anterior S waves — but my comments below are consistent with either LBBB or IVCD.

PEARL #1: Regardless of whether you interpreted the widened QRS morphology in today’s ECG as “LBBB” or “IVCD” — there are a number of ECG findings of increased concern beyond that of the conduction defect. Among them: 
  • There should never normally be a Q wave in a lateral lead with simple LBBB. As discussed in ECG Blog #204 — this is because by definition, the conduction defect with LBBB prevents normal left-to-right septal depolarization. The same is true for an IVCD pattern that mimics LBBB in the limb leads (as is seen in today’s ECG). Therefore — the Q waves in Figure-2 (BLUE arrows in leads I and aVL) suggest that in addition to the conduction defect — there is also scar” (usually from infarction at some point in time).

In addition to the abnormal Q waves — ST-T wave morphology is distinctly abnormal in almost every lead!
  • While more difficult to assess because of the lack of an all-upright R wave in lateral lead V6 — the shape of the ST-T waves in multiple leads is just not normal.
  • BLUE lines in leads V2,V3 show abnormal ST segment straightening (instead of the expected upsloping ST segment in these leads).
  • PURPLE lines in leads V4,V5,V6 show abnormal downsloping ST segments (with marked abnormal ST depression in leads V5,V6). In addition — the biphasic T wave with marked terminal positivity in leads V5,V6 looks distinctly acute (ie, T waves are not normally upright in lateral chest leads with LBBB).
  • Similar downsloping with marked, abnormal ST depression and abnormal biphasic T wave with marked terminal positivity — is seen in lead II.
  • While ST segments in leads III and aVF are not nearly as depressed or downsloping (as they are in lead II) — the ST segment straightening that we see in leads III and aVF, with marked angulation at the point where the ST segment meet the beginning of the T wave — is clearly not normal.
  • Finally — note how marked the ST elevation is in lead aVR (within the RED box in this lead).

Putting It All Together:
The older man in today’s case was clearly in a higher-prevalence group for an acute event — even before we looked at his initial ECG. As a result — there was need to assume that any potentially abnormal ECG findings that might be seen are acute until proven otherwise.
  • In summary, the ECG in Figure-2 shows sinus rhythm with LBBB — and diffusely abnormal ST-T wave depression with ST elevation in lead aVR. At the least — this pattern is consistent with DSI (Diffuse Subendocardial IschemiaSee ECG Blog #271 for more on DSI).
  • More than this — the Q waves in leads I and aVL — and the acute appearance of the downsloping ST depression with terminal T wave positivity — might reflect multi-vessel disease with recent and/or ongoing acute infarction.

  • Finding a prior tracing on this patient would be extremely helpful — as it would tell us what is "new" vs old.
  • Obtaining serial ECGs should prove insightful. Especially when correlated to the presence and relative severity of symptoms — serial tracings will convey if acute injury is ongoing. For example — a reduction in symptoms in association with improvement in ST-T wave changes, would suggest that the "culprit" vessel is spontaneously opening!
  • PEARL #2: In patients with ongoing symptoms — ST-T wave elevation and reciprocal ST depression may evolve over a period of minutes. As a result — Consider a repeat ECG as often as every 10-to-20 minutes in a patient with ongoing CP (Chest Pain)  until a definitive diagnosis can be made.

  • BOTTOM Line: On seeing today's ECG — prompt cath was clearly indicated.

Figure-2: I've labeled the initial ECG in today's case. 


Acknowledgment: My appreciation to Mayan Kain (from Tel Aviv, Israel) for the case and this tracing.




Related ECG Blog Posts to Today’s Case:

  • ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation.

  • ECG Blog #193 — Reviews the basics for predicting the "culprit" artery (as well as reviewing why the term "STEMI" — should be replaced by "OMI" = Occlusion-based MI).
  • CLICK HERE  for my new ECG Videos (on Rhythm interpretation — 12-lead interpretation with Case Studies for ECG diagnosis of acute OMI).
  • CLICK HERE  for my new ECG Podcasts (on ECG & Rhythm interpretation Errors — and — Errors in assessing for acute OMI).
    • Recognizing hyperacute T waves — patterns of leads — an OMI (though not a STEMI) — See My Comment at the bottom of the page in the November 8, 2020 post on Dr. Smith's ECG Blog.
    • Recognizing ECG signs of Precordial Swirl (from acute OMI of LAD Septal Perforators— See My Comment at the bottom of the page in the March 22, 2024 post on Dr. Smith's ECG Blog. 

    • ECG Blog #294 — Reviews how to tell IF the "culprit" artery has reperfused.
    • ECG Blog #230 — Reviews how to compare serial ECGs
    • ECG Blog #115 — Shows how dramatic ST-T changes can occur in as short as an 8-minute period.
    • ECG Blog #268 — Shows an example of reperfusion T waves.
    • ECG Blog #400 — Reviews the concept of "dynamic" ST-T wave changes.

    • ECG Blog #337 — A "NSTEMI" that was really an ongoing OMI of uncertain duration (presenting with inferior lead reperfusion T waves).

    • ECG Blog #282 and ECG Blog #204 — review a user-friendly approach to the ECG diagnosis of the Bundle Branch Blocks (RBBB, LBBB and IVCD).

    • ECG Blog #203 — reviews ECG diagnosis of Axis, Hemiblocks and Bifascicular Blocks.


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