You are assigned to do “ECG Review” for the day — which means that you need to review all of the ECGs obtained in your busy Emergency Care Center — to ensure that nothing was overlooked.
The only information you are told about the patient whose ECG is shown in Figure-1 — is that it came from an 83-year-old woman.
- HOW would you interpret this 12-lead ECG?
- Is this a case for which you need to pull the patient’s chart?
- HOW LIKELY is it that a recent cardiac event may have occurred?
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| Figure-1: ECG obtained from an 83-year-old woman. No history provided (See text). |
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NOTE #1: Some readers may prefer at this point to listen to the 11:30 minute ECG Audio PEARL before reading My Thoughts regarding the ECG in Figure-1. Feel free at any time to review to My Thoughts on this tracing (that appear below ECG MP-38).
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- I summarize the information in this Audio Pearl in Figures-2, -3 and -4 in the Addendum below. CLICK HERE — to download a 6-page pdf of this information.
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NOTE: For those who want a user-friendly video review illustrating how to diagnose the Bundle Branch Blocks in less than 5 seconds — I am repeating from ECG Blog #204, my ECG Media Pearl #22 (13:15 minutes Video).
- CLICK HERE — to download a 12-page pdf (from my ECG-2014-ePub) that summarizes the ECG diagnosis of BBB.
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MY Approach to this Tracing:
As always — I favor a Systematic Approach for every ECG I encounter (This Systematic Approach reviewed in ECG Blog #205). My descriptive analysis of the ECG shown in Figure-1 is as follows:
- Rate & Rhythm: The rhythm is fairly (but not completely) regular at a rate just under 50/minute. Although small in amplitude, upright P waves are seen in lead II, with a constant PR interval — therefore the rhythm is sinus bradycardia.
Regarding Intervals:
- The PR interval appears to be upper normal (ie, not clearly more than 1 large box in duration — therefore not clearly >0.20 second).
- The QRS complex is wide. Interval duration should be assessed in whichever lead the onset and offset of the interval can be clearly seen — and in which the interval appears to be longest. QRS duration extends over 3 little boxes ( = 0.12 second) in lead V1, which is wide.
- PEARL #1: Regardless of whatever system you favor for interpretation of 12-lead tracings — it’s important to assess intervals at an early point in the process. This is because IF the QRS complex is wide — then criteria for assessing the QTc, Axis, Chamber Enlargement and Ischemia/Infarction will all change! Therefore, as soon as you recognize QRS widening — STOP — and Figure Out WHY the QRS is Wide before going further in your assessment!
WHY is the QRS Complex Wide?
As discussed in my ECG Media Pearl #22 (above) — once you confirm that the rhythm is supraventricular — the reason for QRS widening can be most time-efficiently determined by focusing attention on the 3 KEYleads (ie, leads I, V1 and V6).
- Lead V1: Normally — lead V1 is predominantly negative. This is because predominant electrical activity is normally directed away from this right-sided lead, and toward the larger left ventricle. Therefore — the finding of a predominantly positive QRS complex, in the form of the QR complex seen in lead V1 of Figure-1 — is not a “normal” finding. And when this predominantly upright QRS complex in lead V1 is wide and assoicated with wide terminal S waves in lateral leads I and V6 — then criteria for RBBB (Right Bundle Branch Block) have been satisfied. This is the case in Figure-1. Although S waves in both leads I and V6 are not overly deep — these terminal S waves are wide (ie, at least 1 little box, therefore ≥0.04 second in duration) — and, therefore confirming the diagnosis of RBBB.
- PEARL #2: When RBBB is “typical” — the QRS complex in lead V1 will manifest an rsR’ pattern in which the initial r wave is small and thin — the S wave that follows this initial small r wave descends below the baseline — and, the terminal R’ is tall and thin (producing a taller right “rabbit ear”). Loss of the initial positive r-wave deflection in lead V1, so as to result in the QR pattern seen in Figure-1 (with a wide and deep Q wave, that is followed by a tall R wave) strongly suggests that septal infarction has taken place at some point in time.
Returning to our Systematic Approach:
Now that we’ve determined the reason for QRS widening (which is complete RBBB) — We can return to our Systematic Approach for assessment of the remaining parameters:.
- QTc: The remaining interval to assess is the QTc. Bundle branch block per se may prolong the QTc. That said — the longest QT that I measure in Figure-1 looks to be ~480 msec, which considering the bradycardia and conduction defect is probably not prolonged. (Visually — the QT interval is decidedly less than half the R-R interval — although the value of this measurement is decidedly less when the ventricular rate is so slow).
AXIS — The “meaning” of axis is altered in RBBB. This is because of the zig-zag direction of electrical activity due to this conduction defect. That is — the initial left-to-right vector of septal depolarization is preserved (since the conduction defect with RBBB is on the right side of the septum) — which is followed by depolarization of the unblocked LV (during which time the wave of depolarization travels back to the left) — and finally, return rightward, as the “blocked” RV is the last part of the heart to depolarize.
- Clinically — the only thing we care about regarding the axis with RBBB is whether there is: i) RBBB +LAHB; ii) RBBB + LPHB; or, iii) RBBB without any hemiblock. In Figure-1, neither LAHB nor LPHB are present (LAHB is not present since the QRS in lead II is not predominantly negative — and — LPHB is not present since there is no deep S wave in lead I). Therefore — there is RBBB without any hemiblock.
Chamber Enlargement: There is no RAA, LAA or RVH. There is LVH.
- Criteria for atrial abnormality are unaffected by bundle branch block. However, because RBBB and LBBB alter the sequence of both ventricular depolarization and ventricular repolarization — voltage criteria and ST-T wave changes of LV or RV “strain” will be more difficult to identify.
- That said — because the LV depolarizes unopposed with RBBB (since depolarization of the much smaller right ventricle is delayed by this conduction defect) — the effect of RBBB on ECG diagnosis of LVH may not be marked. How much of an effect RBBB may have on ECG diagnosis of LVH may be difficult to predict. So, realizing that data and definitive answers are lacking — the significantly increased voltage that we see in Figure-1 for the R wave in lead aVL (ie, ~15 mm), in association with the nonspecific ST-T wave flattening that we see in this lead (a "strain" equivalent?) suggests at least probable LVH.
Regarding Q-R-S-T Changes:
- Q Waves — are seen in leads I and V1. The Q wave in lead aVL is both deeper and wider than expected for a normal septal q wave — so it could reflect prior lateral infarction. As noted previously — the very large Q wave in lead V1 suggests prior septal infarction.
- R Wave Progression — is less relevant in this tracing, since RBBB by definition results in a predominant R wave in lead V1.
PEARL #3: There are primary ST-T Wave Changes in multiple leads. As discussed in my ECG Media Pearl #22 (above) and also in ECG Blog #204 — the normal response of ST-T waves in the 3 KEY leads with BBB is to be oppositely directed to the last QRS deflection.
Looking first at the 3 KEY leads — the ST-T waves in leads I, V1 and V6 are all clearly abnormal.
- In both of the lateral leads ( = leads I and V6) — the ST segment is abnormally coved, and the T wave is symmetrically inverted (instead of showing a normal upward-sloping ST segment with upright T wave — as illustrated below in Figure-2 of the Addendum).
- In lead V1 — the ST segment appears to be slightly elevated, and the T wave is clearly upright (whereas the expected response with RBBB is for there to be some ST-T wave depression in lead V1 — as shown in Figure-2).
Looking next at neighboring leads:
- Lead V2 shows a similar upright T wave as is seen in lead V1. Normally, with simple RBBB — there should be ST-T wave depression in at least several anterior leads.
- The remaining chest leads ( = leads V3, V4, V5 and V6) all show abnormal ST segment coving and fairly deep, symmetric T wave inversion that is clearly abnormal.
- Similar ST segment coving and fairly deep, symmetric T wave inversion is seen in each of the inferior leads ( = leads II, III, aVF).
Putting It All Together:
The ECG in Figure-1 shows the following abnormalities:
- Fairly marked sinus bradycardia.
- RBBB
- Probable LVH
- A deeper-than-expected Q wave in lead aVL of uncertain significance (possibly indicative of prior lateral infarction).
- A QR pattern in lead V1 — with a deep and very wide initial Q wave in this patient with RBBB (strongly suggesting prior septal infarction at some point in time).
- Clearly abnormal ST-T wave abnormalities in no less than 10 of 12 leads — which in this 83-year-old woman strongly suggests ischemia if not recent infarction (possibly very recent).
- BOTTOM LINE: The only way to determine if the above abnormalities are new — recent — or old — is to pull this patient's chart and possibly contact this patient (depending on what information and additional ECGs are found in the chart).
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Related ECG Blog Posts to Today’s Case:
- ECG Blog #205 — Reviews my Systematic Approach to 12-lead ECG Interpretation (outlined in Figures-2 and -3, and the subject of Audio Pearl MP-23 in Blog #205).
- ECG Blog #204 — Reviews the ECG diagnosis of the Bundle Branch Blocks (RBBB/LBBB/IVCD).
- ECG Blog #203 — Reviews ECG diagnosis of Axis and the Hemiblocks. For review of QRS morphology with the Bifascicular Blocks (RBBB/LAHB; RBBB/LPHB) — See the video ECG Media Pearl #21 in this blog post.
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ADDENDUM (5/5/2021):
I've reproduced in Figures-2, -3 and -4 below the 6-page section from my ECG-2014-ePub on ECG Diagnosis of Acute MI when there is Bundle Branch Block.
- CLICK HERE to download a 6-page pdf of the information in these Figures.
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| Figure-2: Pages 1,2: The ST Opposition Rule — You can see Q waves with RBBB! |
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| Figure-3: Pages 3,4: Diagnosis of MI with LBBB (Smith-Sgarbossa) — Case Examples. |
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Figure-4: Pages 5,6: Several Case Examples (Cont.). |
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