What is lurking underneath this new right bundle branch block?

Written by Pendell Meyers, edits by Smith:

Case

A 72 year old female with hypertension and COPD presented with sudden shortness of breath and chest pain.

Here is her triage ECG (the baseline is not available but reportedly "normal"):

What is your interpretation?

There is sinus rhythm with PACs and PVCs.

More important, there is right bundle branch block with hyperacute concordant T-waves in V3-V6, as well as hyperacute T-waves in leads III and aVF with reciprocal ST depression in aVL. This distribution is classic for a type III "wraparound" LAD occlusion.

As a general rule, right bundle branch block should usually not have any ST elevation anywhere on the ECG, and the leads with large R' waves such as leads V1 and V2 should have either baseline J-points or some slight ST depression, with negative T-waves.

The rhythm is interesting but not particularly relevant. After the PVC, there is return of sinus rhythm for one beat, then a PAC, then three sinus beats, then a pause followed by a low atrial escape beat, etc. See Ken Grauer's excellent discussion on the rhythm in the comments below.

For comparison, here is an example of RBBB without any superimposed ischemic changes:

Notice normal ST depression in V1-V3 that is discordant (in the opposite direction of) the majority of the QRS, which is the last part of the QRS (R'-wave)

Initial troponin was negative. She was not taken immediately for cardiac cath, as these findings were not appreciated in the setting of RBBB. She was admitted to the cardiology unit. The second troponin I returned elevated at 6.4, and for some reason there were no more troponins measured after that.

Repeat ECG the next morning:

Resolution of findings above, as well as new deep T-wave inversions in V3-V6 and inferior leads, consistent with reperfusion.

On day 3 of hospitalization she underwent coronary angiography, revealing a 95% lesion in the mid-LAD which was stented.  One can say with full confidence that is was completely occluded at the time of the presentation ECG. Peak troponin, echocardiographic findings, and long term outcome are unknown.





Learning Points:

1. RBBB should usually not have any ST elevation, and will usually have some ST depression and T-wave inversion in the right precordial leads.

2. The combination of findings consistent with acute coronary occlusion in the anterior and inferior leads is likely due to a large "wraparound" LAD occlusion, should not be confused with the "diffuse" ST elevation of pericarditis, and will usually show reciprocal ST depression in aVL.

3. The rules of appropriate concordance apply to all forms of abnormal ventricular conduction.  In the case of RBBB, which has an up-down-up complex in right precordial leads V1-V3, it is the last part of the QRS which determines the expected discordant ST segment (the last part is a positive R'-wave, and therefore discordance will manifest as ST depression in V1-V3.

4. T-waves are just as important or more so than the ST segments when looking for acute coronary occlusion.

5. A new right bundle branch block in a sick patient with chest pain and/or shortness of breath is a worrisome finding concerning for LAD occlusion or significant pulmonary embolism.

Left Bundle Branch Block (LBBB) with Chest Pain, concordant and excessively discordant ST depression V2-V6

A middle-aged male presented pain free after an episode of chest pain.  Here is the initial ECG (sorry some is cut off -- it is an iPhone shot from a friend):


There is LBBB with appropriate discordance of all ST segments.  Anterior ST elevation is appropriate, with highest ST/S ratio of 3.5/28 = 0.125 (mean normal = 0.11; normal up to 0.19).  There are concordant T-waves in V5 and V6.  This is a nonspecific sign of NonSTEMI.

 5 minutes later, the patient had crushing chest pain, and this ECG was recorded (again, some of limb leads are cut off):

Now there is concordant ST depression in V2 and V3.  This is a relative change of approximately 5 mm(!).   There is excessively discordant ST depression in V4-V6.   (V4 ratio is 2/6 = 0.33; V5 ratio = 2.5/6.5 = 0.38;  V6 = 2/6.5 = 0.31).  Thus, there is ischemic ST depression in V2-V6.   In normal conduction, ST depression from V2-V6 is often due to subendocardial ischemia, whereas when limited to V1-V4, it is usually posterior STEMI.  Either way, this is a patient with acute coronary syndrome with chest pain.  If you cannot control the symptoms with medical therapy, then the patient must go to the cath lab.   

I have written about excessively discordant ST elevation, but have not mentioned excessively discordant ST depression.  In our study of LBBB with and without coronary occlusion, just one lead with excessively discordant ST depression or ST elevation, as defined as a ratio of ST depression (or elevation) to the preceding R-wave (or S-wave), greater than 0.25, was very specific for ischemia (in our study, for occlusion).  More recent analysis of the data showed that 0.20 was probably a better cutoff.

The physician called the interventionalist, who did not agree there was ischemia on the ECG.  The patient was started on nitroglycerine IV and the pain subsided, as did the ECG findings. 

The patient was admitted pain free on nitro and no immediate cath was done.  The troponin I peaked later at 0.18 ng/ml. 

The next AM, the patient had another episode of pain that could not be resolved with maximal medical therapy.  He went for emergent cath, which showed a proximal lad 95% stenosis with deep ulcer and a 90% mid lad stenosis.  Both were stented.

Later, the troponin peaked at 5.6, and echo showed anteroseptal hypokinesis with EF <40%.

So this was LBBB with concordant and excessively discordant ST depression, representing ST depression in leads V2-V6, completely consistent with subendocardial ischemia due to profound LAD ischemia.

LBBB with acute STEMI due to ruptured obtuse marginal, diagnosed with bedside ultrasound

This 74 yo male had just returned to his unit bed after successful PTCA of tight lesions of the first diagonal and obtuse marginal coronaries. He complained of chest pain. This ECG was recorded. The previous is below.

There is LBBB with concordant ST elevation in II and aVF (inferior STEMI) and V6 (lateral STEMI); also concordant ST depression in V2 and V3 (Posterior STEMI). There is also excessively discordant ST elevation in V5 (ST/S ratio 2:5 = 40%; excessive is > 20%). Compare with baseline ECG below.

Here, all ST segment are appropriately discordant; none excessively so. Maximum discordant ST elevation is in lead V2, (at 4 mm; but this is only 7% of a 60 mm S-wave)

Suddenly, the patient became hypotensive. The physician (one of our fine EM residents) caring for the patient did an immediate bedside ultrasound. This showed a loculated hyperechoic pericardial fluid (blood with clot).

Patient returned immediately to cath and this confirmed a ruptured coronary artery with pericardial bleeding. A balloon pump was placed and the patient went for immediate CABG.

The circumflex was dissected and will be bypassed any moment now.