ECG Blog #145 – (ST Depression – STEMI – BBB)

The ECG in Figure-1 was obtained from a 60-year old woman who presented to the ED (Emergency Department) with new-onset chest pain.

• The initial emergency care provider interpreted this tracing as showing complete RBBB ( = Right Bundle Branch Block). Do you agree? 
• Are you concerned about anything else?

Figure-1: 12-lead ECG from a patient with new-onset chest pain. How do you interpret this tracing?

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Interpretation: In a patient with new-onset chest pain — this tracing should be of obvious concern. The rhythm appears to be sinus tachycardia at a rate of ~120/minute. Complete RBBB is present. But there is much more going on than just RBBB ... 

• Beyond-the-Core NOTE: Although it clearly appears that there are upright P waves with a constant and normal PR interval in lead II — a number of leads also display some sort of ‘notching’ toward the tail end of the QRS complex (especially leads II, III, aVR, V4, V5). Caliper measurement suggests that the timing of these extra deflections is not quite at the precise midpoint between sinus P waves (as I would expect it to be if there was 2:1 AV conduction). Thus, although I am fairly confident that the rhythm here is indeed sinus tachycardia — I am not 100% certain, and would entertain the possibility that there could be 2:1 conduction … The point to emphasize is that sometimes it is simply not possible to be 100% certain of the rhythm at the time you need to initiate management. That said, in this case regardless of whether this rhythm is sinus tachycardia or atrial flutter (or atrial tachycardia) with 2:1 AV conduction — initial clinical priorities are similar.
• The QRS complex is wide. QRS morphology is consistent with complete RBBB (ie, predominantly upright QRS in lead V1 — with wide terminal S waves in leads I and V6). However, a deep Q wave is present in lead V1. This suggests that in addition to RBBB — septal infarction has probably occurred at some point in time.
• There is ST segment elevation in lead V1 (by ≥3mm! ). This should not be seen with simple RBBB (See my ECG Video Pearl #22 on the Basics of BBB in ECG Blog #204). Using the principle of “neighboring leads” — it should be apparent that there is also some coved ST segment elevation in neighboring lead V2! Normally with RBBB — one expects the ST-T wave to be at least slightly depressed in anterior leads in which a RBBB-pattern is seen.
• There is also marked ST elevation (of 3-4mm) in lead aVR. Virtually all other leads on this tracing manifest ST depression, which is marked (up to 5-6mm) in many leads! The finding of diffuse ST segment depression (ie, in at least 6-7 leads) in association with ST elevation in lead aVR strongly suggests diffuse subendocardial ischemia as the cause.

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Clinical Impression: At the least, the rhythm in this 60-year old woman with new chest pain is sinus tachycardia. Serial ECG monitoring should clarify whether extra P waves are or are not present. There is complete RBBB — evidence of prior septal infarction at some point in time — and, of most concern strong suggestion of diffuse subendocardial ischemia.

• Although on occasion, ST segment elevation may also be seen in lead V1 (in addition to aVR) when there is subendocardial ischemia — ST elevation is usually not seen in lead V2. Especially in view of the deep Q wave in lead V1 — one should consider the possibility of acute septal infarction.
• Otherwise, when the ECG picture of diffuse ST depression in association with ST elevation in leads aVR and V1 is seen — this is most often not due to acute coronary occlusion. Instead, severe coronary disease (ie, left-main, proximal LAD and/or multi-vessel disease) is most often found. Given the severity of this patient’s new-onset chest pain — the marked tachycardia — the RBBB conduction defect — and, the dramatic amount of ST segment deviation — prompt diagnostic cardiac catheterization is clearly indicated for this patient. This hopefully will suggest potential for life-saving PCI (percutaneous coronary intervention).

Follow-up: Cardiac catheterization confirmed the presence of very severe 3-vessel disease.

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Acknowledgment: My thanks to MG for allowing me to use this tracing and clinical case.
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Additional Material: For Review on ECG Diagnosis of the Bundle Branch Blocks — See my 13-minute ECG Video Pearl #22 on this subject (GO To ECG Blog #204).