ECG Interpretation Review #31 (A Fib – RBBB – LBBB – IVCD – LAD – Infarct with BBB/Conduction Defects)

The ECG shown below was obtained from a 63 year old man with chest pain.  How would you interpret his tracing and accompanying lead II rhythm strip?  What is there to worry about?

Figure 1 – 12-lead ECG and lead II rhythm strip from a man with chest pain. 

INTERPRETATION:  There is a lot to be concerned with on this tracing.  The rhythm is irregularly irregular at an average rate of more than 100/minute.  Although there are fine undulations in the baseline, no definite P waves are seen in the lead II rhythm strip at the bottom of the tracing.  Thus, the rhythm is atrial fibrillation with a fairly rapid ventricular response.

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REGARDING QRS MORPHOLOGY:

The QRS complex is clearly wide.  QRS morphology in leads V1 and V6 is consistent with a bifascicular block pattern of RBBB (Right Bundle Branch Block) with LAHB (Left Anterior HemiBlock).  However, the monophasic R wave in lead I is not consistent with RBBB, but rather with a LBBB (Left Bundle Branch Block) pattern.  Description of QRS morphology in this tracing might therefore better be classified as IVCD with LAD (IntraVentricular Conduction Delay with Left Axis Deviation). 

• NOTE: The basics of assessing ECGs for the presence of RBBB, LBBB, and IVCD were covered in ECG Blogs #3, #11 and #13. We review this entire subject in our ECG Video on the Basics of BBB.

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PUTTING IT TOGETHER:
In view of this patient’s presentation (ie, chest pain) – the most important finding on this tracing is the subtle appearance of Q waves with slight but definite ST segment coving and elevation in leads V1 and V2.  T wave inversion in these two leads is an expected accompaniment of RBBB – but the ST segment elevation is not.  At times, a QR rather than RSR’ complex may be seen in lead V1 with RBBB – but a Q wave will usually not be seen in both leads V1 and V2 with RBBB unless there has been infarction.

• Detection of acute myocardial infarction is always more challenging in the presence of a conduction defect.  This is especially true with LBBB, since infarction Q waves are rarely written, and ST-T wave changes will often be masked by the underlying LBBB.  Recognition of acute ischemia or infarction is still challenging in the presence of RBBB, but the findings seen in leads V1 and V2 of this tracing in the setting of new-onset chest pain should suggest the possibility that acute infarction may be occurring.  

Clinical correlation and comparison with a prior tracing on this patient would help clarify if the findings in leads V1 and V2 are new or old.

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– See also ECG Blog Reviews #3, #11, #13 – and our ECG Video on Basics of BBB –

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ADDENDUM (3/24/2018): In response to the Question by MG (See below), I am writing this Addendum. On review today of this post (that I wrote nearly 7 yerars ago, back in 2011 … ) — I would add the possibility of a Brugada pattern in leads V1,V2 accounting for the ST-T wave appearance in these leads. Problems in knowing for certain what is happening are: i) The very atypical QRS morphology, that is not fully consistent with either RBBB or LBBB; ii) the very small amplitude of the QRST complexes in leads V1,V2; and iii) My lack of clinical follow-up of this case. What I can say, is that the small QR complexes in lead V1,V2 + the wide terminal S in lead V6 are consistent with RBBB and probable anteroseptal infarction at some point in time. Whether the small amplitude ST segment elevation with downsloping into T wave inversion that is present in these leads represents recent infarction — vs a Brugada pattern — (vs some combination of the 2) — I think is impossible to be certain of given the above limitations. Many factors may be associated with an ECG pattern known as “Brugada Phenocopy” (See https://youtu.be/h1MhtLMF-7M?t=9m17s ) — and close clinical follow-up would be needed to determine whether this might be present here. Along the way, I’d still want to rule out the possibility of an acute event in this patient with new chest pain. My THANKS to MG, for his astute question on this case.