Friday, October 28, 2011

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

1 comment:

  1. sir u r doing agreat job........i m really impressed.......seriously...