Left Bundle Branch Block

This is a great ECG for teaching your students about some of the different causes of wide QRS.  This 89 year old man has a sinus rhythm that is around 100 bpm, and his QRS is widened at 148 ms (.148 sec).  Leads I and V6 are positive, and Lead V1 is negative, meeting the criteria for left bundle branch block. There is a left axis deviation, which is common with LBBB, although it is not always this pronounced, indicating that there is possibly another cause for LAD.  In this ECG, there are also PVCs and probable fusion beats.  The 14th beat is a PVC.  Complexes 1, 6, and 9 are possibly fusion beats. Fusion can be described as an almost simultaneous sinus beat and ventricular beat.  The depolarization waves, one coming from the top of the heart and one coming from the bottom, meet and "fuse" on the ECG.  Fusion beats will have some characteristics of the supraventricular beats and some of the ventricular beats.  They are not significant except that fusion can be said to "prove" the existence of a ventricular pacemaker - either a natural pacemaker or an electronic one.

Do you see anything else interesting in this ECG?  How would YOU describe this rhythm?

This ECG was presented earlier this week as an example of SVT with LBBB aberrancy, which was ultimately converted with one dose of adenosine in the Emergency Department.  It is the most shared and commented on ECG yet to appear on the Guru.  The diagnosis given was the one accepted by the medical staff who cared for the patient, who was a man in his 30's who presented to the Emergency Department complaining of a rapid heart rate.  He was ambulatory with stable vital signs, in spite of the tachycardia. He reported that he has had several episodes of fast heart rate which responded to either Valsalva maneuvers or, in some cases, medication in the ED.  He was told he might benefit from an ablation procedure, but he did not have health insurance and continued to use the ED as his primary source of medical care.  When he was admitted to the ED, the tech initially called for help, thinking the monitor showed ventricular tachycardia.  The ED physician felt that this represented LBBB aberrancy, possibly rate-dependent, and he treated the patient with adenosine.  The rhythm converted to sinus after one dose, and the patient remained stable throughout the process.  He was advised to undergo further observation and testing, but he declined due to financial concerns, and the fact that he usually succeeded in relieving his symptoms with "bearing down".  

Wide-complex tachycardias can be difficult to assess simply from an ECG. The patient's stability depends more upon general health and cardiac output issues than the origin of the tachycardia.  When we presented this ECG, we also presented the diagnosis he had upon discharge from the ED.

Subsequently, ECG Guru Dr. Ken Grauer, a frequent contributer to this site, offered his alternative diagnosis and his explanation of why he believes this to be v tach.  Other well-respected ECG experts have also questioned the original diagnosis.  Please refer to the comments below for this very helpful explanation.  Unfortunately, this patient is lost to followup, as this incident occurred some time ago.

WTCs remain a most fascinating topic, especially for those who enjoy "detective work".  We thank Dr. Grauer, Tom Bouthillet, and others for their contributions to the ECG Guru on this topic.
   

This patient suffered a recent anterior-septal wall M.I., which can be seen as slight ST elevation in V1 and ischemic T wave inversions in V2 through V4. The patient has developed an intermittent left bundle branch block as a result of this M.I.  Every other beat is conducted in a left bundle branch block pattern, as the LBB cannot repolarize in time for each beat.  The criteria for LBBB are:  wide QRS, supraventricular rhythm, and negatively-deflected QRS in V1 with a positive QRS in V6 and Lead I.

This is a good example of wide complex tachycardia that must be evaluated for V Tach vs supraventricular rhythm with left BBB.
The rhythm initially looks regular, but becomes irregular in V1 - V3. No P waves are seen prior to the QRSs, even when the rate slows down. The typical pattern for left bundle branch block exists: wide QRS, negative QRS in V1 and positive QRS in Lead I and V6. The irregularity suggests atrial fibrillation. A longer rhythm strip would be very helpful here. The axis, which is extreme left, could be from V Tach OR left BBB. There is no precordial concordance, favoring LBBB.
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 This wide complex tachycardia has an initial rate of 129/min. It is difficult to discern if P waves are present, although the ECG machine does give us a PR interval. The ECG meets most of the criteria for left bundle branch block: wide QRS, negative QRS in V1, positive QRS in Lead I and V6. However, it is difficult to say for certain that this is a supraventricular rhythm. Later, however, the patient's rate slowed (see top strip), revealing P waves. When the rate slowed, the left bundle branch block pattern remained. That helps confirm the original interpretation of left bundle branch block. Interestingly, the BBB is not rate-related, in that it is still present at the slower rate.
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