Look familiar? This is the yesterday’s ECG taken from Sgarbossa et al.  1996.  Is this a true LBBB?

AHA/ACCF/HRS consensus definition of Complete LBBB:

1)      QRS duration greater than or equal to 120 ms in adults, greater than 100 ms in children 4 to 16 years of age, and greater than 90 ms in children less than 4 years of age.

2)      Broad notched or slurred R wave in leads I, aVL, V5, and V6 and an occasional RS pattern in V5 and V6 attributed to displaced transition of QRS complex.

3)      Absent q waves in leads I, V5, and V6, but in the lead aVL, a narrow q wave may be present in the absence of myocardial pathology.

4)      R peak time greater than 60 ms in leads V5 and V6 but normal in leads V1, V2, and V3, when small initial r waves can be discerned in the above leads.

5)      ST and T waves usually opposite in direction to QRS.

6)      Positive T wave in leads with upright QRS may be normal (positive concordance).

7)      Depressed ST segment and/or negative T wave in leads with negative QRS (negative concordance) are abnormal.

8)       The appearance of LBBB may change the mean QRS axis in the frontal plane to the right, to the left, or to a superior, in some cases in a rate-dependent manner.


Sgarbossa EB, Pinski SL, Barbagelata A, et al, for the GUSTO-1 investigators. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle branch block. N Engl J Med 1996;334:481–7.

Surawicz B, Childers R, Deal BJ, et al. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society. Endorsed by the International Society for Computerized Electrocardiology. J Am Coll Cardiol. 2009;53(11):976.