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Left Bundle Branch Block Left Bundle Branch Block (Example 1) Left Bundle Branch Block (Example 2) Left Bundle Branch Block (Example 3) Left Bundle Branch Block (Example 4) Left Bundle Branch Block (Example 5) Left Bundle Branch Block (Example 6) Left Bundle Branch Block (Example 7) Incomplete Left Bundle Branch Block (Example 1) The ECG criteria for a left bundle branch block (LBBB) include: 1) QRS duration of > 120 milliseconds. 2) Absense of Q wave in leads I, V5, and V6. 3) Monomorphic R wave in I, V5, and V6. 4) ST and T wave displacement opposite to the major deflection of the QRS complex. Note: If the QRS duration is between 100-119 milliseconds with criteria 2, 3, and 4 of the above, an incomplete left bundle branch block is present. Traditionally it has been taught that myocardial infarction is not able to be diagnosed via ECG in the presence of a left bundle branch block (LBBB), however Sgarbossa et al in 1996 described some ECG changes seen in those with LBBB and concominant myocardial infarctions and devised a point scoring system. 1) ST elevation > 1 mm and in the same direction (concordant) with the QRS complex. 5 points 2) ST depression > 1 mm in leads V1, V2, or V3. 3 points 3) ST elevation > 5 mm and in the opposite direction (discordant) with the QRS. 2 points A score of 3 points is required to diagnose an acute myocardial infarction. Criteria #3 is under debate as to its usefullness, so basically you need to have either criteria 1 or criteria 2. Our patient just made 1 mm ST elevation in lead V5 and about 0.5 mm ST elevation in V6. This ECG was indeed from a patient with an acute left anterior descending thrombosis.  |
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