Diagnostic criteria

  The QRS width should be greater than or equal to

                  120 ms in adults,

                  100 ms in children of 4-16 years,

                  90 ms in children under 4 years of age.

  Wide, notched R wave in leads I, aVL, V5 and V6.

      Occasionally, RS pattern may be seen in leads V5 and V6.

  q waves are absent in leads I, V5 and V6. A small q wave may be present in lead aVL.

  ST and T wave are generally opposite in direction to QRS.

  Positive T waves in leads with positive QRS may be normal (
positive concordance).

  Depressed ST segment and/or negative T wave in leads with negative QRS

      (
negative concordance) are abnormal.

  The development of LBBB may change the mean QRS axis to the right or to the left.

      This change may be in a rate dependent manner.

  R peak time is >60ms in leads V5 and V6. If there are small r waves in leads V1, V2 or V3,

      the R peak time may be normal in these leads.




LBBB pattern - Incomplete LBBB

  QRS duration is between

                  110-119 ms in adults,

                  90-100 ms in children between 4-16 years old,

                  80-90 ms in children between 0-4 years of age.

  There is left ventricular hypertrophy pattern.

  q waves are absent in leads I, V5, and V6.

  R peak time is >60 ms in leads V4, V5, and V6.




LBBB and acute myocardial infarction

Diagnosis of acute myocardial infarction in patients wih LBBB is generally not easy.
In patients with clinical findings suggestive of acute myocardial infarction,
observation of the following ECG findings
may help in diagnosing the acute myocardial infarction.

 
Concordant (with the QRS complex) ST segment elevation of at least 1mm (most important criteria).

  1 mm or more ST segment depression in leads C1, C2 or C3.

  At least 5mm or more ST segment elevation which is discordant with the QRS complex.

 
Cabrera's sign: Notching 0.04 second in duration in the ascending limb of the S wave of

      leads C3 or C4.

 
Chapman's sign: Notching of the upstroke of the R wave in leads I, aVL, or V6.

      (Chapman's sign may also be seen in some patients with Dilated CardioMyoPathy).

  The presence of rS configuration in lead C6.

  Positive T waves in leads with positive QRS complex.




Below, the ECGs 4a and 4b clearly demonstrate how LBBB can mask the signs of ischemia
during myocardial infarction.




Reference

  Circulation 2009;119:e235-e240 .

  Cardiol Clin 1987;5:393-401.





ECG 1. Left bundle branch block.
RR' in I and C6 , deep and wide S wave in C1 is seen.

Click here for a more detailed ECG





ECG 2. Left bundle branch block in another patient. This subject also has mitral stenosis.
The notched P wave in lead II suggests left atrial abnormality.


Click here for a more detailed ECG





ECG 3. Left bundle branch block pattern in a patient with systemic hypertension. The 4th and 5th beats from the left side
make the ventricular couplet.


Click here for a more detailed ECG





ECG 4a. The above ECG is from an 80 years-old woman with chest pain and acute non-ST elevation myocardial infarction.
It shows signs of myocardial ischemia:
negative T waves and ST segment depression in anterior leads.
The heart rate is about 81/minute


Click here for a more detailed ECG



ECG 4b. When the heart rate increased slightly up to 88/minute, rate-dependent left bundle branch block appeared and
masked the electrocardiographic signs of myocardial ischemia.


Click here for a more detailed ECG



Figure 1. Her coronary angiography showed significant stenoses in the

LAD
( Left Anterior Descending ) and Cx ( CircumfleX ) coronary arteries.





ECG 5a. The ECG above belongs to a 25 years-old puerpera (one day after childbirth). Atrial bigeminy is seen.

Every P wave originating from the sinus node
is followed by a premature
P wave originating from an ectopic focus
in the atria.
The premature P wave is negative in the above ECG, suggesting a low atrial focus.
However, all atrial premature beats should NOT necessarily be negative.
Negativity of the P wave is related to its focus, but not to its prematurity.


Click here for a more detailed ECG



ECG 5b. A few hours later, her ECG shows that atrial premature contractions are now coming earlier and being conducted with
aberration.
Some P waves are conducted normally to the ventricles . Some premature P waves are conducted with left
anterior fascicular block (LAFB)
while some others are conducted with left bundle branch block (LBBB) morphology.

Click here for a more detailed ECG





ECG 6. Coexistence of left bundle branch block and atrial fibrillation.

Click here for a more detailed ECG





ECG 7. Cabrera's sign and LBBB. The rhythm is atrial fibrillation.

Click here for a more detailed ECG





ECG 8. The ECG above was recorded immediately after implantation of a stent to the LAD coronary artery for acute anterior
myocardial infarction.
LBBB is accompanied by the
Cabrera's sign.
Baseline drift artifact is also seen.

Click here for a more detailed ECG





ECG 9. The ECG above is from a middle-aged man experiencing acute myocardial infarction.
It was recorded just before stenting of the Circumflex (Cx) coronary artery.
LBBB is accompanied by the
Cabrera's sign.

Click here for a more detailed ECG





ECG 10. By definition, some patients with LBBB may have an
RS pattern in lead V6. RR' pattern in lead V6 is not a necessity.
The compact ECG above is from a 73 years-old man with a history of old anterior myocardial infarction and coronary artery
bypass graft surgery. He has severe left ventricular systolic dysfunction (with an Ejection Fraction of 23%).




Page 1 - Page 2