ECG Criteria of LBBB

• RSR´- in V5 and V6, also in L1 and aVL (M pattern).
• QRS wide, >0.12 second (3 small squares).

Causes of LBBB

• Severe coronary artery disease.
• Acute myocardial infarction.
• Cardiomyopathy.
• Aortic valve disease (stenosis or regurgitation).
• Left ventricular hypertrophy.
• Hypertension.
• Myocarditis.


• Features of primary disease.


On auscultation, there is reverse splitting of second heart sound.


• Treatment of primary cause.
• In acute myocardial infarction—if there is new LBBB, temporary pacemaker is indicated.