ECG - Left Bundle Branch Block LBBB

Related Subjects: |ECG Basics |ECG Axis |ECG Analysis |ECG LAD |ECG RAD |ECG Low voltage |ECG Pathological Q waves |ECG ST/T wave changes |ECG LBBB |ECG RBBB |ECG short PR |ECG Heart Block |ECG Asystole and P wave asystole |ECG QRS complex |ECG ST segment |ECG: QT interval |ECG: LVH |ECG RVH |ECG: Bundle branch blocks |ECG Dominant R wave in V1 |ECG Acute Coronary Syndrome |ECG Crib sheets

About

• Usually Pathological and may warrant further assessment
• Left bundle branch supplies left ventricle

Aetiology

• RV depolarises first
• LV depolarises second
• Total Ventricular depolarisation slower so QRS wider

Appearance

• QRS > 0.12 secs (3 small squares)
• Deep S wave with W pattern V1-3
• RsR' M pattern V6
• Aide memoire WI(LL)IAM

New LBBB in the setting of chest pain must be treated as a medical emergency and possible STEMI

Prolonged QRS duration, q wave absent V5 and V6, no secondary R wave in V1

Prolonged QRS, no q wave in V5 and V6, prominent changes in ST segment and T wave

Causes of LBBB

• Acute STEMI / NSTEMI / Ischaemic heart disease
• LVH, Aortic Valve disease
• Myocarditis, Cardiomyopathy, RV pacemaker

Clinical

• Aortic valve closes after Pulmonary the reverse of normal physiology
• Delayed LV activation and contraction with Split 2nd heart sound on expiration

Management

• Usually Pathological and may warrant further assessment
• In the context of Chest pain new LBBB may represent a STEMI equivalent