Makindo Medical Notes

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:

• ECG - Left Bundle Branch Block (LBBB)
• Usually pathological and may warrant further assessment
• The left bundle branch supplies the left ventricle

Aetiology:

• Right ventricle (RV) depolarises first
• Left ventricle (LV) depolarises second
• Total ventricular depolarisation is slower, resulting in a wider QRS complex

Appearance:

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

Note: A new LBBB in the setting of chest pain must be treated as a medical emergency and possible STEMI.

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

Prolonged QRS, absent q wave in V5 and V6, with prominent ST segment and T wave changes

Causes of LBBB:

• Acute STEMI / NSTEMI / Ischaemic heart disease
• Left ventricular hypertrophy (LVH), Aortic valve disease
• Myocarditis, Cardiomyopathy, Right ventricular pacemaker

Clinical Features:

• The aortic valve closes after the pulmonary valve, reversing normal physiology
• Delayed LV activation and contraction with a split second heart sound on expiration

Management:

• Usually pathological and may require further assessment
• In the context of chest pain, a new LBBB may represent a STEMI equivalent