Steps for Normal Depolarization The electrical impulse progress through the RBB and LBB and Fascicles simultaneously. Depolarization of IVS Synchronous Depolarization of RV & LV Note: The electrical activity generated by the depolarization of the smaller RV is buried in that generated by the LV.

Depolarization of Septum Depolarization of the Interventricular Septum of the endocardial to epicardial of the ventricular wall is call the Ventricular Activation time (VAT) or the Preintrinsicoid Deflection (IDT), the duration of the Intrinsicoid Deflection or the R peak time.

VAT Measurement Onset of the QRS complex to the peak of the last R wave in the QRS complex. Normally less than.04 second in V1 or V2 or less than.06 second in V5 and V6. RBBB & RVH -the VAT is prolonged in leads V1 & V2 LBBB & LVH-the VAT is prolonged in Leads V5 & V6

Pathophysiology of the BB and Fascicular Blocks Ischemia heart disease Acute Mi Idiopathic degenerative disease of Conduction system Cardiomyopathy LVH Aberrant ventricular conduction Miscellaneous causes such as –Acute or chronic HF, PE, AoValve Disease, Tumors, Trauma, Potassium overdose

Right Bundle Branch Block The electrical impulses are prevented from entering the RV directly because of disruption of conduction system. RBBB present with intact viable IVS RBBB present without intact viable IVS ECG characteristics of the two RBBB’s differ significantly Compare Leads 1 & V1, V6

RBBB Impulses travel down the LBB in to the IS & LV-(Normal) IS to right to enter the RV after a short delay LV depolarize in normal way: first the septum from left to right Then the LV from right to left LV depolarization RV depolarizes in a normal direction Delay results in a wide bizarre shape/appearance.12 seconds or greater (complete).10 and.11 seconds (incomplete)