Nonischemic regional wall motion abnormality - LBBB Dr sajeer K T Senior Resident, Dept. of Cardiology, Medical College, Calicut

Normal spread of electrical activity in the heart Depolarization of the ventricular muscle starts at the left side of the interventricular septum and moves first to the right across the midportion of the septum

Normally conduction down the left bundle precedes that down the right bundle by 10 to 20 ms Normal initial activation of the heart is in the proximal mid septum on the left ventricular side

LBBB Initial septal activation is reversed. Right side of the ventricular septum is initially activated Right septal activation before activation of the body of the left ventricle Initial right to left movement of the ventricular septum (anterior to posterior)

Interrelation between right and left ventricular events in normal subjects and LBBB

Normal M-mode Echo

Interventricular septal motion in LBBB and the relation to dynamic interventricular asynchrony. Circulation Vol 79, No 4, April 1989

High amplitude oscillations of the IVS LV –RV Asynchrony - Contraction - Ejection - End systole - End diastole Abnormal interventricular septal oscillations

M-mode echocardiogram recorded in a patient with a left bundle branch block shows an early systolic downward motion of the ventricular septum (arrows).

LBBB v/s Ejection fraction Regional ejection fractions of apical and lateral segments similar in normal (NL) and left bundle branch block (LBBB) groups. Septal ejection fraction decreased in LBBB patients (40+16%) compared with normal subjects (67±+7%). Circulation Vol 79, No 4, April 1989

Mechanism for global cardiac abnormalities in isolated left bundle branch block Altered Ventricular Activation Delayed LV Contraction Decreased LV diastolic time LV-RV Asynchrony Abnormal septal Motion Abnormal LV Septal EF

Nonischemic Regional Wall Motion Abnormality

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