MEDICINE 2013
1. LBBB is seen with all except:
a. Acute MI
b. Ashmann syndrome
c. Hypokalemia
d. Hyperkalemia
Answer: B : Ashman syndrome:
Reference: current diagnosis and management in cardiology, chapter19 :
supraventricular tachycardia
· Normally the septum is activated from left to right, producing small Q waves in
the lateral leads.
· In LBBB, the normal direction of septal depolarisation is reversed (becomes
right to left), as the impulse spreads first to the RV via the right bundle branch
and then to the LV via the septum.
o This sequence of activation extends the QRS duration to > 120 ms and
eliminates the normal septal Q waves in the lateral leads.
o The overall direction of depolarisation (from right to left) produces tall R
waves in the lateral leads (I, V5-6) and deep S waves in the right
precordial leads (V1-3), and usually leads to left axis deviation.
· As the ventricles are activated sequentially (right, then left) rather than
simultaneously, this produces a broad or notched (‘M’-shaped) R wave in the
lateral leads.
Causes of LBBB are:
· Aortic stenosis
· Ischaemic heart disease
· Hypertension
· Dilated cardiomyopathy
· Primary degenerative disease (fibrosis) of the conducting system (Lenegre
disease)
· Hyperkalaemia
· Digoxin toxicity
Ashman phenomenon is seen in atrial fibrillation. U all know atrial
fibrillation has irregularly irregular pulse leading to irregular RR interval in ECG.
MEDICINE 2013
This means there is very fast conduction occurring via bundle of his which is
receiving these impulses from a supraventricular phenomenon. Now the point is
that the two fascicles of bundle of his have different refractory periods. Thus if
an impulse lands on the bundle of his and finds the right bundle refractory then
RBBB will occur. Also remember that the refractory period of right fascicle is
more than that of the left fascicle resulting in RBBB.
supraventricular tachycardia
· Normally the septum is activated from left to right, producing small Q waves in
the lateral leads.
· In LBBB, the normal direction of septal depolarisation is reversed (becomes
right to left), as the impulse spreads first to the RV via the right bundle branch
and then to the LV via the septum.
o This sequence of activation extends the QRS duration to > 120 ms and
eliminates the normal septal Q waves in the lateral leads.
o The overall direction of depolarisation (from right to left) produces tall R
waves in the lateral leads (I, V5-6) and deep S waves in the right
precordial leads (V1-3), and usually leads to left axis deviation.
· As the ventricles are activated sequentially (right, then left) rather than
simultaneously, this produces a broad or notched (‘M’-shaped) R wave in the
lateral leads.
Causes of LBBB are:
· Aortic stenosis
· Ischaemic heart disease
· Hypertension
· Dilated cardiomyopathy
· Primary degenerative disease (fibrosis) of the conducting system (Lenegre
disease)
· Hyperkalaemia
· Digoxin toxicity
Ashman phenomenon is seen in atrial fibrillation. U all know atrial
fibrillation has irregularly irregular pulse leading to irregular RR interval in ECG.
MEDICINE 2013
This means there is very fast conduction occurring via bundle of his which is
receiving these impulses from a supraventricular phenomenon. Now the point is
that the two fascicles of bundle of his have different refractory periods. Thus if
an impulse lands on the bundle of his and finds the right bundle refractory then
RBBB will occur. Also remember that the refractory period of right fascicle is
more than that of the left fascicle resulting in RBBB.
