The document discusses the conduction system of the heart and bundle branch blocks. It notes that a bundle branch block is diagnosed when the QRS duration is over 120ms, there is a dominant S wave in V1, and a broad R wave in lateral leads. It lists causes of bundle branch blocks as conditions like aortic stenosis, dilated cardiomyopathy, and hypertension. The document explains that in left bundle branch block, conduction delay means the left ventricle is activated later via the septum, producing tall R waves in lateral leads and deep S waves in precordial leads, with an extended QRS duration. It also discusses right bundle branch block and criteria for diagnosing a myocardial infarction in the setting of left bundle branch block

1. Conduction system of
heart
Part1
DR.SRUTHI MEENAXSHI
PDF IN VMCRH

2. Electrical system of heart

3. Bundle Branch Block

4. QRS duration > 120ms
Dominant S wave in V1
Broad monophasic R wave in lateral leads (I, aVL, V5-6)
Absence of Q waves in lateral leads
Prolonged R wave peak time > 60ms in leads V5-6

5. The heart rhythm must be supraventricular in origin
The QRS duration must be ≥ 120 ms[2]
There should be a QS or rS complex in lead V1
There should be a notched ('M'-shaped) R wave in lead V6.

7. QRS duration > 120ms
Dominant S wave in V1
Broad monophasic R wave in lateral leads (I, aVL, V5-6)
Absence of Q waves in lateral leads
Prolonged R wave peak time > 60ms in leads V5-6

8. CAUSES
Aortic stenosis
Dilated cardiomyopathy
Acute myocardial infarction
Extensive coronary artery disease
Primary disease of the cardiac electrical conduction system
Long standing hypertension leading to aortic root dilatation and subsequent aortic regurgitation
Lyme disease
Side effect of some cardiac surgeries (e.g., aortic root reconstruction)

11. In LBBB, conduction delay means that impulses travel first via the right bundle branch to the RV,
and then to the LV via the septum
Septal activation is thus reversed eliminating lateral Q waves
The overall depolarisation vector from the right to left ventricle produces tall R waves in lateral
leads (I, V5-6) and deep S waves in the right precordial leads (V1-3). The delay between activation
of the RV and LV produces the characteristic “M-shaped” R wave seen in lateral leads
Delayed overall conduction time to the LV extends the QRS duration to > 120 ms

12. Chapman sign

16. How to diagnose MI in LBBB

17. Sgarbossa criteria

19. Diagnostic criteria
QRS duration > 120ms
RSR’ pattern in V1-3 (“M-shaped” QRS complex)
Wide, slurred S wave in lateral leads (I, aVL, V5-6)

21. RBBB

26. causes
Right ventricular hypertrophy / cor pulmonale
Pulmonary embolus
Ischaemic heart disease
Rheumatic heart disease
Congenital heart disease (e.g. atrial septal defect)
Myocarditis
Cardiomyopathy
Lenègre-Lev disease: primary degenerative disease (fibrosis) of the conducting system

27. Thankyou