Module 7 - BB Conductions Disorders

The left BB is divided into…

Left anterior fascicle

Left posterior fascicle

List some conditions that can cause a RBBB.

• ASD

• RV hypertrophy

• Ischemic heart disease

• Myocarditis

• HTN

• Cardiomyopathy

• Pulmonary embolism

Why would a patient with a RBBB be prescribed a pacemaker?

Contracting the ventricles simultaneously.

What is this rhythm?

RBBB.

QRS complex is notched and wide.

Why is the QRS complex wide in RBBB?

Impulse travels to LV → RV via myocardial conduction.

Myocardial conduction is slow → wide QRS with a notch from delayed RV depolarization.

What are the two types of RBBB. Describe each. Which is more severe?

Proximal block - delayed TV closure → normal PV opening

• benign and asymptomatic

Distal block - delayed RV contraction → delayed TV closure → delayed PV opening

• likely to cause MI and syncope

List some conditions that can cause a LBBB.

• Aortic stenosis

• DCM

• Acute MI

• CAD

• Post cardiac surgeries

• HTN

• Lyme disease

In a BBB, the QRS complex is >__s

QRS > 0.12s

In a patient with normal SPAP, you notice the IVS bounces into the LV. What condition is this indictive of?

LBBB.

RV pressure increases faster than LV pressure → IVS shifts to the left.

What is this rhythm?

RBBB

Wide, noted QRS in Lead I

Both RBBB and LBBB have wide QRS. How can they be differentiated on ECG?

RBBB - wide S-wave and notched, positive QRS

LBBB - wide QRS in all 12 leads, large R-wave, negative QRS in lead 1, “bunny ears” (not always)

What is this rhythm?

LBBB

Wide QRS throughout

Negative QRS in lead 1

What rhythm is this?

RBBB

RSR pattern in V1

Positive QRS in V1

Not all leads have a wide QRS complex