Bundle Branch Blocks and IVCDs

Question 1

What happens to myocardial cells when deprived of oxygen?

Answer 1

anaerobic metabolism is initiated

Question 2

What does anaerobic metabolism cause

Answer 2

Acidosis and cell death

Question 3

Describe the normal pathway of an impulse

Answer 3

From the SA node to the AV node to the bundle branches, to the myocardium

Question 4

If a bundle is blocked, how will the cells depolarize?

Answer 4

Cell to cell transmission

Question 5

A blocked right bundle causes

Answer 5

A right bundle branch block

Question 6

A blocked left bundle causes

Answer 6

A left bundle branch block

Question 7

What occurs in a right bundle branch block?

Answer 7

An impulse travels to the left ventricle normally but is delayed in the right. This cause RV cell to cell depolarization.

Question 8

What are the three criteria for a right bundle branch block

Answer 8

1. QRS prolongation of ≥0.12 sec
2. Slurred S wave in leads I and V6
3. RSR’pattern in lead V1and V2with R’taller than R

Question 9

Late innervation of septum and RV in RBBB creates…

Answer 9

A new, slower vector

Question 10

The most important criteria for a RBBB

Answer 10

Slurred S waves in I and V6

Question 11

A RBBB may have _____ instead of an RR

Answer 11

A QR wave resembling bunny ears

Question 12

A LBBB always has a QRS of _____ or more

Answer 12

0.12

Question 13

LBBBs will often have

Answer 13

ST elevation/depression

Question 14

T waves in a LBBB will be

Answer 14

Discordant

Question 15

What are the three key criteria for a LBBB

Answer 15

1. Duration ≥0.12 sec wide
2. Broad, monomorphicR waves in I and V6,no Q wave
3. Broad, monomorphicS waves in V1, may have small r wave

Question 16

Common causes of a LBBB include

Answer 16

1. Hypertension
2. Coronary artery disease (CAD)
3. Dilated cardiomyopathy
4. Rheumatic heart disease
5. Infiltrative diseases of the heart
6. Benign or idiopathic causes

Question 17

What cannot be diagnosed with a present LBBB

Answer 17

Ventricular hypertrophy

Question 18

What axis do most LBBBs have

Answer 18

Normal or left

Question 19

Can you diagnose left ventricular hypertrophy with a RBBB?

Answer 19

Yes

Question 20

Are IVCDs localized or spread out?

Answer 20

Either

Question 21

What type of IVCD occurs frequently, has a multi peaked QRS, and often shows in lead 3?

Answer 21

Localized

Question 22

What type of IVCD has wide QRS complexes but lacks all the characteristics of LBBB and RBBB

Answer 22

Non-localized

Question 23

What is a hemiblock

Answer 23

An incomplete LBBB

Question 24

What are the two types of hemiblock

Answer 24

Left anterior and Left posterior

Question 25

Which fascicle is well organized and easy to block?

Answer 25

Left anterior

Question 26

Which fascicle is chaotic and hard to block?

Answer 26

Left posterior

Question 27

How does conduction progress in a LAH

Answer 27

from the interventricular septum, inferior wall, and posterior wall toward anterior and lateral walls

Question 28

List the 3 criteria for a LAH

Answer 28

1. Left axis deviation with axis at –30˚ to –90˚ 2. Either a qRcomplex or an R wave in lead I 3. An rScomplex in lead III, and probably II and aVF

Question 29

What's the shortcut to identify a LAH

Answer 29

Pathological Left axis deviation

Question 30

What are the criteria for a left posterior hemiblock

Answer 30

1. Axis of 90˚ to 180˚ in right quadrant 2. s wave in lead I and q wave in lead III 3. Exclusion of RAE and/or RVH

Question 31

What is a bifascicular block?

Answer 31

A RBB that shares findings with a Hemiblock