Conduction Blocks

Question 2

What is a conduction block?

Answer 2

Any obstruction or delay of the normal pathways of electrical conduction

Question 3

What are the 3 types of conduction blocks?

Answer 3

sinus node block

AV block

bundle branch block

Question 4

What type of block is this:

sinus node fires normally, but wave of depolarization is blocked and not transmitted to atrial tissue

Answer 4

sinus node block

Question 5

What type of block is this:

Any conduction block between the sinus node and Purkinje fibers (including AV node & His bundle)

Answer 5

AV block

Question 6

What type of block is this:

Conduction block in one or both of the ventricular bundle branches

Answer 6

Bundle Branch Block

Question 7

What type of block is this:

only a part of one of the bundle branches is blocked

Answer 7

fascicular block

**a bundle branch block subtype

Question 8

What are the 3 types of AV blocks?

Answer 8

First Degree
 Second Degree (Mobitz I, Mobitz II)
 Third Degree (a complete block)

Question 9

What type of AV block is this:

Rhythm is regular, PR interval > 0.2 seconds, QRS is usually normal

Answer 9

1st degree AV block

Question 10

What AV block is this:

Successively longer PR intervals unil one QRS fails, Rhythm (ventricular) is often irregular, atrial rhythm is ~ regular, QRS is normal, Pwave regular, ventricular wave is not

Answer 10

Second Degree AV Block: Mobitz I (Wenckebach)

Question 11

What type of AV block:

Suddenly dropped QRS, P-waves are punctual and similar, unlike a non-conducted PAC which is EARLY!

Ventricular rhythm = irregular, atrial rhythm is regular

PR interval normal or prolonged, QRS: often abnormal

Answer 11

Second Degree AV block: Mobitz II

(AV block at bundle of His or bundle branches)

Question 12

What type of AV block:

Atria and ventrilces are depolarizing independently

*No association between atria and ventricles

Answer 12

Third degree av block

aka “complete heart block”

Question 13

What type of AV block:

Ultimate in heart blocks.
No atrial impulses make it through to activate the ventricles.
Aka Complete heart block.

Answer 13

Third degree av block

Question 14

What type of AV block:

Ventricles generate an escape rhythm (30-45 BPM).
Atrial and ventricles have nothing to do with each other

Answer 14

Third degree av block

Question 15

What type of block:

Check QRS first

Look in V1 & V2 (overlie Right ventricle) –> R & R’ wave = bunny ears

Look in V5, V6, and Lead I (lateral leads = Left Ventricle) –> Slurred S wave

Answer 15

Right Bundle Branch Block (RBBB)

Question 16

What leads will reflect RBBB?

Answer 16

V1, V2: will have R1R’ wave (bunny ears)

V5, V6, Lead I: will have slurred S wave

Question 17

What type of block:

Answer 17

Left Bundle branch block (LBBB)

Question 18

What leads will reflect LBBB?

Answer 18

V5, V6, or Lead I: “blunted” positive QRS, T-wave inverted

V1-V3: predominately negative QRS

Question 19

What block refers to a conduction block of just one of the fascicles of the left bundle branch.

Answer 19

hemiblock

Question 20

What is the major effect that hemiblocks have on the EKG?

Answer 20

axis deviation

Question 21

What type of block:

Answer 21

left anterior hemiblock

Question 22

What type of block:

• Conduction down the left anterior fascicle is blocked and current rushes down the left posterior fascicle to the inferior surface of the heart. Depolarization goes from inferior to superior and right to left in direction.
• Axis of depolarization is directed upward and slightly left, inscribing tall R waves in the left lateral leads and deep S waves inferiorly.

Answer 22

Left Anterior Hemiblock

(results in left axis deviation)

Question 23

What type of block:

• All of the current rushes down the left anterior fascicle and ventricle myocardial depolarization ensues superior to inferior and left to right in direction.
• The axis of depolarization is down and to the right (RAD), tall R waves in inferior leads and deep S waves in left lateral leads.

Answer 23

Left posterior hemiblock

Question 24

What type of block:

Answer 24

Left posterior hemiblock

Question 25

How do you diagnose hemiblocks?

Answer 25

look for Left axis deviation or Right axis deviation

Question 26

What type of block:

• Normal QRS duration & no ST segment or T wave changes
• LAD
• No other cause of LAD is present

Answer 26

Left anterior hemiblock

Question 27

What type of block:

• Normal QRS duration and no ST segment or T wave changes
• RAD (no other cause of RAD is present)

Answer 27

Left posterior hemiblock