Atrioventricular (AV) Blocks

Question 1

What is an AV block?

Answer 1

Impairment in conduction of impulses from atria to ventricles

Caused by drugs, infarction, ischemia, fibrosis

Question 2

First-degree AV Block

Answer 2

Noticeable PR interval prolongation for more than 0.20 seconds

Impulse traveling from atria to ventricle delayed due to slow speed

Generally asymptomatic

Question 3

Causes of First-degree AV Block

Answer 3

Enhanced vagal tone (athletes, runners)

Diseases in AV node

MI

Myocarditis

Medication/drugs

Electrolyte disturbances

Question 4

Second-degree AV Block

Answer 4

Denotes impairment in conduction of impulses from atria to ventricles

Occurs when 1+ impulse fails to reach ventricle

sx: syncope, bradycardia, irregular heart rate

Question 5

Causes of Second-degree AV Block

Answer 5

Infections

Metabolic disorders

Heart disease

Structural heart defects

Medications

Question 6

Second-degree Type 1 AV Block Tracing

Answer 6

PR interval getting progressively longer

P wave eventually blocked & no QRS complex

Visible pause where AV node recovers & cycle restarts

Question 7

Second-degree Type 2 AV Block Tracing

Answer 7

Involves both bundle branches

Distance btwn P wave & QRS gets wider

Patient needs pacemaker

Question 8

Third-degree AV Block

Answer 8

Complete heart block Blockage of all impulses Patient asymptomatic initially but body will fail to compensate sx: Brady, dizziness, chest pain, pulmonary edema, syncope, confusion

Question 9

Third-degree AV Block Tracing

Answer 9

Regular rhythms but atria & ventricles act independently P waves normal but get superimposed over QRS or T PR interval varies

Question 10

Bundle Branch Block (BBB)

Answer 10

R or L ventricle gets late depolarization QRS complex notched Causes: hypertension, infection, congenital defect, pulmonary embolism, heart disease

Question 11

Bundle Branch Block (BBB) Tracing

Answer 11

P waves & PR interval normal QRS complex wider & notched