Heart Block

Question 1

Etiology of 1st degree AV block (9 causes)

Answer 1

Normal variant
Presence of atheroscerlosis, hypertension, DM,
Degeneration of conduction system/fibrosis congenital heart disease
CAD
Drugs
Endocrine
Inflammatory
Infiltrative
Valvular calcification

Question 2

List the different factors with possible 1st degree AV block:
CAD

Answer 2

Ischemia

Question 3

List the different factors with possible 1st degree AV block:
Drugs

Answer 3

B.B., CCB, digitalis, antiarrhythmias (I and III)

Question 4

List the different factors with possible 1st degree AV block:
Endocrine

Answer 4

Hypothyroid, Hyperthryoid, adrenal insufficiency

Question 5

List the different factors with possible 1st degree AV block:
Inflammatory

Answer 5

RF, SLE, Mixed Connective Tissue Disease (MCTD), Myocarditis

Question 6

Infiltrative

Answer 6

Amyloidosis, Sarcoidosis, Hemochromatosis

Question 7

Valvular calcification

Answer 7

Mitral, Aortic

Question 8

How do you calculate heart rate on a normal strip?

Answer 8

Each line corresponds to a number i.e. first line 300, 2nd 150, 3rd 100, 4th 75, 5th 60. If you notice the difference is the previous number divided by number of lines 100 to 75 is the 4th line so 100/4=25, 100-25=75

Question 9

Describe the Different types of 2nd Degree Heart Block

Answer 9

Mobitz I (Wencke Bach)
Mobitz II

Question 10

Describe Mobitz Type 1 (Wencke Bach) as seen on ECG

Answer 10

Progressive PR-interval prolongation prior to dropped QRS “Grouped Beats”
Narrow QRS complex
Worsens with valsalva maneuver

Question 11

Describe implications of Mobitz type I

Answer 11

Progressive lengthening from earlier arrival in relative refractory period of AV conduction
Implies impairment of AV conduction
Transient

Question 12

Describe Etiology of mobitz I

Answer 12

Everything that causes 1st degree
Digitalis toxicity
Ischemic event (Inferior MI)
Myocarditis

Question 13

Etiology of 2nd Degree AV block- Mobitz type II

Answer 13

Ischemic heart disease
Seen with acute AMI
Degenerations of conduction system

Question 14

Presentation of 2nd Degree AV block, Mobitz type II

Answer 14

PR interval uniform
Dropped beat (QRS)
P wave fails to conduct
Block occurs at the level of 
Bundle of HIS, both bundle branches
Fascicular Branches
Progressive/irreversible
WORSE PROGNOSIS if block is distal to the AV node

Question 15

Presentation of Third degree heat block (Complete heart block)

Answer 15

P waves never relate to QRS Complex
Two independent Rhythms
AV dissociation- no P waves conduct to the ventricle
Can occur above or below the AV node

Question 16

Explain complete heart block above the AV node

Answer 16

Junctional rhythm narrow QRS (rate 40-55)

Question 17

Explain complete heart block below the AV node

Answer 17

Ventricular pacemaker wider QRS (rate 20-40)

Question 18

Etiology of 3rd degree heart block

Answer 18

Ischemic, infiltrative disease 
Cardiac surgery
By-pass, valve replacement
Myocarditis
Degenerative

Question 19

Complete 3rd degree AV block

Answer 19

When the conduction of supraventricular depolarization to the ventricles is totally blocked; automaticity focus escapes to pace the ventricles at its inherent rate

Question 20

How do you treat a 3rd degree

Answer 20

Pacemaker

Question 21

What should you do on every ECG

Answer 21

Check PR interval
Increased consistently in 1st degree AV block
Progressively increases in each series of cycles with Type I
Totally variable in 3rd degree AV block
Decreased in WPW and LGL syndromes
P w/o QRS response
Wenckebach and Mobitz 2 AV blocks