Bradycardia

Question 1

2 main causes of bradycardia (<60 bpm)

Answer 1

1. insufficient impulse formation (sinus node dysfunction)
2. insufficient impulse conduction (AV block)

Question 3

SSS s

Answer 3

sick sinus syndrome– symptoms due to sinus node dysfunction (not every bradycardia is bad). Sinus pauses and sinus arrest, or inappropritate HR response to exertion.

Question 4

SSS is associated with 3 things

Answer 4

1. ectopic atrial rhythms, junctional rhythm
2. AV block
3. atrial tachyarrthmias– AF and atrial flutter.

Question 5

a sinus pause is commonly seen in normal people while ___ but it’s abnormal while ____

Answer 5

a sinus pause is commonly seen in normal people while SLEEPING but it’s abnormal while AWAKE

Question 6

symptoms of SSS or bradycardia in general

Answer 6

• intermittent syncope and presyncope, dizzieness ,light headedness, falls i nthe elderly, palpitations.
• fatigue
• dyspnea and eercise intolerance.

Question 7

how do you diagnose SND (sinus node dysfunction)

Answer 7

record inappropriately slow sinus rate on ECG. may need to do it on ECG

Question 8

how do you diagnose SSS?

Answer 8

• record inappropriately slow sinus rate during symptoms.
• SYMPTOM RHYTHM CORRELATION ON ECG.
• this can be very difficult to achieve. diagnosis can be a judgement call. based on available evidence.

Question 10

“Chronotropic incompetence”:

Answer 10

inadequate heart rate in response to metabolic demand. Failure to achieve 80% of age predicted HR (220-16e)

• is another feature of snius node dysfunction.

Question 11

for primary sinus node dysfunction, the main cause is:

Answer 11

disease affecting the SAN like age/fibrosis, or paroxysmal AF“tachy-brady syndrome”, coronary disease, infiltrative diseases (sarcoid, amyloid)

Question 12

causes of secondary sinus node dysunction

Answer 12

• drugs (beta blockers, calacium channel blockers, digoxin, amiodarone, autonomic issues (carotid hypersensitivity, vasovagal syncope), hyperkalemia

Question 13

SSS treatment

Answer 13

1. revesre the reverseible cuases – reduce the rate-limiting dugs if you can.
   - check to see if they’re not hypothyroid or marked electrolyte disturbances.
2. permanent pacemaker.
3. beware vasovagal syncope: can be profound sinus pauses and bradycardia– almost never requires a permanent pacemaker.

Question 14

tachy-brady syndrome:

combination of ____ ___ and ____ conversion pauses at the termination of AF.

Answer 14

combination of paroxysmal AF and at other times, bradycardia (conversion pauses)

Question 15

how do you treat tachy-brady syndrome?

Answer 15

tachycardia treatment: rate limiting or antiarrhthmic drugs. these will likely make the brady cardia worse.

• bradycardia treated with permanent pacemakers.

Question 16

SND summary

Question 17

note

Question 18

first degree AV block

Answer 18

• just an AV delay. the PR interval is longer than nomral (>200ms). EVERY P WAVE conducts to the ventricles, just slowly.

Question 19

third degree of AV block

Answer 19

• complete AV block/complete heart block. No P wave conducts to the venricles, not even one.

the atria and ventricles are not communicateing at all- they are dissociated from each other. they might both be regular but one isn’t conducting/controlling the other.

 Some rhythm is driving the atria
 sinus rhythm, sinus tachycardia, sinus
bradycardia, atrial fibrillation etc

 Hopefully, some other rhythm is driving the ventricles
 junctional escape rhythm, ventricular escape
rhythm, paced rhythm

Question 20

Answer 20

AV complete heart block. third degree. the P waves are regular and the QRS complexes are normal but one is not causing the other.

 Sinus rhythm (70 bpm), with third degree
(complete) AV block and a junctional
escape rhythm (39 bpm)

Question 21

JVP changes in heart block

Answer 21

cannon A waves

Question 22

note: second degree AV block

Question 23

Type I second degree block (mobitz I)

Answer 23

the PR interval gradually lengthens before the P wave blocks, and the cycle begins agaain. this can be normal.

Sinus rhythm with 3:2 AV Wenckebach

Question 24

Mobitz type II second degree heart block

Answer 24

Type II (aka Mobitz II)
 The PR interval remains constant before a
P wave blocks, and the cycle begins again-- but still, some beats get "dropped"

Question 25

Where is the block?

 First degree AVB: slow
conduction can be in either the ___ or __

 2nd degree AVB, type I: usually __

 2nd degree AVB, type II: usually __

 Third degree AVB: can be __

Answer 25

 First degree AVB: slow
conduction can be in either the AVN or HP

 2nd degree AVB, type I: usually AVN

 2nd degree AVB, type II: usually HP

 Third degree AVB: can be either

Question 26

A block in the ___ node/system is more dangerous than block int he ____ because the ___ ____ are less reliable.

Answer 26

a block in the HP system is more dangerous than a block in the AVN becauase the escape thythms are less reliable.

• type II second degree is thus more dangerous than Type I second degree.
• a pacemaker should be considered even for asymptomaic type II second degree AVB

Question 27

Note; first degree AV block is almost always asymptomatic unless there’s markedly prolongeed PR interval.

Question 28

diagnosis of AVB

Answer 28

 Same as for SND: gold standard is symptom-rhythm correlation

 Can be intermittent and difficult to
diagnose

 Holter monitoring and event recorders
may be required

 Exercise testing can be useful to look for
changes in conduction with increased
sinus rate

Question 29

primary cause of AVB

Answer 29

similar to SND. disease affecteing the AV conduction system like age/fibrosis, infiltrative disease.

• also CAD (esp acute inferior MI), drugs (beta blockers, calcium channel blockers, digoxin, amiodarone), autonomic (carotid hypersensitivty, vasovagal syncope)

Question 30

types of drugs that can cause AVB

Answer 30

(beta blockers, calcium channel blockers, digoxin, amiodarone)

Question 31

Answer 31

3rd degree AVB during a stemi.

 Sinus rhythm with 3rd degree AV block
and junctional escape rhythm  Acute inferoposterior MI

Question 32

3rd degree AVB in acute inferior MI

• usually repsonse to ___
• usually gets better within hours and is almost never permanent.

Answer 32

usually repsonse to atropinea

Question 33

AVB treatments

Answer 33

Question 34

AVB summary

Question 35

61-yr-old female with cirrhosis & aortic valve disease

Answer 35

3rd degree (complete) heart block

Question 36

Answer 36

2nd degree Mobitz type II AV block, then 2:1 conduction

Question 37

Answer 37

1st degree heart block

Question 38

Answer 38

2nd degree Mobitz type I AV block

Question 39

RBBB and
LBBB are
evidence of
disease below
the __.

Answer 39

RBBB and
LBBB are
evidence of
disease below
the AVN.

Question 41

characteristic finding in which leads for RBBB

Answer 41

RBB: V1: RSR’

V6: lengthened S

Question 42

characteristic findings in LBBB ECG

Answer 42

• normal sinus rhythm but dominant R wave in the left-sided leads : I, avL, V6

Question 43

type of pacemaker?

Answer 43

DDD

Question 44

type of pacemaker?

Answer 44

atrial pacing (AAI)

Question 45

type of pacemaker?

Answer 45

ventricular pacemaker. VVI