C244: BRADYARRHTYMIAS: DISORDERS OF SA NODE

Question 1

____________sinoatrial (SA) node serves as the natural pacemaker of the heart

Answer 1

sinoatrial (SA) node serves as the natural pacemaker of the heart

Question 2

If the sinus node is dysfunctional or suppressed a subsidary pacemaker in the ________ or ________ will take over leading to a slower junctional or ventricular rhythm

Answer 2

If the sinus node is dysfunctional or suppressed a subsidary pacemaker in the atrioventricular node or specialized conduction system will take over leading to a slower junctional or ventricular rhythm

Question 3

Once irreversible sinus node dysfunction is confirmed, ________the only reliable therapy for symptomatic bradycardia.

Answer 3

Once irreversible sinus node dysfunction is confirmed, permanent pacemaker implantation is the only reliable therapy for symptomatic bradycardia.

Question 4

LOCATION OF SA NODE:

Answer 4

the sulcus terminalis on the epicardial surface of the heart at the right atrial–superior vena caval junction

Question 5

Action potential depolarization in the SA node is normally at a resting rate of ________beats/min.

Answer 5

Action potential depolarization in the SA node is normally at a resting rate of 60–100 beats/min.

Question 6

The autonomic nervous system exhibits control over the sinus node, with a preponderance of ________ innervation at baseline

Answer 6

The autonomic nervous system exhibits control over the sinus node, with a preponderance of parasympathetic innervation at baseline

Question 7

Cells in the SA node exhibit the most rapid phase ________depolarization and thus are the dominant pacemakers in a normal heart.

Answer 7

Cells in the SA node exhibit the most rapid phase 4 depolarization and thus are the dominant pacemakers in a normal heart.

Question 8

Unlike atrial and ventricular cells, sinus node pacemaker cells have no true resting potential, but instead depolarize automatically and repetitively after the end of an action potential. True or False…

Answer 8

True

Question 9

depolarizing current in the SA node myocytes results primarily from slow ________currents instead of fast________channels, which are absent in SA node cell

Answer 9

depolarizing current in the SA node myocytes results primarily from slow calcium currents instead of fast sodium channels, which are absent in SA node cell

Question 10

Spontaneous phase 4 depolarization results from a combination of (3)

Answer 10

1. slow inward depolarizing sodium currents (i f , “funny currents”)
2. T-type calcium channel
3. L-type calcium channel

Question 11

Phase 0 is the ________ phase of the action potential

Answer 11

Phase 0 is the depolarization phase of the action potential

Question 12

Intrinsic heart rate declines________ beats/min for each decade of age.

Answer 12

Intrinsic heart rate declines 5–6 beats/min for each decade of age.

Question 13

Intrinsic sinus node disease is sometimes referred to as _______

Answer 13

sick sinus syndrome or sinus node dysfunction (SND)

Question 14

Correlation between sleep apnea and bradyarrythmia:

Answer 14

Many patients with sleep apnea will have high vagal tone during sleep and especially during apneic events. Sinus bradycardia and sinus pauses frequently are seen

Question 15

Formula for intrinsic heart rate:

Answer 15

118.1 – (0.57 × age)

Question 16

SA nodal dysfunction subtyprs (6)

Answer 16

1. Sinus node exit block
2. Tachy-brady syndrome
3. Chronotropic incompetence
4. Sinus node fibrosis
5. SA nodal ischemia and infarction
6. Carotid sinus hypersensitivity and neurally mediated bradycardia

Question 17

results from failure of impulse formation within the sinus node

Answer 17

sinus arrest

Question 18

Type of sinus node exit block that involves progressive delay THEN intermitten failure to propagate to the atriu

Answer 18

Mobitz I SA block

Question 19

Type of sinus node exit block that involves FIXED delay THEN intermitten failure to propagate to the atrium

Answer 19

Mobitz II SA block

Question 20

This type of SA exit block can be inferred on the ECG if the sinus rate abruptly transitions to a sinus rate that is half the previous rate (every other sinus depolarization is blocked from exiting to the atrium)

Answer 20

Mobitz II SA block

Question 21

This type of SA exit block can be inferred on the ECG in the setting of progressive shortening of the P-P interval leading up to a sinus paus

Answer 21

SA Wenckeback (type I)

Question 22

Type of SA nodal dysfunction consisting of high heart rates (most commonly atrial fibrillation) with alternating symptomatic bradycardia or offset pauses

Answer 22

Tachy-Brady Syndrome

Question 23

Type of SA nodal dysfunction consisting of high heart rates (most commonly atrial fibrillation) with alternating symptomatic bradycardia or offset pauses

Answer 23

Tachy-Brady Syndrome

Question 24

Inability of the heart to increase its rate to meet activity or demand

Answer 24

Chronotropic incompetence

Question 25

Pacing nomenclature… what do the 4 letters represent

Answer 25

1. First letter - chamber paced
2. Second letter - chamber sensed
3. Third letter - response to sensed event
4. Fourth letter - rate response is turned on

Question 26

What is RATE RESPONSE

Answer 26

essential for the treatment of CI as it attempts to mimic the natural physiologic increase in heart rate in response to exertion.

Question 27

Single chamber atrial pacemaler could be used in what condition

Answer 27

pure sinus node dysfunction

Question 28

Indicatons for permanent pacing in sinus node dysfunction (5)

Answer 28

Question 29

CLASS I INDICATION for pacing

Answer 29

1. documented symptomatic bradycardia
2. SND-associated long-term drug therapy for which there is no alternative
3. Symptomatic CI

Question 30

CLASS IIA INDICATION for pacing

Answer 30

1. those outlined previously in which SND is suspected but not documented
2. for syncope of unexplained origin in the presence of major abnormalities of SA node dysfunction

Question 31

CLASS IIB INDICATION for pacing

Answer 31

Mildly symptomatic individuals with heart rates consistently <40 beats/min constitute a class IIb indication for pacing

Question 32

Refers to rotation of the pacemaker pulse generator in its SQ pocket, either intentionally or inadvertently

Answer 32

Twiddler’s syndrome

Question 33

ANTI HTN MEDS THAT CAN CAUSE SINUS NODE DYSFUNCTION

Answer 33

• Beta blockers
• Clonidine
• Methyldopa
• Non-DHP CCBs