readings

Question 1

bradycardia cause

Answer 1

failure of sinus node function of AV conduction disturbances

Question 2

some causes of bradycardia

Answer 2

autonomic disturbances, drugs, chronic intrinsic conduction system disease, acute cardiac damage (endocarditis, infarction, etc.)

Question 3

sick sinus syndrome/sinus node dysfunction

Answer 3

increasing prevalence with age
accounts for 50% of pacemaker patients

failure of intrinsic automaticity and failure of propagation of sinus node impulses to the surrounding atrial tissue

referred to as sinus node block

Question 4

clinical presentation of sick sinus syndrome

Answer 4

persistent or episodic brady
inability to augment HR with exercise (chronotropic incompetence)
sinus pauses
or a comination

Question 5

escape mechanisms

Answer 5

competent “escape mechanisms” allow a way around the sinus node dysfunction

these patients can be asymptomatic, clinically well tolerated, and require no treatment

Question 6

sx of brady

Answer 6

fatigue, listlessness, or dyspnea
LH, pre-syncope, or syncope
exacerbates CHF

Question 7

sinus node arrest/pause on EKG

Answer 7

pause in atrial activity –> absence of P waves

pauses greater than 3 seconds = pathologic

Question 8

indications for pacemaker therapy

Answer 8

sinus pauses lasting >3 seconds
associated sx
history of sx related to bradycardia

Question 9

sinoatrial exit block

Answer 9

sinus node dysfunction –> often accompanied by significant atrial fibrosis –> impeded propagation to the atrial tissue

Question 10

EKG finding for sinoatrial exit block

Answer 10

abrupt halving of the P wave rate followed by an abrupt return to baseline sinus rate

Question 11

bradycardia-tachycardia

Answer 11

tachyarrythmia
intermittent atrial arrythmias, often with intermittent Afib, with concomitant sinud node dysfunction resulting in long pauses or symptomatic bradycardia

typical manifestation: period of asystole with after termination of Afib due to recovery of automaticity

pacemaker indication

Question 12

PR interval

Answer 12

AV conduction
first portion-start of P wave (sinus node) to the AV node (not clinically important, first portion does not change over time much with each patient)

second portion-propagation time through the AV node

last component-propagation through the bundle of His bundle and bundle branches (clinically important)

Question 13

first degree AV block

Answer 13

PR interval exceeding 0.2 s in the setting of otherwise preserved AV conduction

implies a delay in AV conduction, usually at the level of AV node or His-Purkinje system

usually asymptomatic

Question 14

second degree AV block

Answer 14

may be seen normally during sleep or in athletes
may be asymptomatic or be associated with palpitations, LH, syncope, fatigue

Question 15

second degree AV in the subnodal system (His bundle and bundle branches)

Answer 15

malignant with a tendency to progress abruptly to greater degrees of AV block with unstable or absent escape mechanisms

can progress to complete heart block/sudden death

Question 16

Mobitz Type I second degree AV block vs. Mobitz Type 2 second degree AV block

Answer 16

Type 1 - at the level of the AV node
Type 2 - below the AV node (His + bundles)

Question 17

Mobitz Type 2

Answer 17

always a reason for concern
usually preceded by the development of a fixed bundle branch block

good clinical rule: these patients will also exhibit a full bundle branch block during periods of conduction in between episodes of 2nd degree AV block

Question 18

AV nodal function improves with activity!

Question 19

infranodal blocks do not improve with exercise

Answer 19

therefore, worsen with exercise or stress (increased HR)

Question 20

2:1 AV block

Answer 20

failure of conduction every other P wave

Question 21

high degree AV block

Answer 21

second degree AV block with conduction failure of 2 or more consecutive P waves

Question 22

third degree AV block (complete heart block)

Answer 22

complete failure of the AV conduction system
atrial rate that is faster than the ventricular rate with AV dissociation

Question 23

Afib always presents as an irregular ventricular response. therefore, the finding of a slow and regular response during Afib implies that the person also has an associated complete heart block.

Question 24

supraventricular tachycardias

Answer 24

SVTs –> PSVT (paroxsymal), focal atrial tachycardia, atrial flutter, organized reentrant atrial tachycardias, Afib

Question 25

PSVT

Answer 25

manifests in young patients without structural heart disease (any point from infancy to advanced age)

presentation: recurrent tachy palpitations with abrupt onset/offset

Question 26

focal atrial tachycardia

Answer 26

patients with underlying atrial enlargement and valvular heart disease

Question 27

Afib/atrial flutter associations

Answer 27

advanced age
HTN
structural heart disease
DM
obstructive sleep apnea
pulmonary disease

carries increased risk of stroke, heart failure, and death