Bradyarrhythmias

Question 1

Main causes of bradycardia

Answer 1

Failure of either impulse initiation or impulse conduction

Question 2

MC causes of pathologic bradycardia

Answer 2

SA node dysfunction

AV conduction block

Question 3

Only reliable therapy for symptomatic bradycardia

Answer 3

Permanent pacemaking

Question 4

SA node commonly rises from

Answer 4

Right coronary artery

2nd: Left circumflex artery

Question 5

Action potentials of SA node

Answer 5

relatively depolarized membrane potential

slow phase 0 upstroke, relatively rapid phase 4 depolarization

-40 to -60 mV

Question 6

MCC of extrinsic SA node dysfunction

Answer 6

drugs

ANS influences

Question 7

Usual cause of intrinsic SA node dysfunction

Answer 7

Degenerative

Question 8

Failure to increase HR with exercise

Answer 8

Chronotropic incompetence

failure to reach 85% of predicted max HR at peak exercise or

failure to achieve Hr >100bpm or

Max HR with exercise <2 SD below than age-matched control population

Question 9

May distinguish SA node dysfunction from slow heart rates that result from high vagal tone

Answer 9

Intrinsic HR

administering propranolol 0.2 mg/kg and atropine 0.04 mg/kg

N = 117.2 - (0.53 x age) bpm

Question 10

Invasive tests for SA node dysfunction

Answer 10

SNRT (sinus node recovery time)

SACT (sinoatrial conduction time)

combination with Low IHR is a SENSITIVE AND SPECIFIC indicator of SA node dysfunction

Question 11

Class I indications for pacemaker imlantation in SA node dysfunction

Answer 11

symptomatic brady or sinus pause

symptomatic brady and unresponsive to long term medical therapy

symptomatic chronotropic incompetence

AF with brady and pauses >5s

Question 12

Persistent AV block is common

Answer 12

myocardial ischemia

aging and fibrosis

cardiac infiltrative diseases

Question 13

Most rapid conduction in the heart is observed

Answer 13

Bundle of His and bundle branches

Question 14

Wide QRS in AV block

Answer 14

Delay in distal conduction system

Question 15

Narrow QRS in AV block

Answer 15

Delay in AV node proper (or less commonly in the Bundle of His)

Question 16

Intermittent failure of electrical impulse conduction from atrium to ventricle

Answer 16

2nd degree AV block

Question 17

Slowing of conduction through AV junction

Answer 17

1st degree AV block

Question 18

Complete failure of conduction from atrium to ventricle

Answer 18

Complete or third-degree AV block

Question 19

More likely to proceed to higher grades of AV block

Answer 19

Type II 2nd degree AV block

Question 20

Class I indications for pacemaker implantation in acquired AV block

Answer 20

3rd degree or high grade AV block at any anatomic level associated with:
symptomatic brady
essential drug therapy causing symptomatic brady
asystole >3s or escape rate <40bpm while awake
post op av block not expected to resolve
cath ablation of AV junction
neuromuscular diseases

2nd degree AV block with symptomatic brady

Type II 2nd degree AV block with wide QRS

Exercise-induced 2nd or 3rd AV block without ischemia

AF with brady and pauses >5s

Question 21

Class I Indications for pacemakers in AV block with MI

Answer 21

Persistent AV block in the His/Purkinje system with bilateral BBB or 3rd degree AV block within or below rhe His after MI

Infranodal AV block and assoc BBB

Persistent and symptomatic 2nd or 3rd degree AV block

Question 22

Class I indications for pacemaker in chronic bifascicular and trifascicular block

Answer 22

Intermittent 3rd degree AV block

Type II 2nd degree AV block

Alternating BBB