Bradyarrhythmias

Question 1

3 mechanisms of arrhythmia

Answer 1

abnormal automaticity, triggered activity, reentry

Question 2

abnormal triggered activity is associated w/

Answer 2

QT prolongation, Torsades w/ early afterdepolarizations

Question 3

mechanism of Early afterdepolarizations

Answer 3

net inward plateau phase of Ca++, delayed repolarization and extra depolarization during phase 2

Question 4

mechanisms of delayed afterdepolarization

Answer 4

Ca++ overload in the cell, results from rapid rates

Question 5

2 requirements for reentry

Answer 5

two pathways, heterogenous conduction/refractory period in each pathway

Question 6

causes of bradyarrhythmias

Answer 6

abnormal automaticity or degeneration of normal conduction system

Question 7

sinus brachycardia ECG and causes

Answer 7

normal p waves and rhythm, just slow- can be caused by high vagal tone, ischemia, degenerative disease, drugs, hypothyroidism

Question 8

sinus pause, causes

Answer 8

long pause in b/w normal sinus beats, caused by degenerative disease in/around SA node- can cause syncope when longer than 3 seconds

Question 9

tachy brady syndrome, causes and Tx

Answer 9

long pauses in rhythm at end of tachyarhythmia from overdrive suppression and/or a fib

can cause syncope, Tx usually pacemaker to prevent prolonged brachycardia

Question 10

junctional escape rhythm

Answer 10

AV nodal cells takeover from dysfunctional SA node, slower rate due to slower phase 4 slope- 40s to 50s bpm

Question 11

ECG of junctional escape rhythm

Answer 11

narrow QRS, can see P waves but they can be after QRS from retrograde conduction up atria

Question 12

first degree heart block

Answer 12

every P has a QRS, but prolonged PR

Question 13

second degree heart block

Answer 13

regular P waves, not not all accompanied by QRS

Question 14

third degree heart block (total heart block)

Answer 14

constant, independent atrial and ventricular rates- no relation b/w P and QRS

Question 15

causes of first degree heart block

Answer 15

high vagal tone, degenerative disease, drugs

Question 16

differentiate type I and type II second degree AV block

Answer 16

type I:
w/i AV node- gradually prolonging PR interval until complete block, worsens w/ vagal stimulation (carotid massage) improves w/ sympathetic or anticholinergic (exercise or atropine)

type II:
below/distal to AV node, short/constant PR, wide QRS like bundle branch block, requires permanent pacing, can progress to full block

Question 17

ECG of 3rd degree block

Answer 17

constant PP, constant RR, no relationship b/w P and QRS

Question 18

treatment for 3rd degree block

Answer 18

ventricular pacing- atrial sensing and signal delivered to ventricle