Antiarrhythmics

Question 1

Phase 0

Answer 1

Rapid Depolarization (ventricular contraction)

• increased NA conductance (channels open) through FAST channels (-70 mV)
• end w/ Na channels “inactive” @ +65 mV

Question 2

Phase 1

Answer 2

Early Rapid Repolarization

• Na channels closed, inactivated
• K channels open, begin transient efflux of K to “reset” voltage. (rapidly inactivated)

Question 3

Phase 2

Answer 3

• Plateau
• via calcium influx through SLOW channels (L & T type channels)
• K channels still open, maintain plateau through K+ efflux
• voltage = +10 to -20 mV

Question 4

Phase 3

Answer 4

Rapid Repolarization

• lots of K movement
• No significant movement of Ca or Na

Question 5

Phase 4

Answer 5

Spontaneous Depolarization

• slow depol. characteristic of all pacemaker cells
• interaction of outward Ca and inward K during diastole
• ATP dependent pumps move ions to regain balance

Question 6

Slow channels, calcium mediated

Answer 6

• responsible for phase 0 in SA and AV noes (slow conduction velocity
• contribute to phase 2 in ventricular contractile cells (prolongs refractory period)
• affects phase 4 spont. depol
• facilitates catecholamines (cAMP)

Question 7

Fast channels, Na mediated

Answer 7

• phase 0 (rapid, sharp upstroke in His-Purkinje and atrial and ventricular muscle
• rapid conduction velocity

Question 8

Automaticity

Answer 8

impulse generation

Question 9

T/F: Cells that undergo spontaneous phase 4 depol are automantic anc capable of impulse generation

Answer 9

True,

Factors that reduce automaticity at the higher pacemaker sites will passively favor movement of pacemaker to lower site

Question 10

Ectopic Foci result from…

Answer 10

• enhanced automaticity at a site outside the SA node
• SNS influences, hypercarbia, hypoxia, dig tox
• ex.) A.Fib - little cells just firing on their own, increased clot risk

Question 11

Re-Entry

Answer 11

-circles around pacemaker sites to generate new paths

Question 12

Na Channel impulse generation…

Answer 12

Atria

Ventricles

Question 13

Ca Channel impulses generate…

Answer 13

SA node

AV node

Question 14

Amiodarone and anticoags

Answer 14

increase bleed risk, increased INR

Question 15

Amiodarone and meds that prolong QT interval

Answer 15

Torsades de Pointes

Question 16

Amiodarone and Digoxin

Answer 16

increased dig toxicity

Question 17

Amiodarone and lidocaine

Answer 17

increased lidocaine toxicity

Question 18

amiodarone and statins

Answer 18

increase myalgias

Question 19

amiodarone and midazolam

Answer 19

prolonged sedation, increased risk of resp depression

Question 20

amiodarone and suggamedex

Answer 20

increased risk of bradycardia, additive effect

Question 21

amiodarone and AV nodal blockers

Answer 21

increased risk of bradycardias, sinus arrest, AV block

Question 22

Prodysrhythmic Effects

Answer 22

brady or rachy that represent new cardiac dyrrhythmias associated w/ chronic antidysrhythmic tx

ex. torsades, increased ventric tachy’s, wide complex vent. rhythm

Question 23

Torsades de Pointes

Answer 23

K channel blockade may prolong QT interval and induce triggered activity in ventricle –> polymorphic VT or VF

-occurs in 1-8% of pts recieving QT prolonging drugs
will develop torsades

Question 24

Which class blocks potassium channels and prolongs QTc interval

Answer 24

Class 1A and Class 3

Question 25

QT Prolonging Meds

Answer 25

``` Class 1A and Class 3 antiarrhythmics, antipsychotics (haldol, geodon, risperdal), diuretics, antifungals, antibiotics (macrolides and FQ's), antidepressants, antinausea, methadone, aricept, volatile anesthetics ```

Question 26

QT Prolonging States

Answer 26

``` >65 y.o. bradycardia, genetic predisposition low K, Mg or Ca female heart dx QTc > 60 ms compared to pretreat or > 500 ms recent cardioversion DM2, hypothyroid, low temp ```

Question 27

Tx of QT prolong brady

Answer 27

magnesium chemical pacemaker - isoproterenol lidocaine (ventric arrhythmia)

Question 28

Incessent V. Tach

Answer 28

- precipitated by 1A and 1C - slow impulses to that ventricular reentry drives vtach (reentry) - more likely with poor LV fx

Question 29

Wide Complex V. Rhythms

Answer 29

- flecainide (1C) use with structural heart disease | - usually from high levels or quick change