Antiarrhythmics

Question 1

3 phases of SA node pacemaker potential

Answer 1

Phase 4 - pacemaker Na influx, Ca channels recover from inactivation (slow increase)
Phase 0 - Ca influx (steep upstroke)
Phase 3 - Ca channels inactivate, K efflux

Question 2

Pacemaker cell contains what channel

Answer 2

HCN channel
Simultaneous K efflux and Na influx (funny current)
Upstroke inactivates HCN

Question 3

Ventricular my pure action potential

Answer 3

0 - Na+ channels open
1 - Na+ channels close; fast K+ channels open
2 - Ca2+ channels open; fast K+ channels close
3 - Ca2+ channels close; slow K+ channels open
4 - Resting potential

Question 4

Link between sympathetic nerves and heart rate

Answer 4

Activation causes release of NA
Increased opening of HCN channels in pacemaker cells - Na+ influx
Opens Ca2+ channels
Heart rate increases

Question 5

Link between parasympathetic nerves and heart rate

Answer 5

Activation causes release of Ach
Decreases opening of HCN channels - decreased Na+ influx
Decreased Ca2+ influx
Increased K+ efflux
Hyperpolarisation
Heart rate decreases

Question 6

What is a EAD

Answer 6

Early after depolarisation
Secondary voltage depolarises during repolarising phase
Reactivated Ca2+ channels

Question 7

What are DADs

Answer 7

Delayed after depolarisation
Seen at increased heart rates
Caused by elevated Ca2+ activation of Na/K channels

Question 8

About Class 1 antiarrhythmias

Answer 8

Treat tachycardia
Na channel blocker
Lidocaine / Lignocaine
Target phase 0

Question 9

About class 2 anti arrhythmias

Answer 9

Treat tachycardia
Beta blocker
Metoprolol
Target phase 4 and 2

Question 10

About class 3 anti arrhythmics

Answer 10

Treat tachycardia
K channel blockers
Amiodarone
Target phase 3

Question 11

About class 4 anti arrhythmics

Answer 11

Treat tachycardia
Ca channel blockers
Verapamil
Target phase 2

Question 12

Drugs to treat cardiac arrest

Answer 12

Asystole - adrenaline / epinephrine
Ventricular fibrillation - amiodarone, lignocaine

Question 13

What does atropine do

Answer 13

Blocks vagal inhibition of sinus and AV node
IV bolus injection
Inc heart rate
Anticholinergic effects

Question 14

Class 1a

Answer 14

Lengthen action potential duration and refractory period
Quinidine

Question 15

Class 1b

Answer 15

Shorten action potential duration and refractory period
Ligno/Lidocaine

Question 16

Class 1c

Answer 16

No effect on action potential
Delay conduction velocity of purkinje fibres
Flecainide

Question 17

Lidocaine actions

Answer 17

Blocks fast sodium channel
Slows phase 0 depolarisation

Question 18

Lidocaine pharmacology

Answer 18

Short half life - bolus IV
Not absorbed via oral route
Hepatic clearance decreased in elderly, heart failure, liver disease

Question 19

Lidocaine adverse effect

Answer 19

Hypotension , heart block
Neurotoxicity , fits

Question 20

2 types of class 2 drugs and example

Answer 20

Non-cardio selective - propranolol
Cardioselective - atenolol

Question 21

Difference between selective and non-selective beta blockers

Answer 21

Selective block beta 1
Non selective block beta 1 and 2

Question 22

Actions of beta blockers

Answer 22

Adrenoreceptor antagonist
Reduce intrinsic rate in sinus and AV node
Reduce HR BP
Reduces renin secretion

Question 23

Beta blocker side effects

Answer 23

B1 - bradychardia
B2 - exacerbation of asthma
Other - fatigue, sleep disturbances, withdrawal

Question 24

Amiodarone indications

Answer 24

Supraventricular tachycardia
First line for ventricular fibrillation

Question 25

Amiodarone adverse effects

Answer 25

Thyroid disturbances
Hepatitis
Blue-grey skin discolouration

Question 26

3 classes of Ca2+ channel blocker

Answer 26

Dihydropyridines - amlodipine (arterial vasodilation)
Benzothiazepines - diltiazem
Phenylalkylamine - verapamil (antiarrhythmic)

Question 27

Verapamil indication

Answer 27

Supraventricular arrhythmia

Question 28

Verapamil adverse effect

Answer 28

Heart failure
Hypotension
Constipation
Vasodilation
Flushing