6.1 cardiac arrhythmia drugs

Question 1

what are cardiac arrhythmias?

Answer 1

heart conditions where rate/timing of contractions are insufficient to maintain normal cardiac output

Question 2

how is
- Na
- K 
- Ca 
distributed across a cell membrane?

Answer 2

Na conc is higher outside the cell
K conc is higher inside the cell
Ca conc higher outside the cell

Question 3

what is the effect of class 1 drugs on the cardiac action potential? give 2 examples.

how will it affect an ECG?

Answer 3

Na channel blockers e.g Lidocaine and Flecainide

they block sodium channels so the upstroke of the AP is shifted = slower conduction throughout tissue

no effect in normal ECG but In a fast beating or ischaemic ECG, they will increase the length of the QRS complex

Question 4

what is the effect of class 2 drugs on the cardiac action potential? name an example.

Answer 4

B blockers e.g Bisoprolol

block influx of Ca into myocyte
therefore increase refractory period = takes longer for depolarisation to occur and for another AP to start

Question 5

what is the effect of class 3 drugs on the cardiac action potential? name two examples.

Answer 5

K channel blockers e.g amiodarone, sotalol

increase the length of the refractory period in AV node and myocyte and the duration of the action potential aka prolong depolarisation and AV conduction

also increase threshold potential

Question 6

what is the effect of class 4 drugs on the cardiac action potential? give two examples.

Answer 6

Ca channel blockers e.g verapamil, diltiazem

decrease inward Ca currents, resulting in a decrease of spontaneous depolarisation and increased refractory period in the sa NODE

Question 7

how do Ca channel blockers affect the action potential in the AV node?

Answer 7

they increase the length of the refractory period

also takes longer for the cell to depolarise = slower conduction velocity (due to longer slope)

Question 8

how does adenosine affect the action potential in the AV node?

Answer 8

adenosine
binds to A1 receptors= activated K currents in AV and DS note = decreases action potential duration and HR = slows AV condctipm

good for convert re entrant supraventricular arrhythmias and diagnosis of coronary artery disease

Question 9

how do B agonists affect the action potential in the AV node?

Answer 9

they increase the amount of Na and K entering the cell = decreases the length of the funny potential

Question 10

what is an ectopic focus arrhythmia?

Answer 10

AP rises from sites other than the SA node

Question 11

what is the difference between delayed after depolarisation and early afterdepolarisation?

Answer 11

delayed after depolarisation
- get depolarisation arising from the resting potential

early after depolarisation
- arises from the plateau which is prolonged

Question 12

what s a conduction block?

Answer 12

when the impulse is not conducted from the atria to the ventricle

Question 13

what is re-entry conduction?

Answer 13

1) a pathway is blocked
2) so, impulse from this pathway has to loop round and go backwards
3) so the cells here will be re-excited

Question 14

what is wolf Parkinson white syndrome?

Answer 14

there is an accessory pathway in the heart called the bundle of Kent in some people, presents in only small populations

get heart arrhythmia’s

Question 15

why do arrhythmia’s occur?

Answer 15

• automatic or triggered activity

- reentry due to scar, anatomy of AV node slow and fast pathway/ Wolf Parksinson White

Question 16

what are the side effects of class 1 drugs?

Answer 16

dizziness, drowsiness, abdominal upset

Question 17

how will class 2 drugs effect an ECG?

Answer 17

increase PR interval and decrease heart rate

Question 18

what are the Side effects of class 2 drugs?

Answer 18

bronchospasms
hypotension

don’t use in partial av block or acute heart failure (as used in stable heart failure)

Question 19

how to class 3 drugs affect an ECG?

Answer 19

Increase length of
- PR
- QRS
- QT
intervals 

and decrease heart rate

Question 20

what are the side effects of class 3 drugs?

Answer 20

pulmonary fibrosis
hepatic Injury
increased LDL cholesterol
thyroid disease
photosensitivity 
optic neuritis 

increase with time

may need to reduce dose of digoxin and monitor warfarin more closely

NB: amidarone has the greatest efficacy, but the greatest side effects

Question 21

how do class 4 drugs affect an ECG?

Answer 21

increase PR interval

HR can increase or decrease dependant on blood pressure and baroreceptor reflex

Question 22

what are the side effects of class 4 drugs?

Answer 22

caution when partial AV block is present - can get systole if B blocker is on board.

Caution when hypotension decreased cardiac output or sick sinus

some GI problems e.g constipation

Question 23

how does digoxin aid arrhythmias?

Answer 23

its a cardiac glycoside

will enhance vagal activity(increase K decrease Ca and increase refractory period0

this will slow AV conduction and HR
good for atrial fibrillation and flutter

Question 24

which IV drugs can be used for ventricular tachycardia?

Answer 24

• bisoprolol

- amidorone (via central line)

Question 25

what drugs can be used in AF?

Answer 25

rate control

• bisoprolol
• verapamil
• digoxin

rhythm control

• sotalol
• bisoprolol
• amidarone

Question 26

should flecainide be used alone in atrial flutter?

Answer 26

no

give AV node blocking drugs to reduce ventricular rates in atrial flutter

Question 27

what are the best drugs for treatment of wolf Parkinson white syndrome?

Answer 27

flecainide

amidarone

Question 28

what drugs can be used in re entrant SVT?

Answer 28

acute

• adenosine
• verapamil
• flecainide

chronic

• bisoprolol, verapamil
• sotalol
• flecainide
• amidarone

Question 29

what drugs are used for ectopic beats?

Answer 29

bisoprolol first line

flecainide, sotalol or amidarone

Question 30

what drugs would you use to treat sinus tachycardia?

Answer 30

bisoprolol, vermpail