cardio: arrhythmias

Question 1

antiarrythmic drugs: class 1a

Answer 1

sodium channel blockers - moderate:
procainamide, quinidine, disopyramide

Question 2

antiarrythmic drugs: class 1b

Answer 2

sodium channel blockers - weak:
lidocaine, mexiletine

Question 3

antiarrythmic drugs: class 1c

Answer 3

sodium channel blockers - strong:
flecainide, propafenone

Question 4

antiarrythmic drugs: class 2

Answer 4

beta blockers, block sympathetic autonomic effects:
metoprolol

Question 5

antiarrythmic drugs: class 3

Answer 5

potassium channel blockers, prolong effective refractory period:
amiodarone, sotalol

Question 6

antiarrythmic drugs: class 4

Answer 6

ccb:
verapamil, diltiazem

Question 7

antiarrythmic drugs: class 5

Answer 7

other MOA:
digoxin, adenosine, magnesium

Question 8

normal cardiac rhythm

Answer 8

originates in SA node (frequency: 60-100bpm) -> spreads through the atria and enters the AV node -> AV conduction is low (~0.15s) -> impulse propagates through His-Purkinje system -> ventricular activation complete in <0.1s

Question 9

arrhythmia

Answer 9

any cardiac depolarisation that deviates from normal rhythm
- abnormality in: site of origin of impulse, rate, regularity, conduction

Question 10

likely triggers of arrhythmia

Answer 10

ischaemia, hypoxia, acidosis, alkalosis, electrolyte abnormalities, excessive catecholamine, autonomic influence, toxicity eg. digitalis, cardiac fibre overstretch, scarred/disease tissue

Question 11

all arrhythmias result from disturbance in:

Answer 11

impulse formation/conduction, or both

Question 12

amiodarone primarily class3, but shares

Answer 12

class 1,2,4 properties and additional actions

Question 13

sotalol primarily class 3, but also

Answer 13

class 2

Question 14

aim of antiarrhythmics pharmacology

Answer 14

• reduce ectopic pacemaker activity
• modify conduction/refractoriness in re-entry circuits to disable circus activity

Question 15

MOA of sodium channel blockers

Answer 15

• local anesthesia action blocking sodium channels
• reduce sodium current, slows upstroke of action potential, hence slows conduction

Question 16

flecainide moa

Answer 16

(class 1c) blocks sodium and potassium channels, no anti-muscarinic effects

Question 17

flecanide use

Answer 17

pt w normal hearts with supraventricular arrhythmias
X aflutter, ihd, structural heart disease, hfref, liver disease, crcl<35

Question 18

flecainide toxicity

Answer 18

may cause severe exacerbation of arrhythmia in patients with pre-existing ventricular tachyarrythmias or previous MI

Question 19

disopyramide MOA

Answer 19

(class 1a)
- blocks sodium channels, slow upstroke of action potential
- nonspecifically blocks potassium channels, prolongs action potential

-> slows conduction
-> directly depresses sa and sv node

extracardiac effects:
- ganglion blocking activities, hence reduce peripheral vascular resistance -> produce hypoTN esp w iv use

Question 20

amiodarone MOA

Answer 20

(class 3) prolongs action potentials
- usually by blocking K channels or
- sometimes by enhancing inward current eg. thru sodium channels (block sodium channels)
- also weak adrenergic and ccb

-> prolongs action potential duration
-> slow hr and av node conduction

extracardiac effects: produce peripheral vasodilation

Question 21

dronedarone is a ____ of amiodarone

Answer 21

structural analogue, lacks iodine atoms
- less toxic but less effective alternative
- no thyroid and pulmonary toxicity

Question 22

amiodarone use

Answer 22

treatment of serious ventricular arrhythmias, effective for supraventricular arrhythmias eg. AF

Question 23

amiodarone toxicity

Answer 23

• bradycardia
• heart block in pt w existing SA/AV node disease
• fatal pulmonary fibrosis in 1% of pt
• hepatitis
• tissue accumulation: blue-grey skin discoloration, corneal microdeposits
• hypo/hyperthyroidism (source of inorganic iodine)

Question 24

digoxin MOA

Answer 24

• positive inotropic effects: blocks Na-K ATPase, incr intracellular myocytes Na and hence Ca influx
• negative chronotropic effects: decreases conduction of electrical impulses through the av node inhibition and increases vagal activity

Question 25

adenosine MOA

Answer 25

used iv for terminating SVT
- acts on adenosin receptors (GPCRs) -> influence potassium channels -> ca channels -> inhibit avail of ca in cells -> decr hyperexcitability and propagation of signals involved in AF

Question 26

magnesium sulphate/trimagnesium dicitrate (anhydrous) used for

Answer 26

specific arrhythmias eg. torsades de pointes and digoxin-induced

Question 27

moa of magnesium

Answer 27

exact unclear: Mg competes with Ca in terms of uptake and distribution of Ca within cells

Question 28

arrhythmias, hr<60

Answer 28

Bradycardia: heart block, simple bradycardia
- atropine, adrenaline, dopamine

Question 29

Arrhythmias, hr>100, QRS<120ms

Answer 29

Narrow complex (info propogated through AV node into purkinje complex = supraventricular issue):
- AF/flutter: class 3, 1c - or rate control by nodal blocking agents eg. Class 2/4
- Other SVTs: class 2/4
- Sinus tachycardia (MI or anxiety): class 2

Question 30

Arrythmias, hr>100, qrs>120ms

Answer 30

Broad complex:
- VF: after 3x defibrillation attempts - vasopressin, adrenaline, amiodarone
- VT: amiodarone, class 1b

Question 31

Supraventricular preexcitation tachycardias of the Wolff-Parkinson-White syndrome

Answer 31

AV node inhibitors (class 2/4) or by catheter ablation of the bypass tract

Question 32

Arrhythmias of congestive heart failure

Answer 32

Class 2: carvediolol
Class 5: digoxin

Question 33

Sustained ventricular tachycardia especially with infarcted or ischemic zone

Answer 33

Cardioversion if persistent or amiodarone

Question 34

Drugs that can cause prolonged QT interval

Answer 34

Antiarrythmics: disopyramide, procainamide, quinidine, amiodarone, sotalol
Anaesthetics: halothane
Antibiotics: macrolides, metronidazole with alcohol, moxifloxacin
Antifungals: ketoconazole, fluconazole
Antivirals: nelfinavir
Antimalarials: chloroquine, mefloquine
Antipsychotics
Antihistamines: terfenadine, astemizole
Antidepressants: amitriptyline