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CPTP 2 > CPTP antiarrhyth > Flashcards

CPTP antiarrhyth Flashcards

1
Q

Describe the cardiac action potential cycle

A

Phase 4 - spontaneous diastolic drift. Na+&Ca2+ entry. SAN, AVN and Purkinje

Phase 0 - Na+ channel opens at threshold potential. Fast Na+ entry. Na+ channel closes as potential less negative

Phase 1/2 - Slow Ca2+ entry

Phase 3 - K+ exit

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2
Q

Causes of arrhythmia

A

Abnormal impulse generation

  • abnormal pacemaker activity
  • triggered activity

Abnormal impulse conduction

  • heart block
  • re-entry phenomenon (re-excitation of a region of the heart by a single electrical impulse)
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3
Q

Types of bradyarrhythmia (slow HR)

A

Sinus bradycardia

Nodal/ junctional bradycardia (caused by the absence of the electrical impulse from the sinus node)

Heart block (1st, 2nd and 3rd)

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4
Q

Drugs to treat bradycardia

A

Atropine
Isoproterenol
Pacing

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5
Q

Atropine

mechanism of action

A
  • Naturally occurring antimuscarinic alkaloid
  • Blocks vagal inhibition of Sinus and AVN
  • IV bolus administration
  • Predominantly hepatic metabolism
  • Short half-life
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6
Q

Atropine side effects

A

anticholinergic adverse effects

  • dry mouth
  • mydriasis
  • postural hypotension
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7
Q

Isoproterenol (isoprenaline)

mechanisms of action

A
  • B1/2 adrenoceptor agonist
  • Positive chronotropic effect, esp. Sinus node
  • Short half-life requiring IV infusion (also first pass metabolism)
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8
Q

Isorpoterenol side effects

A

Sympathomimetic adverse effects

  • tachycardia
  • arrhythmias
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9
Q

Types of tachyarrythmias (fast HR)

A

Supraventricular tachycardia (SVT)

Ventricular tachycardia (VT)

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10
Q

Describe SVT

A
  • Sinus or nodal tachycardia
  • Accessory pathway re-entrant tachycardias
  • Atrial fibrillation or flutter
  • Narrow complex
  • Arise in SAN, atria or AVN
  • Not usually life-threatening
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11
Q

Describe VT

A

-Can be monomorphic/ polymorphic

  • Broad complex
  • Arise in Purkinje fibres or ventricle
  • Can cause cardiac arrest
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12
Q

Antiarrhythmic drugs classification

A

Class I
local anaesthetics/ sodium channel blockers/ membrane stabilisers/ inhibit phase 0 depolarisation

Class II; antisympathetic drugs

Class III; potassium channel blockers, inhibit phase III repolarisation

Class IV; Calcium channel blockers, inhibit Ca-dependent depolarisation

Class V
cardiac glycosides (vagolytic)
adenosine (antipurinergic)
magnesium sulphate

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13
Q

Class 1a

effect on action potential duration and examples

A

Lengthen action potential duration and refractory period

Quinidine, propafenone, disopyramide

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14
Q

Class Ib

effect on action potential duration and examples

A

Shorten action potential duration and refractory period

Lignocaine, lidocaine

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15
Q

Class Ic

effect on action potential duration and examples

A

no effect on action potential duration and refractory period.
Delay coinduction velocity in Purkinje fibres

Flecainide

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16
Q

Class Ib - lidocaine

actions

A

blocks fast sodium channels and slows phase 0 depolarisation

shortens action potential duration

specific effect on rapidly depolarising tissue (use-dependent effect)

17
Q

lidocaine pharmacokinetics

A
  • Short half-life (must be given IV)
  • Not absorbed via oral route (hepatic first pass metabolism
  • Hepatic clearance decreased in elderly, heart failure, liver disease
18
Q

lidocaine side effects

A

hypotension, heart block

neurotoxicity, fits

19
Q

Class II drugs

A

Beta blockers

  • non-cardioselective; propranolol
  • cardioselective (B2); Atenolol

Others
Bretyllium (BP lowering drugs)

20
Q

Class III drug

A

e. g. amiodarone
- prolongs action potential duration and refractory period
- lengthened QT interval on ECG
- Long half-life
- Hepatic metabolism

21
Q

Amiodraone side effects

A
  • thyroid disturbances
  • pulmonary fibrosis
  • pro-arrhythmia and torsade de pointes
  • peripheral neuropathy
  • hepatitis
  • blue-grey skin discolouration
22
Q

CCB

A

Dihydropyridines
e.g. nifedipine, amlodipine
arterial vasodilation

Benzothiazepines
e.g. diltiazem
mixed vascular and cardiac effects

Phenylalkylamine
e.g. verapamil
negative inotrope and chronotrope, antiarrhythmic

23
Q

cardiac glycoside
example
actions
indications

A

e. g. digoxin
- antiarrhythmic; vagotonic effect reduces rate and conduction velocity in sinus and AVN
- inotropic-increases intracellular Ca2+

CPTP 2 (12 decks)

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