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2. Cardiovascular System > 42. Arrhythmia Therapy > Flashcards

42. Arrhythmia Therapy Flashcards

1
Q

What is an arrhythmia?

A

any deviation from the normal rhythm of the heart

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2
Q

What are different types of arrhythmias? (4)

A
  1. Sinus arrhythmia (changes in vagal tone in the respiratory cycle)
  2. supraventricular arrhythmia ( atrial fibrillation and supraventricular tachycardia; junctional)
  3. Ventricular arrhythmia (ventricular tachycardia and ventricular fibrillation)
  4. heart block
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3
Q

What happens in atrial or ventricular fibrillation?

A

Irregular, disorganised electrical signals making heart chamber quiver which can often lead to clots, stroke or heart failure

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4
Q

What is the relative charge inside the cardiac cell compared to outside the cell?

A

Inside cardiac cell, there is a negative charge relative to the charge outside the cell

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5
Q

How does resting membrane potential arise in terms of ion distribution?

A
  • results in uneven distribution of ions (na, k, ca) across cell membrane
  • an energy requiring pump is needed to maintain this uneven distribution of ions
  • sodium-potassium ATPase pump needed
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6
Q

Describe how an action potential is created in a cardiac cell.

A
  • change in distribution of ions causes cardiac cells to become excited
  • movement of ions across cardiac cell’s membrane results in the propagation of an electrical impulse
  • this electrical impulse leads to contraction of myocardial muscle
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7
Q

What happens during phase 0 of action potential in a cardiac cell?

A
  • Na enters cell

- depolarisation occurs

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8
Q

What happens during phase 1 and 2 of action potential in a cardiac cell?

A
  • Ca enters cells
  • initiation of contraction occurs
  • phase 1: rapid inactivation of na channels and opening and closing of k channels letting some k out
  • phase 2: l type Ca channels open
  • known as Pletau phase
  • no Plateau phase present in pacemaker cells action potentials
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9
Q

What happens during phase 3 of action potential in a cardiac cell?

A
  • K exits the cells (K channels open)
  • L-type Ca channels close
    -repolarisation
    -
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10
Q

What happens during phase 4 of action potential in a cardiac cell?

A
  • refractory period
  • no APs produced
  • -90mV
  • due to leaky K channels (which resets na channels for next AP)
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11
Q

What happens to K, Ca and Na throughout an AP in a cardiac cell?

A
  • K leaves the cell (from 150mM to 4mM)
  • Ca enters cell (from 2.5mM to 0.0001mM)
  • Na enters cell (from 145mM to 20mM)
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12
Q

What is the Vaughan-Williams classification of drugs used to treat arrhythmias categorised as?

A
  • Class 1 (1a,1b, 1c)
  • Class 2
  • Class 3
  • Class 4
  • Other
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13
Q

What is the electrophysiologic property of class 1a drugs for arrhythmia?

A

Fast sodium-channel blockade

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14
Q

What is the electrophysiologic property of class 1b drugs for arrhythmia?

A

Intermediate sodium channel blockade

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15
Q

What is the electrophysiologic property of class 1c drugs for arrhythmia?

A

slow sodium channel blockade

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16
Q

What is the electrophysiologic property of class 2 drugs for arrhythmia?

A

B-adrenergic receptor antagonism (blocks adrenergic receptors)

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17
Q

What is the electrophysiologic property of class 3 drugs for arrhythmia?

A

prolong refractoriness

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18
Q

What is the electrophysiologic property of class 4 drugs for arrhythmia?

A

calcium channel blockade

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19
Q

What are drug examples of class 1a for arrhythmias? (3)

A
  1. quinidine
  2. procainamide
  3. disopyramide
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20
Q

What are drug examples of class 1b for arrhythmias? (4)

A
  1. lidocaine
  2. mexiletine
  3. tocainide
  4. phenytoin
21
Q

What are drug examples of class 1c for arrhythmias? (3)

A
  1. flecainide
  2. propafenone
  3. encainide
22
Q

What are drug examples of class 2 for arrhythmias? (3)

A
  1. atenolol
  2. bisoprolol
  3. propranolol
23
Q

What are drug examples of class 3 for arrhythmias? (3)

A
  1. amiodarone
  2. bretylium
  3. sotalol
24
Q

What are drug examples of class 4 for arrhythmias? (2)

A
  1. diltiazem

2. verapamil

25
Q

What are the general properties of class 1 drugs?

A
  • membrane stabilising agents
  • fast Na blockers
  • divided into 1a,1b and 1c
26
Q

What is the most important class 1 drug?

A

flecainide (1c)

27
Q

What do Class 1a drugs do?

A
  • block sodium channels
  • delay repolarisation
  • increase AP duration
  • moderate na channel blockage
28
Q

What are Class 1a drugs used to treat? (5)

A
  1. atrial fibrillation
  2. premature atrial contractions
  3. premature ventricular contraction
  4. ventricular tachycardia
  5. Wolff-Parkinson- White Syndrome
29
Q

What do Class 1b drugs do?

A
  • block sodium channels
  • accelerate repolarisation
  • decrease AP duration
  • weak na channal blockade
30
Q

What are Class 1b drugs used to treat? (3)

A
  1. ventricular dysrhythmias only (premature ventricular contractions, ventricular tachycardia, ventricular fibrillation) ie anything to do with ventricles
31
Q

What do Class 1c drugs do?

A
  • block sodium channels (more pronounced effect)
  • little effect on AP duration or repolarisation
  • strong na channel blockade
32
Q

What are class 1c drugs used for? (3)

A
  • for severe ventricular dysrhytmias
  • for atrial fibrillation
  • for atrial flutter
33
Q

What do class 2 drugs do?

A
  • reduce or block sympathetic nervous system stimulation thus reducing transmission of impulses in the heart’s conduction system (block adrenaline receptor: adrenergic receptors)
  • depresses phase 4 depolarisation
34
Q

What are class 2 drugs used to treat? (3)

A
  1. depressant for supraventricular and ventricular arrhythmias
  2. atrial fibrillation (esp. Bisoprolol)
35
Q

What do class 3 drugs do?

A
  • increase AP duration
  • prolong repolarisation in phase 3
  • slow the rate at which K leaves the cell (K channel blockade)
36
Q

What are class 3 drugs used to treat? (4)

A
  1. dysrhythmias that are difficult to treat
  2. life threatening ventricular tachycardia or fibrillation
  3. atrial fibrillation or flutter
  4. sustained ventricular tachycardia
    If all of the above are resistant
    to other drugs
37
Q

What do class 4 drugs do?

A
  • block Ca channels

- depress phase 4 depolarisation

38
Q

What are class 4 drugs used to treat? (2)

A
  1. paroxysmal supraventricular tachycardia

2. rate control of atrial fibrillation and flutter

39
Q

With which drugs should class 4 drugs NOT be mixed with?

A

beta blockers

40
Q

What are another important anidysrhythmic drugs? (2)

A
  • Digoxin
  • Adenosine
    (have properties of several classes and are not placed into one particular class)
41
Q

What does digoxin do?

A
  • cardiac glycoside
  • inhibits the sodium-potassium ATPase pump
  • allows more Ca to be available for contraction and prolongs APs (creating a longer contraction)
  • Positive inotrope; improves the strength of cardiac contraction
42
Q

What is digoxin used for? (2)

A
  1. heart failure

2. atrial dysrhythmias (atrial fibrillation)

43
Q

What should be monitored in patients on digoxin? (2)

A
  1. K levels

2. drug levels (for toxicity)

44
Q

What is digoxin often used in elderly for?

A

for rate control

45
Q

What is the disadvantage to digoxin?

A
  • has a long half life (36-48 hours) which increases renal impairment
  • elderly already often have a reduced glomerular filtration rate and excretion is proportional to GFR
  • not effectively removed by dialysis
46
Q

What are signs of digoxin toxicity? (5)

A
  1. nausea and vomiting
  2. xanthopsia (yellow vision)
  3. bradycardia
  4. tachycardia
  5. arrhythmias; ventricular tachycardia and ventricular fibrillation
47
Q

What is the treatment for digoxin toxicity? (2)

A
  1. stop digoxin (but remember long half life)

2. if levels very high and risk of big arrhythmia then give Digibind

48
Q

What is digibind and what does it do?

A
  • it’s a Digoxin immune antibody
  • binds with digoxin forming complex molecules
  • it’s excreted in the urine
49
Q

In what circumstances is digoxin toxicity more serious?

A

More serious if K levels are low

2. Cardiovascular System (42 decks)

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