Arrythmias: Therapy Flashcards
1
Q
What is an arrhythmia?
A
Any deviation from the normal rhythm of the heart
2
Q
What are the 4 major classes of arrhythmias?
A
- Sinus arrhythmia
- Supraventricular arrhythmia
- Ventricular arrhythmia
- Heart block
3
Q
What is responsible for the resting membrane potential?
A
- Inside the cardiac cell there is a net negative charge relative to the outside of the cell
- Due to uneven distribution of ions across the membrane
- Sodium potassium ATPase pump maintains this
4
Q
What causes cardiac cells to become excited?
A
A change in distribution of ions
5
Q
What results in the propagation of the electrical impulse?
A
Movement of ions across the cardiac cell’s membrane
6
Q
What does the electrical impulse lead to?
A
Contraction of the myocardial muscle
7
Q
What is the Vaughan-Williams classification of drugs to treat arrhythmias?
A
- Class Ia
- Class Ib
- Class Ic
- Class II
- Class III
- Class IV
- Other
8
Q
What is the electrophysiological property of class IA drugs?
A
Fast sodium-channel blockade
9
Q
What is the electrophysiological property of class IB drugs?
A
Intermediate sodium-channel blockade
10
Q
What is the electrophysiological property of class IC drugs?
A
Slow sodium-channel blockade
11
Q
What is the electrophysiological property of class II drugs?
A
B-Adrenergic receptor antagonism
12
Q
What is the electrophysiological property of class III drugs?
A
Prolong refractoriness
13
Q
What is the electrophysiological property of class IV drugs?
A
Calcium channel blockade
14
Q
Give 3 examples of class IA drugs.
A
- Quinidine
- Procainamide
- Dispyramide
15
Q
Give 4 examples of class IB drugs.
A
- Lidocaine
- Mexiletine
- Tocainide
- Phenytoin
16
Q
Give 2 examples of class IC drugs.
A
- Flecainide
- Propafenone
17
Q
Give 2 examples of class II drugs.
A
- Atenolol
- Bisoprolol
18
Q
Give 3 examples of class III drugs.
A
- Amiodarone
- Bretylium
- Sotalol
19
Q
Give 2 examples of class IV drugs.
A
- Diltiazem
- Verapamil
20
Q
What do class I drugs do?
A
Stabilise membrane
21
Q
What do class IA drugs do?
A
- Block sodium channels
- Delay repolarisation
- Increase action potential duration
22
Q
What are class IA drugs used to treat?
A
- Atrial fibrillation
- Premature atrial contractions
- Premature ventricular contractions
- VT
- Wolff-Parkinson-White syndrome
23
Q
What do class IB drugs do?
A
- Block sodium channels
- Accelerate repolarisation
- Decrease the action potential duration
24
Q
What are class IB drugs used to treat?
A
Ventricular dysrthmias only
- Premature ventricular contractions
- VT
- VF
25
What do class IC drugs do?
- Block sodium channels (more pronounced effect)
| - Little effect on action potential duration or repolarisation
26
What are class IC drugs used to treat?
- Sever ventricular dysrthmias
| - Can be used for atrial fibrillation/flutter
27
What are class II drugs otherwise known as?
B-blockers
28
What do class II drugs do?
- Reduce or block sympathetic nervous system stimulation, thus reducing transmission of impulses in the heart's conduction system
- Depress phase 4 depolarisation
- General myocardial depressants for both supraventricular and ventricular dysrhythmias
29
What is now the first line for atrial fibrillation?
Bisoprolol
30
What do class III drugs do?
- Increase action potential duration
| - Prolong repolarisation in phase 3
31
What are class III drugs used to treat?
- Dysrythmias that are difficult to treat
- Life-threatening VT or VF, atrial fibrillation/flutter resistant to other drugs
- Sustained VT
32
What do class IV drugs do?
-Depress phase 4 depolarisation
33
What are class IV drugs used to treat?
- Paroxysmal supraventricular tachycardia
| - Rate control for atrial fibrillation and flutter
34
Why do other antidysrhythmics not place in a class?
They have properties of several classes
35
What is digoxin?
Cardiac glycoside
36
What does digoxin do?
- Inhibits the sodium potassium ATPase pump
- Positive inotrope: improves the strength of cardiac contraction
- Allows more calcium to be available
37
What is digoxin used to treat?
- Heart failure
| - Atrial dysrhythmias
38
What must be monitored with digoxin?
-Potassium levels and drug levels for toxicity
39
Who is digoxin commonly used in?
The elderly
40
What is important to note with digoxin and the elderly?
- Many have renal impairment
| - Digoxin is not effectively removed by dialysis
41
What is the half life of digoxin?
36-48 hours
42
What are the signs and symptoms of digoxin toxicity?
- Reverse tick appearance of ST segment in lateral leads
- Nausea and vomiting
- Xanthopsia
- Bradycardia
- Tachycardia
- VT and VF
43
How is digoxin toxicity treated?
- Stop digoxin (long half life)
| - If levels are very high and risk of significant arrhythmia then give Digiband
44
What is Digiband?
- Digoxin immune antibody
- Binds with digoxin, forming complex molecules
- Excreted in urine
45
When is digoxin toxicity more serious?
If potassium levels are low
46
What is amiodarone used for?
- VT
| - Occasionally SVT
47
What does amiodarone interact with?
-Many other drugs but mainly digoxin
48
What are the side effects of amiodarone?
- Hypo/hyperthyroidism
- Pulmonary fibrosis
- Grey pigmentation
- Corneal deposits
- LFT abnormalities
49
What is adenosine used for?
To convert paroxysmal SVT to sinus rhythm
50
What does adenosine do?
Slows conduction through the AV node
51
What type of half life does adenosine have?
Short half life
52
How is adenosine administered?
Fast IV push
53
What can happen after adenosine is administered?
May cause asystole for a few seconds
54
What can all antiarrhythmics cause?
Arrythmias
55
What are the indications for anticoagulation?
- Atrial fibrillation
- Risk of stroke
- Peripheral emboli
- Valvular heart disease
- VTE
- DVT/PE
- Following surgery
- Immobilisation
56
Give examples of anti-coagulation drugs.
- Warfarin
- Dabigatran
- Rivaroxaban
- Apixaban
- Edoxaban
57
What is arterial thrombosis caused by?
Adherence of platelets to arterial walls
58
Describe an arterial thrombus.
- White in colour
| - Full of platelets/cells
59
What are arterial thrombi associated with?
- MI
- Stroke
- Ischaemia
60
What is venous thrombosis caused by?
Stagnant blood flow
61
Describe a venous thrombus.
- Red in colour
| - Full of fibrin particles
62
What are venous thrombi associated with?
- Congestive heart failure
- Cancer
- Surgery
63
Where does warfarin come from?
Sweet clover
64
What is warfarin used as?
Rat poison
65
What is warfarin structurally related to?
Vitamin K
66
What does warfarin do?
Inhibits production of active clotting factors
67
How is a warfarin overdose treated?
Vitamin K
68
Why do some drugs increase warfarin activity?
- Decrease synthesis of clotting factors
- Inhibit degradation
- Decrease binding to albumin
69
What drugs decrease binding to albumin?
- Aspirin
| - Sulfonamides
70
Why do some drugs promote bleeding?
- Inhibition of clotting factors
| - Inhibition of platelets
71
What drugs inhibit platelets?
Aspirin
72
What drugs inhibit clotting factors?
- Heparin
| - Antimetabolites
73
Why do some drugs decrease warfarin activity?
- Induction of metabolising enzymes (cytochrome P450)
- Promote clotting factor synthesis
- reduced absorption
74
What drugs induce cytochrome P450?
- Barbiturates
| - Phenytoin
75
What drugs promote clotting factor synthesis?
Vitamin K
76
What drugs reduce absorption?
Cholestyramine
77
What drugs inhibit degradation?
- Cimetidine
| - Disulfiram
78
What drugs decrease the synthesis of clotting factors?
-Oral antibiotics
79
What does the direct effect of warfarin depend on?
- Concentration of warfarin in the liver
| - Rate of accumulation of warfarin
80
Why does heparin have to be given first for DVT?
Warfarin has a long half life which means it has a slow onset of action
81
Describe the use of INR.
- International normalised ratio
- Actual thromplastin time divided by standard thromboplastin time
- Normal INR is1
- Therapeutic INR is normally 2.5-4
82
What are the adverse effects of warfarin?
- Bleeding
- Teratogenic (chondrodysplasia)
- Retroplacental bleeding and foetal intracerebral bleeding
83
How is warfarin therapy monitored?
- Regular INR
- Watch if therapy is altered
- Patient education
- Alcohol intake
84
What type of drugs can warfarin interact with?
- Macrolide antibiotics
- Antifungals
- Anti-epileptic drugs
85
How is bleeding risk assessed on warfarin?
-CHADS2 score
86
What is the CHADS2 score?
- Congestive heart failure
- Hypertension
- Age>75
- Diabetes mellitus
- Stroke/TIA
87
What are the characteristics of the ideal anticoagulant?
- Oral
- No need for monitoring
- No interaction with food or drugs
- Given once or twice a day/ fixed dose irrespective of body weight/age
- As effective as warfarin
- Safer than warfarin
88
Give 2 examples of direct thrombin inhibitors.
- Dabigatran
| - Apixaban
89
What is rivaroxaban?
Factor Xa inhibitor
