Anti-arrhythmic drugs overview

Question 1

what is the difference between supraventricular and ventricular arrhythmias?

Answer 1

1) Ventricular arrhythmias occur in the lower chambers of the heart: ventricles
2) Supraventricular arrhythmias occur in the area above the ventricles, usually in the upper chambers: Atria

Question 2

How are anti-arrhythmic drugs classed? (2)

Answer 2

1) Can be classified clinically into those that act on supraventricular arrhythmias, those that act on both supraventricular and ventricular arrhythmias, and those that act on ventricular arrhythmias
2) According to their effects on the electrical behavior of myocardial cells during activity (the Vaughan Williams classification) - less clinical significance

Question 3

Give an example of an antiarrhythmic drug that is used for each of the following:

1) Supraventricular arrhythmias (3)
2) Both supraventricular and ventricular (5)
3) Ventricular arrhythmias (1)

Answer 3

1) Supraventricular arrhythmias- Adenosine, Digoxin, and verapamil
2) Both supraventricular and ventricular- Amiodarone , B-blockers, disopyramide, flecainide and propafenone
3) Ventricular arrhythmias- Lidocaine

Question 4

Outline the Vaughan Williams classification for anti-arrhythmic drugs. Include examples of classes of drugs that fall in each of the four categories

Answer 4

1) Class I: membrane stabilising (e.g. lidocaine, flecainide)
2) Class II: Beta-blockers
3) Class III: amiodarone; sotalol (also Class II)
4) Class IV: CCB’s ( verapamil but not dihydropyridines)

Question 5

why should care be taken if two or more inotropic anti-arrhythmic drugs are used together?

Answer 5

The negative inotropic effects of anti-arrhythmic drugs tend to be additive

Question 6

Why can hypokalaemia be a problem in those prescribed arrhythmic drugs?

Answer 6

hypokalaemia enhances the arrhythmogenic (pro-arrhythmic) effect of many drugs

Question 7

what is the treatment of choice for paroxysmal supraventricular tachycardias and why?

Answer 7

1) Adenosine- very short duration of action so less SE. It can also be used after a B-Blocker
2) Verapamil preferable to adenosine in asthma. But cant be used after B-blocker

Question 8

Cardiac glycoside slow the ventricular response in all cases of atrial fibrillation and atrial flutter. However what type of arrhythmia are they contraindicated in?

Answer 8

Arrhythmias associated with accessory conducting pathways (e.g. Wolff- Parkinson-White syndrome

Question 9

outline the treatment options for managing supraventricular tachycardias

N.B. (Paroxysmal supraventricular tachycardias are different as they only occur from “time to time”, so short acting drug adesonine is given)

Answer 9

1) Verapamil hydrochloride- An initial IV dose, followed by oral treatment. Hypotension may occur with large doses.
↳Important: serious beta-blocker interaction hazard
2) IV beta-blocker such as esmolol or propranolol, can achieve rapid control of the ventricular rate

Question 10

when should verapimil not be used for the management of arrhythmias? (3)

Answer 10

1) When the QRS complex is wide (i.e. broad complex) unless a supraventricular origin has been established
2) Accessory conducting pathways (e.g. Wolff-Parkinson-White syndrome)
3) with B-blocker

Question 11

list the drugs that can be used for both supraventricular and ventricular arrhythmias (5)

Answer 11

1) Amiodarone
2) Beta-blockers
3) Disopyramide
4) Flecainide acetate
5) propafenone

Question 12

outline the use of amioderone in arrhythmias, including its benefits and how it should be initiated

Answer 12

1) very useful in the treatment of both supraventricular and ventricular arrhythmias. Also used for tachyarrhythmias associated with Wolff-Parkinson- White
2) Initiated only under hospital or specialist supervision.
3) advantage of causing little or no myocardial depression

Question 13

outline the pharmacological properties of amioderone stating how long it takes to reach steady state and its onset of action both orally and IV

Answer 13

1) IV amiodarone acts relatively rapidly compared to oral
2) very long half-life (extending to several weeks) given once daily (high doses can cause nausea unless divided).
3) Many weeks or months may be required to achieve steady-state plasma-amiodarone concentration; this is particularly important when drug interactions are likely.

Question 14

Beta-blockers can be used in both supraventricular and ventricular arrhythmias . How does their mode of action differ from most other antiarrhythmic agents?

Answer 14

They do not directly modifying ion channel function. They work by attenuating the effects of the sympathetic system on automaticity and conductivity within the heart

Question 15

which Beta-block can be used in the treatment of ventricular arrhythmias?

Answer 15

Sotalol

Question 16

1) when should Disopyramide be used in the management of arrhythmias?
2) who should it not be used in?

Answer 16

1) IV injection to control arrhythmias after MI
2) Oral disopyramide is useful, but it has an antimuscarinic effect which limits its use in patients susceptible to angle-closure glaucoma or with prostatic hyperplasia.

Question 17

1) when is Propafenone used in the management of arrhythmias?
2) why should it be used in caution in those with COPD?

Answer 17

1) prophylaxis and treatment of ventricular arrhythmias and also for some supraventricular arrhythmias
2) MoA involves weak beta-blocking activity

Question 18

State which drugs are used in the treatment of ventricular arrhythmias?

Answer 18

1) IV lidocaine hydrochloride can be used for the treatment of ventricular tachycardia in haemodynamically stable patients. But its NOT first line
2) Amiodarone, B-blockers, disopyramide, flecainide acetate and propafenone can also be used - these drugs are also used in supraventricular arrhythmias

Question 19

list the Rate control drugs (3)

Answer 19

1) Beta Blockers - (sotalol can be both)
2) Digoxin
3) Diltiazem and Verapamil

Question 20

list the Rhythm control drugs (4)

Answer 20

1) Flecainide
2) Amiodarone
3) Sotalol (both)
4) Propafenone
↳ more risky due to serious SE and necessity for monitoring

Question 21

sotalol is a non-selective B-Blocker, what important safety information regarding the use of this drug

Answer 21

May prolong the QT interval, and it occasionally causes life threatening ventricular arrhythmias

Question 22

what electrolyte disturbances need to be corrected before starting and during treatment with sotalol?

Answer 22

Avoid hypokalaemia in patients taking sotalol- hypokalaemia and hypomagnesaemia should be corrected before sotalol started and during use

Question 23

what are the monitoring requirements for sotalol

Answer 23

1) Measurement of corrected QT interval, and monitoring of ECG and electrolytes required
2) correct hypokalaemia, hypomagnesaemia, or other electrolyte disturbances.