CLASS
DRUG
+
Na channel blockers
- Procainamide
- Disopyramide
+
Na channel blockers
- Lignocaine
- Lidocaine
IC
+
Na channel blockers
- Propafenone
- Flecainide
II
INDICATION
+
I/IA
IB
ACTION
b-blockers
- atenolol
- propranolol
- sotalol*
III
Blocks open Na channels à prevents
depolarization à lengthens refractory period
- inotrope
•
•
•
•
•
+
Blocks inactivated Na channels (inactivated
by anoxia in ischaemic area) [selective
binding to ischaemic tissue]
Dissociate slowly from activated Na
channels
+
•
•
•
•
•
•
•
Block action of NA and Ad on adrenergic
receptors :. blocks conduction through AV
node and slows conduction through SA node.
+
+
Blocks repolarization by blocking K , Na ,
2+
Ca and b-receptors à prolong action
potential and refractory period (prolongs QT)
+
ADVERSE EFFECTS
Supraventricular + ventricular arrhythmia
Maintenance Tx
procainamide has ↓ anti-muscarinic action à
indicated as prophylaxis after MI to prevent
ventricular arrhythmia.
Prevents ectopic beats.
WPW
Ventricular-selective
After acute MI to prevent arrhythmia.
Local anaesthetic
Lidocaine – least cardiotoxic of all drugs
Suppresses ectopic beats.
Used for arrhythmias and maintenance of sinus
rhythm.
C/I in structural and ischaemic heart disease
nd
•
•
•
•
•
•
•
Supraventricular tachycardia (2 line)
Reverses remodelling of heart
Anti-ischaemic effects
C/I if PR > 0.24s
Supraventricular + ventricular arrhythmia
effective when other drugs have failed
Maintenance of sinus rhythm
•
•
Supraventricular tachyarrhythmia (3 line)
(Hypertension, angina)
K channel blockers
- amiodorone (15s doa)
- sotalol* (t1/2 = 150d)
2+
IV
2+
Ca channel blockers
- verapamil
- diltiazem
Blocks entry of Ca into myocardium à ↓
rate of depolarisation by blocking conduction
through AV node and slowing conduction
through SA node.
rd
* Sotalol is class II and III à Lacks adverse effects of amiodorone, and has same side-effects as b-blockers.
Digoxin and adenosine are also considered anti-arrhythmic therapy.
st
Adenosine ↑ outward K+ current à hyperpolarizion. C/I: asthma D/I: caffeine, theophylline. Indication: 1 line for supraventricular tachyarrhythmia.
•
•
•
•
•
•
•
•
•
•
•
•
↑ toxicity (reversible SLE-like syndrome)
hypotension
aggravation of HF
GIT (nausea, vomiting)
Anticholinergic effects (limits use in men à urinary
retention).
Cinchonism
Torsades de Pointe
Ventricular asystole (cannot be corrected by
defibrillation) :. last resort.
Seizures
•
Constipation/diarrhoea/ nausea/ vomiting
Dyspnoea
Cardiac rate disturbance (supraventricular and
ventricular arrhythmias)
AV block
•
•
•
Bradycardia
Worsens COPD + diabetes
Heart block
•
•
•
•
•
•
•
•
•
•
•
•
AV/SA nodal block
Photosensitivity
Thyroid dysfunction (↑ [iodine])
Neuropathy
Pulmonary alveolitis/fibrosis
↓ cardiotoxicity
Torsades de Pointe
Hepatotoxicity
Corneal deposits
AV/SA nodal problems (AV nodal block, bradycardia).
Headache
Ankle oedema due to vasodilation (i.e. not true
oedema).
Gingival hyperplasia
Constipation
Hyperprolactinaemia
Hyperglycaemia
•
•
•
•
ABC of SVT Mx:
Adenosine
b-blocker
2+
Ca channel blocker
MEGAN DAVIDSON