Please enable JavaScript.
Coggle requires JavaScript to display documents.
Arrhythmia Treatment (Classified Anti-arrhythmics) (Class II - Beta…
Arrhythmia Treatment
(Classified Anti-arrhythmics)
Class I - Use-dependant Na+ Channel Blockers
Mechanism of action:
Selectively blocks rapidly firing cells (more frequent access to open & inactivated Na+ channels) eg. ectopic beats, premature beats
Selective blocks partially depolarised cells (with many inactivated Na+ channels) eg. ischaemia
Drugs:
Class 1a (Dysopyramide) has an intermediate dissociation rate
Class 1b (Lignocaine) dissociates very rapidly
Class 1c (Flecainide) dissociates very slowly
Clinical effects:
Decreased rate of depolarisation
Decreased AV conduction
Decreased contractility
Clinical use:
Dysopyramide oral - Ventricular arrhythmias refractory to other treatment
Lignocaine IV - Ventricular arrhythmias
Flecainide oral or IV - Atrial or ventricular arrhythmias refractory to other treatment
Adverse effects:
Hypotension
Arrhythmias (longer dissociation rate --> more pro-arrhythmic)
Drowsiness, dizziness, confusion, visual disturbances, tinnitus
Class II - Beta-blockers
Mechanism of action:
Blocks beta-1 receptors on cardiac muscle
This opposes SNS action on the heart
Drugs:
Metoprolol, atenolol
(These beta-blockers are cardio-selective)
Clinical effects:
Decreased HR
Decreased AV conduction
Decreased contractility
Adverse effects:
Bradycardia, fatigue, cold extremities, bronchoconstriction, nightmares, hypoglycaemia
Precautions:
Asthma & COPD
Bradycardia
Uncontrolled heart failure
Peripheral vascular disease
Diabetes
Clinical use:
Tachyarrhythmias (especially stress induced)
Class III - K+ Channel Blockers
Amiodarone
Mechanism of action:
Blocks K+ channels
Also has some class I, II & IV actions
Clinical effects:
Decreased HR
Clinical use:
Ventricular & atrial arrhythmias
Commonly used to revert back to sinus rhythm
Pharmacokinetics:
Extensively bound to tissues resulting in half-life from 10-100 days
Inhibits hepatic enzymes resulting in many drug interactions
Adverse effects:
Hyper/hypothyroidism, pulmonary fibrosis (requires monitoring), skin abnormalities, GI disturbances, corneal deposits, peripheral neuropathy, liver damage, torsades de pointes
Sotalol
Mechanism of action:
Blocks K+ channels
Also has some non-selective beta-blocker action
Clinical effects:
Decreased HR
Decreased contractility
Clinical use:
Ventricular & atrial arrhythmias
Commonly used to revert back to sinus rhythm
Adverse effects:
Beta-blocker adverse effects
Arrhythmias including Torsades de pointes
Class IV - Cardio-selective Ca2+ Channel Blockers
Drugs:
Verapamil, Diltiazem
Mechanism of action:
Blocks Ca2+ channels
Verapamil is relatively selective for cardiac muscle Ca2+ channels
Diltiazem blocks Ca2+ channels in cardiac muscle & vascular smooth muscle (less cardiac effects than verapamil)
Clinical effects:
Decreased HR
Decreased AV conduction
Decreased contractility
Clinical use:
Atrial tachyarrhythmias
Adverse effects:
Bradycardia, AV block
Headache, flushing, peripheral oedema (diltiazem only), constipation (verapamil only)