What are the mechanisms of tachycardias

• Re-entry
• Enhanced automaticity (triggered activity)

What is a Vaughan Williams' class 1A drug?

Examples?

Na Channel blocker - prolongs action potential

quinidine, procainamide, disopyramide

What main type of arrhythmias are Class 1A sodium channel blockers used for.

What are side effects/adverse effects of procainamide?

hypersensitivity (fever and skin rashes)

blood dyscrasias

sypmtoms similar to SLE

• fatigue
• loss of appetite
• nausea

What main type of arrhythmias are Class 1B sodium channel blockers used for?

what are examples of class 1B sodium channel blockers?

lignocaine (lidocaine)

mexiletine

what main type of arrhythmia is lignocaine (lidocaine) used for

what are the possible side effects of lignocaine?

CNS disturbances:

drowsiness, headaches, dizziness, convulsions

Vaughan Williams' Class 1C drugs inlcude

propafenone (not on PBS)

flecainide

What are Class 1C drugs used for?

Both SVT and VT

- Afib, proxysmal SVT, or VT

What effect does Class 1C drugs have on action potential?

None

What action does flecainide have on the heart

marked depression of cardiac contractility

proarrhythmic

What action does propafenone have on the heart?

marked depression of cardiac contractility

proarrhythmic

What type of arrhythmias are flecainide used for?

Both SVT and VT

What are Vaughan William Class II drugs?

Beta-blockers

 - propranolol, metoprolol, atenolol, alprenolol, and pindolol

 - esmolol > beta1-selective

In arrhythmias, what are beta-blockers used for?

1. Rapid ventricular rate control during Afib or atrial flutter.

2. Preventing VT induced by incresed sympatheic activity                        (during acute MI)

What is a Vaughan Willliams Class III drug?

K+ channel blocker

sotalol, amiodarone

What action does beta-blockers have in arrhythmias?

Reduciton in automaticity in SA node and in conduction velocity through AV node

In arrhythmias, what is esmolol used for?

Ventricular rate control in patients with Afib

What side effect develops in 20% of patients who have been given esmolol?

hypotension

What is sotalol's action

prolong the duration of action potentional and Effective refactory period (ERP)

What Vaughan Williams class is amiodarone?

Class III - K+ channel blocker

What action does amiodarone have?

prolongs the duration of aciton potential and ERP

What  is amiodarone used for?

treat and prevent SVT (including Afib) and VT

What are adverse effects and drug interactions of amiodarone?

proarrhythmic rare

photosensitive skin rashes

thyroid abnormalities (hyper- or hypo-)

pulmonary fibrosis

corneal deposits

increase Cp of digoxin

increase actions of warfarin

What is the drug regimen for amiodarone?

Need loading dose

eg. 200 tid X 1 week

      200 bd X 1 week

      200 1d .......

What is a Vaughan Williams Class IV drug

Calcium Channel Blockers - verapamil

What are the mechanisms of CCBs?

• shortens plateau phase of action potential
• inhibits the transient inward current and suppresses premature extopic beats/premature contraction
• slowing AV node conduction velocity

In arrhythmias, what is the clinical use of verapamil

suprpress the conduction of AVN > terminate SVT

What are the side effects of verapamil?

negative inotropic effect (strength of contraction) and heart failure

bradycardia or AV conduction block

*** Verapamil should never be used with Beta-blockers

*** Verapamil increases serum levels of digoxin

What are some Vaughan Williams' Class V drugs

digoxin

adenosine - stops conduction of AV node for 10-15 seconds

atropine

bretylium

What is the treatment for Sinus tachycardia?

treat the cause: thyrotoxicosis, anxiety, heart failure, etc.

if there is no underlying cause

 - generally no need for drug therapy, OR

 - atenolol, OR

 - metoprolol

What is the management of Paraoxysmal Supraventricular Tachycardia (PSVT)?

Non-drug therapy - radiofrequency catheter ablation (RFCA)

Conversion to sinus rhythm

 - adenosine iv

 - verapamil iv

Prophylaxis (chronic management)

 - atenolol, OR metoprolol, OR, sotalol, OR, flecainide, OR, verapamil SR, OR, amiodarone

What are the therapeutic goals of Afib treatment?

Prevention of stroke - anticoagulants - warfarin/aspirin

Prevention of ventricular dysfunction

 - control of heart rate during Afib (rate control)

 - maintenance of sinus rhythm (rhythm control)

What drugs are used for rate control in Afib?

• sotalol
• flecainide
• amiodarone

What drugs are used for ventricular control (maintanence) in Afib?

• digoxin
• diltiazem controlled-release, OR verapamil sustained-release
• atenolol OR metoprolol

What drugs are often used to reduce symptoms of premature ventricular contractions

metoprolol or atenolol

What drug(s) is used to terminate VT of sustained VT?

lignocaine

sotalol OR amiodarone