Antiarrhythmics are medications used in the treatment or prevention of cardiac arrhythmias.
The cardiac rhythm is controlled by a natural pacemaker within the right atrium of the heart, the sinoatrial node. This node sends out electrical impulses that trigger contractions of the heart muscle. These impulses travel from the sinoatrial (SA) node, through the atrioventricular (AV) node, to the Purkinje fibers which run through the ventricular muscle. The impulse traveling from the SA to the AV node first triggers contraction of the atria, forcing blood from the atria into the ventricles. The AV node acts as a gatekeeper, delaying the impulse to maximize cardiac output. The impulse then travels through the AV node and along the Purkinje fibers, triggering contraction of the ventricles starting at the apex and traveling towards the base. After the impulse passes through the heart, there is a time period called the refractory period when the heart is unable to contract again.
Disturbances such as dead cardiac tissue from heart attacks, congenital problems or medications (among other things) can cause problems with this electrical system, known as arrhythmias.
Antiarrhythmics
Brand/Generic Drug Names
moricizine, procainamide, quinidine, lidocaine, mexiletine, phenytoin, propafenone, acebutolol, propranolol, amiodarone, bretylium, verapamil, adenosine, atropine, digoxin
Common uses
premature ventricular contractions, tachycardia, hypertension, atrial fibrillation, angina pectoris
Pharmacology
Class I: increase duration of action potential and refractory period, normalize refractory period
Class II: decrease rate of SA node discharge, increase recovery time, slow AV conduction, decrease heart rate decreasing myocardial oxygen consumption
Class III: increase duration of action potential and refractory period
Class IV: inhibit calcium ion influx across cell membrane during cardiac depolarization, decrease SA node discharge, decrease AV conduction velocity
Adenosine: slows AV conduction
Digoxin: decreases conduction velocity, prolongs refractory period in AV node
Class contraindications
varies by drug
Class precautions
varies by drug
Interactions
Adverse Reactions
varies by drug
Additional Information
Assess ECG continuously to assess dysrhythmias
Assess blood pressure continuously for hypotension, hypertension
Assess for dehydration or hypovolemia, edema, intake and output
Evaluate therapeutic response: decreased blood pressure, edema, moist rales
Date of most recent Update
August 07, 2002
Further information is available in the writeup for the
specific name(s) of this medication class