Antiarrhythmic agent
Antiarrhythmic drug is a generic term for drugs which are used to treat heart rhythm disorders. Traditional antiarrhythmic drugs are classified according to their electrophysiological mechanisms of action into four classes (I to IV according to Vaughan Williams). The utility of this classification has often been questioned because some antiarrhythmic agents have properties of several classes. For example, in addition to sotalol blocked potassium channels and beta receptors. Amiodarone and dronedarone have effective properties of all classes. There are also antiarrhythmic drugs can be classified into any of the classes. It is noteworthy that each antiarrhythmic has a proarrhythmic potential, ie Can trigger cardiac arrhythmias. In particular, the combination of several antiarrhythmic drugs can thus be problematic.
Classification of antiarrhythmic drugs
The common classification was developed by E. M. Vaughan Williams proposed.
Class I - Sodium channel blockers
Class I antiarrhythmic agents binding to a voltage-dependent sodium channel, which is responsible for depolarization of the action potential. Depending on the affinity and dissociation rate of the channel is further divided into three subclasses instead. After an increased mortality was detected compared to placebo in the CAST study published in 1991, class I antiarrhythmics are, with the exception of ajmaline, flecainide and propafenone used today as good as no longer.
Causing a slowing of the depolarization by blocking the sodium channels as well as a prolongation of repolarization by blocking potassium channels and thus lead to a prolongation of the action potential. Agents: quinidine, procainamide, disopyramide, ajmaline, Prajmalin and ajmalicine.
Causing a shortening of the action potential. Active ingredients: lidocaine, mexiletine, phenytoin, and tocainide.
Cause a marked slowing of the depolarization without effect on the action potential duration. Active ingredients: flecainide, propafenone, and aprindine Moricizin ..
Class II - Beta blockers
Beta-blockers reduce over the blockade of β1 - adrenergic receptors on cardiac muscle, the sinus rate (negative chronotropic ), slow AV conduction (negative dromotropic ) and decrease myocardial excitability (negative bathmotrop ). Active ingredients: metoprolol, bisoprolol, nebivolol and much more
Class III - Potassium channel blockers
By blocking potassium channels, repolarization is slowed down and thus prolongs the action potential. Agents: amiodarone, bretylium, dofetilide, dronedarone, ibutilide, sotalol, vernakalant
Class IV - Calcium channel blockers
Calcium channel blockers from Phenylalkylamintyp or Benzothiazepintyp reduce over blockade of calcium channels, L-type heart rate and delay AV conduction. Active ingredients: verapamil, diltiazem, gallopamil and flunarizine.
Other antiarrhythmic drugs
Adenosine
Adenosine leads to binding at A1 adenosine receptors via activation of Gi- modulated potassium channel in the short term, a few seconds ongoing blockade of the AV conduction. The medication is used for the diagnosis and acute therapy of cardiac arrhythmias, at the causation of the AV node is involved.
Digitalis
Digitalis lead via the inhibition of myocardial sodium - potassium ATPase to a positive inotropic and negative dromotropic effect and to thereby reduce the heart rate. It is used for braking quickly übergeleitetem atrial fibrillation. Active ingredients: digoxin, digitoxin
Parasympatholytics
Parasympatholytics prevented by the blockade of muscarinic M2 and M4 receptors, the opening of K channels t (positive chronotropic and dromotropic effect). Agents: atropine, ipratropium bromide
Sympathomimetic
Agonists act through the activation of myocardial beta1- adrenoceptor positive chronotropic, dromotropic and bathmotrop. Active ingredients: adrenaline, noradrenaline, and much more orciprenaline
If- channel blockers
As the only representative of this group ivabradine lowers heart rate isolated on sinus node through the specific inhibition of the If channel.