Antiarrhythmic
Antiarrhythmic is a generic term for drugs that can be used to treat cardiac arrhythmias . Traditionally, antiarrhythmics are divided into four classes (I to IV according to Vaughan Williams) according to their electrophysiological mechanisms of action. The usefulness of this classification has been questioned many times because some antiarrhythmic drugs have properties of several classes. For example, in addition to potassium channels, sotalol also blocks beta receptors. Amiodarone and dronedarone have properties of all classes. There are also antiarrhythmics that cannot be assigned to any of the classes. It is noteworthy that every antiarrhythmic drug also has a proarrhythmic potential, i. H. Can trigger cardiac arrhythmias. In particular, the combination of several antiarrhythmics can therefore be problematic.
Classification of antiarrhythmics
The common classification was suggested by EM Vaughan Williams.
Class I - sodium channel blockers
Class I antiarrhythmics bind to a voltage-dependent sodium channel, which is responsible for the depolarization of the action potential . Depending on the affinity and dissociation speed to the channel, there is a further subdivision into three subclasses. After the CAST study published in 1991 showed an increased mortality compared to placebo, class I antiarrhythmics are almost no longer used with the exception of ajmaline , flecainide and propafenone .
Class IA (quinidine-like)
Class IA antiarrhythmics slow down the rate of depolarization by blocking the sodium channels and lengthen the repolarization time by blocking potassium channels, thus lengthening the action potential (see also QT syndrome ).
Active ingredients: quinidine , procainamide , disopyramide , ajmaline , prajmaline and ajmalicin .
Class IB (lidocaine-like)
Cause a shortening of the action potential.
Active ingredients: lidocaine , mexiletine , phenytoin and tocainide .
Class IC (mixed type)
They cause a pronounced slowing down of the rate of depolarization without any effect on the duration of the action potential.
Active ingredients: flecainide , propafenone , aprindine and moricizine .
Class II - beta blockers
Beta blockers reduce the sinus frequency (negative chronotropic ) by blocking the β 1 -adrenoceptors on the heart muscle , slow down the AV conduction (negative dromotropic ) and reduce myocardial excitability (negative bathmotropic ).
Active ingredients: propranolol , metoprolol , atenolol , bisoprolol , nebivolol and many more
Class III - potassium channel blockers
By blocking potassium channels, the repolarization is slowed down and the action potential is lengthened.
Active ingredients: Amiodarone , Bretylium , Dofetilid , Dronedaron , Ibutilid , Sotalol , Vernakalant
Class IV - calcium channel blockers
Calcium channel blockers of the phenylalkylamine or benzothiazepine type lower the heart rate by blocking calcium channels of the L-type and delay the AV conduction.
Active ingredients: verapamil , diltiazem , gallopamil , flunarizine and diprafenone .
Other antiarrhythmics
Adenosine
Adenosine leads to binding to the A 1 - adenosine receptors , activation of a G i -modulated potassium channel in the short term, a few seconds lasting blockade of the AV conduction . The drug is used for the diagnosis and acute therapy of cardiac arrhythmias, which the AV node is involved in causing.
Digitalis glycosides
By inhibiting the myocardial sodium-potassium-ATPase, digitalis glycosides lead to a positive inotropic and also to a negative dromotropic effect and thus reduce the heart rate. It is used to slow down rapidly transferred atrial fibrillation.
Active ingredients: digoxin , digitoxin
Parasympatholytics
Parasympatholytics prevent the opening of potassium channels by blocking muscarinic M 2 and M 4 receptors (positive chronotropic and dromotropic effect).
Active ingredients: atropine , ipratropium bromide
Sympathomimetics
Sympathomimetics have a positive chronotropic, dromotropic and bathmotropic effect by activating myocardial beta 1 -adrenoceptors .
Active ingredients: adrenaline , noradrenaline , orciprenaline and many more
I f channel blocker
Ivabradine is the only representative of this group to lower the heart rate in isolation at the sinus node via the specific inhibition of the I f channel .
magnesium
Magnesium is a natural component of the body; a lack of magnesium can lead to cardiac arrhythmias. However, regardless of a deficiency situation, magnesium administration can treat certain arrhythmias. It is the drug of choice for torsade de pointes tachycardias and is also indicated for digitalis- induced cardiac arrhythmias and multifocal atrial tachycardias. For optimal bioavailability, organically bound magnesium, such as. B. Magnesium citrate or trimagnesium dicitrate recommended as powder or powder capsules in pure form.
literature
- Reinhard Larsen: Anesthesia and intensive medicine in cardiac, thoracic and vascular surgery. (1st edition 1986) 5th edition. Springer, Berlin / Heidelberg / New York et al. 1999, ISBN 3-540-65024-5 , pp. 71-77.
Web links
Individual evidence
- ^ A b Vaughan Williams EM. "Classification of anti-arrhythmic drugs." In: Symposium on Cardiac Arrhythmias , Sandfte E, Flensted-Jensen E, Olesen KH eds. Sweden, AB ASTRA, Södertälje, 1970; 449-472.
- ↑ Real DS, Liebson PR, Mitchell LB, et al. : Mortality and morbidity in patients receiving encainide, flecainide, or placebo. The Cardiac Arrhythmia Suppression Trial . In: N. Engl. J. Med. . 324, No. 12, March 1991, pp. 781-8. PMID 1900101 .
- ↑ Aktories, U. Förstermann, FB Hofmann, K. Starke: Repetitorium General and Special Pharmacology and Toxicology. 2nd edition, p. 163.
- ^ Lewalter, Lüderitz: Cardiac arrhythmias - Diagnostics and Therapy, 6th edition, 2010.
- ↑ Lindberg, JS; Zobitz, MM; Poindexter, JR; Pak, CY: Magnesium bioavailability from magnesium citrate and magnesium oxide. Journal of the American College of Nutrition 9 (1), 1990, pp. 48-55. PMID 2407766 .
