Practically all patients of the cardiologist faced one way or another with various kinds of arrhythmias. Currently, the pharmacological industry offers a wide variety of antiarrhythmic drugs. Their classification and characteristics will be considered in this article.
Routes of influence
Antiarrhythmic drugs are prescribed to eliminate ectopic heart rhythm disturbances. The mechanism of action of such drugs is aimed at the electrophysiological properties of working myocardial cells:
- Reducing the speed of the action potential, which helps to slow down the conduction of excitation.
- Reduce myocardial excitability.
- Shortening the relative refractoriness time, which shortens the interval when an extraordinary impulse can trigger a heartbeat.
- Prolonging the period of effective refractoriness, which is important for tachycardias and to eliminate impulses that occur too short an interval after the optimal contraction.
- Increasing the speed of excitation, which contributes tohomogenization and prevents the re-entry phenomenon (“re-entry”).
- Inhibition of the focus of ectopic automatism, which is associated with a prolongation of the period of diastolic depolarization.
- Eliminating differences in conduction velocity and refractoriness.
- Decreased cardiac sensitivity to electrical shock and risk of ventricular fibrillation.
Classification of antiarrhythmic drugs
All drugs in this group are divided into four classes. Additionally, the first class is divided into three more subclasses. This classification is based on the degree to which drugs affect the ability of heart cells to generate and conduct electrical signals. Different classes of antiarrhythmic drugs have different routes of action, so their effectiveness will differ for different types of arrhythmia.
The first class includes blockers of fast sodium channels. Subclass IA includes drugs such as Quinidine, Disopyramide, Novocainamide, Gilurithmal. Subclass IB includes Pyromecaine, Tocainide, Difenin, Lidocaine, Aprindine, Trimecaine, Mexiletine. The IC subclass is formed by such agents as Etmozin, Ritmonorm (Propafenone), Allapinin, Etatsizin, Flecainide, Indecainide, Bonnecor, Lorcainide.
The second class consists of beta-blockers (Metoprolol, Nadolol, Alprenolol, Kordanum, Propranolol, Acebutalol, Pindolol, Trazikor, Esmolol).
The third class includes potassium channel blockers:Bretylium Tosylate, Amiodarone, Sotalol.
The fourth class includes blockers of slow calcium channels (for example, "Verapamil").
The list of antiarrhythmic drugs does not end there. Cardiac glycosides, potassium chloride, sodium adenosine triphosphate, magnesium sulfate are also isolated.
First class drugs
Blockers of fast sodium channels stop the flow of sodium into the cells, which slows down the passage of the excitation wave through the myocardium. Thanks to this, the conditions for rapid circulation of pathological signals in the heart are stopped, and the arrhythmia is eliminated. Let us consider in more detail the groups of antiarrhythmic drugs belonging to the first class.
IA class medicines
Such antiarrhythmic drugs are prescribed for extrasystoles (ventricular and supraventricular), as well as to restore sinus rhythm in case of atrial fibrillation (atrial fibrillation). In addition, they are used to prevent recurrent attacks.
"Novocainamide" and "Quinidine" are effective antiarrhythmic drugs for tachycardia. Let's talk about them in more detail.
Quinidine
This medication is used in cases of paroxysmal supraventricular tachycardia, as well as paroxysms of atrial fibrillation, to restore sinus rhythm. Most often, the medicine is prescribed in the form of tablets.
Poisoning with antiarrhythmic drugs is rare, but when taking Quinidine, side effects in the form of a disorder are possibledigestion (vomiting, loose stools) and headache. In addition, the use of this medication can cause a decrease in the level of platelets in the blood, a slowdown in intracardiac conduction, and a decrease in myocardial contractility. The most dangerous side effect is the development of a special form of ventricular tachycardia, which can cause sudden death of the patient. That is why Quinidine therapy should be carried out only with the control of the electrocardiogram and under the supervision of a specialist.
The drug is contraindicated in intraventricular and atrioventricular blockade, intoxication with cardiac glycosides, thrombocytopenia, arterial hypotension, heart failure, pregnancy.
Novocainamide
This medication has the same indications for use as Quinidine. Quite often it is prescribed for the purpose of stopping paroxysms of atrial fibrillation. With an intravenous injection of Novocainamide, a sharp decrease in blood pressure is possible, as a result, it is necessary to administer the solution as slowly as possible.
Among the side effects are nausea, vomiting, changes in the composition of the blood, disorders of the nervous system in the form of dizziness, headache, in rare cases, confusion. If you use the drug constantly, a lupus-like syndrome (serositis, arthritis, fever), a microbial infection in the oral cavity, accompanied by slow healing of wounds and ulcers and bleeding gums, may develop. In addition, Novocainamide can provoke an allergicreaction, in this case the first sign will be the appearance of muscle weakness when the drug is administered.
It is prohibited to use the medication for atrioventricular blockade, severe forms of renal and heart failure, arterial hypotension and cardiogenic shock.
IB class
These drugs have little effect on the sinus node, the atrioventricular junction, and the atria, and are therefore ineffective in the case of supraventricular arrhythmia. These antiarrhythmic drugs are prescribed for extrasystole, paroxysmal tachycardia, that is, for the treatment of ventricular arrhythmias. They are also used to treat arrhythmias that are triggered by an overdose of cardiac glycosides.
The list of antiarrhythmic drugs of this class is quite extensive, but the most commonly used remedy is Lidocaine. As a rule, it is administered intravenously in case of severe ventricular arrhythmias, including myocardial infarction.
"Lidocaine" can disrupt the functioning of the nervous system, which is manifested by dizziness, convulsions, problems with speech and vision, impaired consciousness. If you enter the drug in a large dose, it is possible to slow down the heart rate, reduce the contractility of the heart. In addition, allergic reactions are likely in the form of Quincke's edema, urticaria, skin itching.
"Lidocaine" is contraindicated in atrioventricular blockade, sick sinus syndrome. The drug is not prescribed in case of severe supraventricular arrhythmia, as the risk of atrial fibrillation increases.
IC class
Drugs belonging to this class lengthen intracardiac conduction, especially in the His-Purkinje system. They have pronounced arrhythmogenic properties, so their use is currently limited.
The list of antiarrhythmic drugs of this class was given above, but of these, only Propafenone (Ritmonorm) is mainly used. It is prescribed for supraventricular and ventricular arrhythmias, including with ERW syndrome. Since there is a risk of an arrhythmogenic effect, the drug should be used under the supervision of a doctor.
In addition to arrhythmias, this drug can cause progression of heart failure and deterioration of heart contractility. Side effects include a metallic taste in the mouth, nausea, and vomiting. Negative effects such as visual disturbances, changes in blood tests, dizziness, insomnia, depression are not excluded.
Beta-blockers
When the tone of the sympathetic nervous system increases, for example, in case of stress, hypertension, vegetative disorder, ischemia, a lot of catecholamines appear in the blood, including adrenaline. These substances act on myocardial beta-adrenergic receptors, which leads to electrical cardiac instability and the appearance of arrhythmias.
Beta-blockers prevent excessive stimulation of receptors and thus protect the myocardium. In addition, they reduce the excitability of the cells of the conduction system, which leads toslow heart rate.
Medicines of this class are used in the treatment of atrial flutter and fibrillation, for the prevention and relief of supraventricular arrhythmia. In addition, they help to overcome sinus tachycardia.
Ineffective considered antiarrhythmic drugs for atrial fibrillation, except in cases where the pathology is caused precisely by an excess of catecholamine in the blood.
Metoprolol and Anaprilin are often used for the treatment of rhythm disturbances. These drugs have side effects in the form of a slowing of the pulse, a decrease in myocardial contractility, and the occurrence of atrioventricular blockade. These medications can provoke cold extremities and deterioration of peripheral blood flow. In addition, drugs affect the nervous system, causing drowsiness, dizziness, depression, and memory impairment. They also change the conduction in nerves and muscles, resulting in fatigue and weakness.
Beta-blockers are prohibited for use in cardiogenic shock, pulmonary edema, insulin-dependent diabetes mellitus, bronchial asthma. Also contraindications are atrioventricular blockade of the second degree, sinus bradycardia.
Potassium channel blockers
The list of antiarrhythmic drugs of this group includes drugs that slow down electrical processes in the cells of the heart and thereby block potassium channels. The most famous drug of this class is Amiodarone (Cordarone). Among other things, itacts on M-cholinergic and adrenergic receptors.
"Kordaron" is used for the treatment and prevention of ventricular, atrial and supraventricular arrhythmia, heart rhythm disturbances against the background of ERW syndrome. The drug is also prescribed to prevent life-threatening ventricular arrhythmia in patients with acute heart attack. In addition, it is used to reduce the heart rate in persistent atrial fibrillation.
If you use the product for a long time, interstitial pulmonary fibrosis may develop, skin color may change (the appearance of a purple tint). In some cases, there are headaches, sleep disturbances, memory, vision. Taking Amiodarone may cause sinus bradycardia, constipation, nausea and vomiting.
Do not prescribe medication for initial bradycardia, prolongation of the Q-T interval, impaired intracardiac conduction, thyroid diseases, arterial hypotension, pregnancy, bronchial asthma.
Slow calcium channel blockers
These drugs block the slow flow of calcium, thereby suppressing ectopic foci in the atria and reducing the automatism of the sinus node. The list of antiarrhythmic drugs in this group includes "Verapamil", which is prescribed for the prevention and relief of paroxysms of supraventricular tachycardia, for the treatment of supraventricular extrasystole. Verapamil is not effective for ventricular arrhythmias.
Side effects includeatrioventricular blockade, sinus bradycardia, arterial hypotension, and in some cases - a decrease in cardiac contractility.
Cardiac glycosides
Classification of antiarrhythmic drugs would not be complete without mentioning these drugs. These include drugs such as Celanide, Korglikon, Digitoxin, Digoxin, etc. They are used to restore sinus rhythm, stop supraventricular tachycardia, and reduce the frequency of ventricular contractions in case of atrial fibrillation. When using cardiac glycosides, you need to monitor your condition. Signs of digitalis toxicity include abdominal pain, nausea and vomiting, headaches, visual and sleep disturbances, and nosebleeds.
It is forbidden to use these antiarrhythmic drugs for bradycardia, SVC syndrome, intracardiac blockades. They are not prescribed in case of paroxysmal ventricular tachycardia.
Combination of antiarrhythmic drugs
With ectopic rhythms, some combinations of drugs are used in clinical practice. So, "Quinidine" can be used in conjunction with cardiac glycosides for the treatment of persistent extrasystole. With beta-blockers, Quinidine can be prescribed to stop ventricular arrhythmias that are not amenable to other treatment. The combined use of beta-blockers and cardiac glycosides gives a good effect on ventricular and supraventricular extrasystoles, and also helps prevent recurrence of tachyarrhythmias and ectopic tachycardias.
