Antiarrhythmics are drugs used to regulate irregular or rapid heartbeats. They are indicated for the treatment or prevention of certain cardiac arrhythmias.
Anti-arrhythmic treatment is most often initiated by a cardiologist who must first determine the nature of the arrhythmia and choose the most appropriate medication from among the many available.
Regular monitoring of the treatment is essential and can be carried out by a general practitioner.
Anti-arrhythmics: when and why are they prescribed?
An arrhythmia occurs when the heart beats less than 60 beats (bradycardia) or more than 100 beats (tachycardia) per minute without apparent cause.
Antiarrhythmic drugs are not used for all arrhythmias. They are prescribed when symptoms become severe (palpitations, malaise, onset of angina, or heart failure) or when the arrhythmia is likely to lead to serious complications. Other electromechanical (defibrillation, electric shock) or surgical methods can be used to treat certain arrhythmias.
Before initiating long-term oral treatment, the cardiologist must diagnose the exact nature of the arrhythmia and ensure that there is no underlying pathology that might contraindicate the treatment. To do this, he or she uses various tests: biological blood tests, electrocardiogram (analysis of the heartbeat), Holter-ECG (recording of the heartbeat over a 24-hour period), stress test (study of the electrocardiogram during physical effort), and cardiac ultrasound.
When treatment is deemed necessary, the cardiologist chooses the most appropriate drug for the type of arrhythmia detected, taking into account the risks of adverse effects (different for each drug), contraindications, and possible interactions with other treatments.
The main indications for antiarrhythmic drugs are:
– junctional or ventricular tachycardias (accelerated heartbeat)
– frequent and/or repetitive extrasystoles (abnormal premature contractions)
– fibrillations (anarchic activations) and flutters (very rapid but regular contractions) at the heart.
Anti-arrhythmic drugs: typology
Arrhythmias are due to a dysfunction of the electrical conduction that makes the heartbeat. This conduction depends on variations in the ionic concentrations of sodium (Na+), potassium (K+), and calcium (Ca++) on either side of the cell membrane. Antiarrhythmics vary the action potential (electrical signal) of cardiac conduction and the QT interval of the electrocardiogram, which corresponds to the duration of ventricular systole (the contraction phase).
Based on their electrophysiological properties, antiarrhythmic drugs are divided into four classes, according to the Vaughan-Williams classification:
– Class 1 antiarrhythmics decrease the rate of sodium entry and slow the propagation of the nerve impulse. They are divided into three subclasses: class 1A (quinidinics such as Longacor and Serecor or disopyramide such as Rythmodan and Isorythm); class IB such as Xylocard and class 1C such as Flecaine.
– Class 2 antiarrhythmics are beta-blockers that slow conduction at the atrioventricular node (examples: Avlocardyl, Lopressor, Tenormin, Sectral).
– Class 3 antiarrhythmics block potassium channels and lengthen repolarization, conduction velocity remains normal (examples: Cordarone, Sotalex).
– Class 4 antiarrhythmics are calcium channel blockers (e.g. Isoptin, Tarka, Tildiem), which slow down the entry of calcium into the muscle cells of the heart and slow down the transmission of nerve impulses.
Apart from this classification, other drugs such as digitalis (Digoxin) or peripheral vasodilators (Adenosine, Krenosin) can also be used to slow nodal conduction.
Precautions for using antiarrhythmic drugs
A long list of side effects and contraindications is listed in the package insert for antiarrhythmic drugs. Indeed:
– Antiarrhythmic drugs can cause many potentially serious cardiac or extracardiac side effects, sometimes limiting their use. However, these effects are rare.
– Most antiarrhythmic drugs are contraindicated in cases of severe heart failure and may interact with other treatments.
It is essential to follow the instructions for use, the dosage, and the duration of the treatment, and regular medical follow-up is necessary to monitor the tolerance and effectiveness of the medication.
As a precaution, any new cardiac or extracardiac symptom should prompt a prompt consultation of the attending physician or cardiologist.
In addition to the treatment, simple hygienic and dietary measures are recommended: avoid stimulants (coffee, tobacco, alcohol), practice a regular but moderate physical activity, have a calm life, and sufficient sleep duration.