Antiarrhythmics And Their Appropriate Combinations

Regardless of the arrhythmia being treated, the goals of antiarrhythmic therapy are to control symptoms and improve survival.

Antiarrhythmics are drugs used for  the symptomatic and preventive treatment of deterioration of heart function  due to tachycardia and irregular rhythm.

They work by modifying the automatism,  refractory periods and conduction speed of heart cells. However, the goals of antiarrhythmic drug therapy are to control symptoms and improve survival.

The efficacy of antiarrhythmics is however moderate and  they have a narrow therapeutic margin. In some cases, they can even be lethal if not used properly.

Types of antiarrhythmics

Based on their main mechanism of action, antiarrhythmics can be classified as follows:

Class I antiarrhythmics

Antiarrhythmics in this group work by blocking sodium channels. Among them, the most used are flecainide and propafenone.

They can be dangerous in patients with certain types of heart problems, especially if they have suffered from a heart attack or depression of cardiac contraction function.

Depending on its characteristics, this group is divided into:

• Class IA:  includes disopyramide and procainamide, with intermediate kinetics. They work by prolonging the duration of the action potential, repolarization, and the PR, QRS and QT intervals.
• Class IB:  lidocaine and phenytoin. These drugs have rapid kinetics and reduce the action potential. They can also reduce repolarization and the QT interval.
• Class IC:  these are the most used. They have slow kinetics and do not greatly affect the action potential and repolarization. However, they prolong PR and QRS and show no effect on QT.

Class II antiarrhythmics

In this group, we find beta blockers. The most widely used are atenolol, propanolol, metoprolol and bisoprolol.

We can emphasize their bradycardizing effect, that is to say the reduction of the heart rate on the sinus node and the atrioventricular node. These drugs can be used in patients with and without structural heart disease.

Class III antiarrhythmics

This group works by blocking the potassium channels. The most widely used are amiodarone and sotalol. Amiodarone is relatively safe in patients with structural heart disease.

Structural heart disease refers to a series of different cardiovascular conditions that are  nevertheless related because they all arise from the same problem. For example, an interruption in the natural flow of blood through the internal chambers and valves of the heart.

Regarding amiodarone, you should know that it has frequent and / or serious extracardiac side effects. For example, it can produce toxicity in the thyroid glands and in the lungs.

Class IV antiarrhythmics

Class IV antiarrhythmics work by blocking calcium channels. Among them, the most widely used are verapamil and diltiazem.

Even if they are not very powerful as antiarrhythmics, they have bradycardizing properties, acting mainly on the sinus and atrioventricular node. They can be dangerous in patients with depression of cardiac contractile function.

Other drugs

There are two other medicines which do not belong to any of the groups mentioned and which  are also used in the treatment of arrhythmias.

• Digoxin:  it acts by shortening the atrial and ventricular refractory periods. In addition, it has vagotonic properties, which makes it possible to prolong conduction and refractory periods in the atrioventricular node.
• Adenosine:  It reduces speed or blocks conduction in the atrioventricular node. It can also reverse conduction-dependent tachycardias through the atrioventricular node.

Indications for antiarrhythmics

Antiarrhythmics are recommended to treat the following:

• End or control an episode of arrhythmia.
• Prevent recurrence of arrhythmia.
• Avoid the occurrence of severe arrhythmias in specific situations.

They are also indicated in certain documented tachycardias , depending on their efficacy, safety and proven benefit. In these situations, they are used to relieve symptoms, improve heart performance, and prevent degeneration to malignant arrhythmia.

When the patient has sustained supraventricular tachycardia, amiodarone, verapamil, digoxin and adenosine are used. On the other hand,  if there is ventricular tachycardia, intravenous lidocaine is used. It will be given during myocardial ischemia (intravenous amiodarone can also be used).

In addition, to depress atrioventricular conduction, digoxin, beta-blockers, verapamil and amiodarone are administered. When one needs to remove extrasystoles, one uses lidocaine. However, to prevent supraventricular and ventricular tachycardias, flecainide, amiodarone and beta-blockers are used.

Conclusion

Even if cardiac ablation techniques have developed a lot,  the selection of treatment is conditioned by the type of arrhythmia and the profile of the patient,  especially if there is a basic heart disease.