Cardiac arrhythmias are alterations in the sequence of contractions and relaxation of the heart. Its causes can be diverse, as well as its severity and clinical consequences: some arrhythmias remit spontaneously, while others significantly cardiac function thereby putting the patient in danger of serious complications. Generally, treatment is only requested if the arrhythmia causes important symptoms or if it generates risks of suffering a more serious arrhythmia or a complication. It is important to know that the treatment for cardiac arrhythmias will depend on the type of arrhythmia and on each patient, since each patient and each arrhythmia are unique.
Non-pharmacological treatment of cardiac arrhythmias
• Pacemakers: the definitive pacemaker is a device that allows the heart to be stimulated at programmable frequencies. It consists of one, two or three wires that are placed intravenously in the right atrium (RA), right ventricle (RV) or through coronary sinus to stimulate the left ventricle (LV), these wires are connected to a generator that is placed subcutaneously in the infraclavicular area. They are used in case of symptomatic bradyarrhythmias (slow heart rate), usually caused by sinus node dysfunction or atrioventricular block. There are also transient pacemakers, with a temporary electrode that allows their subsequent removal, and transcutaneous pacemakers, which allow stimulation by skin patches, and which are used in emergency situations or in processes that cause bradycardia and are reversible (medications, ionic disorders, etc.).
• Implantable automatic defibrillator: There are implantable devices that can detect and treat malignant ventricular arrhythmias, so that they prevent sudden death in patients who have already had an arrhythmic event or are at risk of suffering it (dilated, hypertrophic cardiomyopathy, channelopathies, etc.). Arrhythmias can end with overstimulation (stimulating more frequently) or by electric shocks. They are implanted intravenously, such as pacemakers, and they also have a stimulation function for bradycardia.
• Radiofrequency ablation: through the use of catheters temporarily, an energy form of radiofrequency can be applied by endovascular route that heats the tissues at a controllable temperature to "destroy" the foci involved in the origin of the tachycardia.
Pharmacological treatment of arrhythmias
The antiarrhythmic drugs are classified according to their mechanism of action in:
• Class I: act on the sodium channels blocking them. Some increase the duration of the action potential, some delay it and others narrow it.
Ø IA: increase repolarization (quinidine, procainamide, disopyramide). Procainamide is used in the treatment of extrasystoles and ventricular tachycardias.
Ø IB: decrease repolarization (mexiletine, lidocaine, tocainide). Lidocaine was widely used in patients in the acute phase of infarction when they had many premature beats, which was considered a mortality marker because they could produce ventricular arrhythmias and death. But several studies showed, with this measure, patients died more frequently. Now it is only used in ventricular arrhythmias when a certain degree of ischemia is suspected, but not in the case of extrasystoles. Mexiletine is no longer used. The tocainide no longer exists.
Ø IC: increase repolarization (flecainide, propafenone, encainide). Today medications of the IC group (especially flecainide and propafenone) are used almost exclusively. A problem of these drugs is that they increase mortality in patients with heart disease, especially with depressed ventricular function (because they produce arrhythmias).
• Class II: beta-blockers (atenolol, propranolol, bisoprolol, carvedilol). They act by blocking the effect of the catecholamines, thus decreasing the automatism, causing bradycardia. It greatly affects the autonomic nervous system: it eliminates vegetative symptoms such as tremor or sweating. They are also used in other diseases such as heart failure and ischemic heart disease, hypertension. This shows the importance of beta-blockers in cardiology.
• Class III: are blockers of potassium channels, so they increase repolarization (amiodarone, sotalol, dofetilide). They have very varied effects. Amiodarone is the most used for arrhythmias, especially in the emergency department, because unlike all others (except beta-blockers), this drug is safe. In the studies carried out, it shows no adverse effects in terms of increased mortality. Therefore it can be used in patients with associated heart disease and with ventricular dysfunction.
• Class IV: calcium channel blockers (verapamil, diltiazem). They are also used in ischemic heart disease and high blood pressure (HBP). There are more calcium-blocking drugs (amlodipine and nimodipine, among others), although these do not have antiarrhythmic properties. They act mainly in the calcium-dependent cells, decreasing the rate of ascent of the action potential, thereby decreasing the automatism and slowing the conduction at the level of the ventricular atrial node.
Surgical treatments
In some cases, surgery may be the recommended treatment for cardiac arrhythmias:
Labyrinth procedure: In the labyrinth procedure, a surgeon makes a series of surgical incisions in the heart tissue in the upper half of the heart (atria) to create a pattern or a labyrinth of scar tissue. Because this scar tissue does not conduct electricity, it does avoid the isolated electrical impulses that cause some types of arrhythmia.
The procedure is effective but, as it requires surgery, it is usually reserved for people who do not respond to other treatments or for those who undergo heart surgeries for other reasons.
Sources
1. Wellens HJJ. Electrical Stimulation of the Heart in the Study and Treatment of Tachycardias. Baltimore: University Park Press, 1971
2. Anastasiou-Naza MJ, Anderson JL, Stewart JR, et al. Occurrence of exercise induced and spontaneous wide complex tachycardia during therapy with Recainide for complex ventricular arrhythmias: a probable proarrhythmic effect. Am Heart J 1987.
3. Lezaun R, Brugada P, Talajic M, et al. Cost-benefit analysis of medical versus surgical treatment of symptomatic patients with accessory atrioventricular pathways.
4. Kasper, D. and Harrison, T. (2005). Harrison's principles of internal medicine. New York: McGraw-Hill, Medical Pub. Division.