Hybrid therapy of atrial fibrillation.
Antiarrhythmic drugs have shown a poor long-term efficacy in the management of atrial fibrillation. It has been suggested that the association of antiarrhythmic drugs and non-pharmacological treatments may be superior to the prescription of a single treatment only. Electrical cardioversion of atrial fibrillation can be ineffective in several cases (long-lasting atrial fibrillation, large atria, advanced age, underlying diseases, high transthoracic impedance): the prescription of antiarrhythmic drugs prior to electrical shock has been demonstrated to be able to increase the success rate and to reduce the energy requirement. Ibutilide, amiodarone and sotalol are the most effective, while the efficacy of class IC drugs is controversial. The use of conventional atrial stimulation in case of the brady-tachy syndrome is related to the need of sustaining the atrial rhythm during bradycardia which can be exacerbated by the use of antiarrhythmic drugs. New overdrive algorithms, such as consistent atrial pacing and atrial rate stabilization, can increase the efficacy of physiological pacing. Painless electrical therapies, such as ramp and burst, have been implemented in specific devices, in order to combine the prevention and treatment of atrial arrhythmias. Multisite atrial stimulation has been introduced to improve the activation sequence and to reduce atrial asynchrony in case of slow conduction in the right atrium and of retrograde activation of the left atrium. Two methods are available for multisite atrial pacing: 1) simultaneous biatrial stimulation with the leads placed in the right appendage and in the left atrium through the coronary sinus; 2) dual site right atrial pacing with the leads positioned in the roof of the right atrium and proximal to the ostium of the coronary sinus. Single site non-conventional atrial pacing with the lead placed at the level of the interatrial septum, in the triangle of Koch, has been proposed in order to modulate the anisotropic conduction of this zone, responsible for the onset of atrial fibrillation. Non-conventional stimulation in association with drug therapy has been demonstrated to be more effective than conventional pacing in reducing the incidence of paroxysmal atrial fibrillation. The use of a dual-chamber defibrillator equipped with painless antitachy pacing therapies and atrial cardioversion can be considered the next step in the evolution of implantable devices. Atrioventricular nodal ablation and pacemaker implantation (ablate and pace) has been the first radiofrequency ablation procedure used to control the atrial fibrillation rate. Recently, it has been demonstrated that the survival rate in these patients was similar to that observed in subjects who received antiarrhythmic therapy. In patients in whom the administration of antiarrhythmic drugs (mainly class IC or amiodarone) modified atrial fibrillation in atrial flutter, linear lesions on the isthmus have been demonstrated to be effective in inhibiting the recurrence of arrhythmia. The first approach attempted in order to directly treat atrial fibrillation was the creation of linear lesions in the right atrium by means of radiofrequency current in patients refractory to drug therapy. This procedure was found to be feasible and safe, while lesions on the left atrium were associated with a high rate of side effects. The aim of the lesions was to create block lines in intra-atrial conduction, in order to electrically compartmentalize the atria and to avoid the propagation of reentry waves. More recently the ablation of the automatic activity originating from the posterior wall of the left atrium or within the pulmonary veins, which can trigger the onset of atrial fibrillation, has been performed.[1]References
- Hybrid therapy of atrial fibrillation. Santini, M., Pignalberi, C., Ricci, R., Calò, L. Italian heart journal : official journal of the Italian Federation of Cardiology. (2002) [Pubmed]
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