Improving the procedural safety and efficacy of radiofrequency catheter ablation for atrial fibrillation. Studies with special focus on non-paroxysmal atrial fibrillation
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Introduction: Atrial fibrillation (AF) is the most common sustained arrhythmia, and it is responsible for increased mortality and a reduced quality of life. Its prevalence is rapidly increasing. Catheter ablation has emerged during the past decade as a promising treatment option for paroxysmal and non-paroxysmal AF patients. We investigated various aspects of catheter ablation for AF, particularly in non-paroxysmal AF, with the aim of improving the safety and efficacy of such procedures.
Aims and methods: The patients enrolled in these studies were burdened by symptomatic, drug-refractory AF. Non-paroxysmal AF was the clinical arrhythmia in the majority of the individuals. All patients underwent an electrophysiological study and subsequently an ablation procedure that included pulmonary vein isolation and in selected cases, complex fractionated electrogram (CFE) ablation. The first study aimed to assess long-term outcomes in a population of exclusively non-paroxysmal AF patients who were followed up regularly for an average of 40 months. In the second study we investigated the effects of flecainide on the distribution and extension of CFE areas. For this purpose, two separate CFE maps (before and after flecainide administration) were created and compared. In the third study we assessed the correlation between catheter-tissue contact force and impedance fall. Qualified ablation points were selected and the corresponding contact force and impedance fall data were retrieved and analyzed.
Results and conclusions: An approach consisting of pulmonary vein isolation and CFE ablation appears to provide favorable long-term outcomes in a high proportion of patients. Multiple procedures are often required to attain positive results. Although post-ablation atrial tachycardia frequently occurs, it may represent a step towards long-term success. Longer AF duration and female gender appear to predict a higher likelihood of procedural failure.
Intraprocedural administration of flecainide in non-paroxysmal AF patients reduces the extension of CFE areas but preserves their original localization. The employment of a CFE-mean cut-off of 80 ms may facilitate the identification of stable CFE areas. The CFE areas that thus disappear may be functional and therefore may be an inappropriate target for ablation.
Increasing degrees of catheter-to-tissue contact force lead to a larger impedance fall suggesting improved lesion formation. Under stable catheter conditions, a contact force greater than 5 g seems to create adequate lesions. However, a contact force beyond 20 g is associated with late impedance rise, and may be a warning of an increased risk of complications.