Atrial fibrillation (AF) is the most frequent cardiac arrhythmia, with prevalence around 10% among population older than 70, and with increasing perspectives according to an increase in the quality of life. Despite being the most frequent cardiac arrhythmia, the exact mechanisms that generate and perpetuate AF still remain uncertain. For this reason, any study that improves current knowledge about AF and the effects of clinical treatment will be helpful for the development of clinical protocols that improve diagnose and selection of the most appropriate treatment. Scientists have inquired into what abnormal circumstances affecting the basic electrophysiologic state of the atria are responsible for the inception and perpetuation of fibrillation, and what factors govern the response of the atrioventricular transmission system. Among them, the Autonomous Nervous System has been proven to be one of the factors that affects atrial electrical activity. This doctoral thesis has studied the effect on atrial and ventricular activities of the most common anesthetic agent used in AF ablation and cardioversion therapies. This anaesthetic is propofol (2,6-diisopropylphenol), which is a rapidly acting intravenous anaesthetic. The rapid redistribution and metabolism of propofol results in a short elimination half-life of approximately one hour, making it suitable for short-lasting sedation. The hypothesis is that a propofol bolus might alter atrial electrical activity during AF. During AF ablation procedures, simultaneous atrial electrograms and electrocardiograms are recorded. Local electrograms may provide useful informationreflecting the electrophysiological processes during AF. Typically, intracardiac electrograms in AF show a high degree of spatiotemporal variation, reflecting the irregular and complex activation in the atria. In addition, respect to ventricular rhythm, although basic and experimental research has provided insight into the mechanisms of AF, as well as the effect of autonomous nervous system and many antiarrhythmic drugs, the ventricular response under the anesthetics effect during AF therapies have not been completely studied. The results support that propofol influences on both atrial and ventricular rhythms. More specifically, it has been observed an opposite effect in right and left atrium. Whereas atrial electrical activity increases the organization at the right atrium due to propofol administration, the organization of atrial activations is decreases at the left atrium. Moreover, significative changes in both ventricular and atrio-ventricular conduction rates were also detected.