الفهرس 
Anatomy of the Conduction System
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Abstract
Many patients with mitral valve disease have concomitant atrial fibrillation (AF) which results in a variety of morbidities including hemodynamic compromise, syncope, dizziness, fatigue, palpitations, chest pain and an increased probability of a thromboembolic event.
At the time of mitral valve surgery the incidence of concomitant AF can reach up to . Mitral valve surgery alone usually does not abolish AF and the persistence of AF after surgery increases postoperative morbidity and mortality hence he need for an additional intervention to target the AF itself.
AF is initiated by rapid erratic electrical activity, most often arising from arrhythmogenic foci or triggers located in the muscular sleeves of pulmonary veins. This likely relates to the anatomic transition from pulmonary vein endothelium to left atrial endocardium; at this juncture, two types of tissue with different electrical properties are juxtaposed, and this may potentiate development of the disease. This observation mainly explains the pathogenesis of paroxysmal or lone AF however, for AF to be sustained and become persistent or permanent, macro-reentrant wavelets need to exist in the atrial musculature. This requires an underlying cardiopulmonary disease, a factor that is absent in lone AF.Surgery for the treatment of atrial fibrillation culminated in the development of the Cox-Maze III, the Gold standard of treatment and still, the procedure with the highest success rate (up to according to some studies). However, it has not been widely adopted due to it’s complexity, it’s need for cardiopulmonary by-pass and it’s significant prolongation of by-pass time. Efforts have focused on developing a potentially less invasive and less time-consuming operation by simplifying the pattern of atrial lesions and using alternative energy sources that can create them quickly, without a cut-and-sew technique.
Intraoperative endocardial radiofrequency ablation to the pulmonary veins for atrial fibrillation is a promising new treatment option for patients with atrial fibrillation undergoing cardiac surgery or patients with highly symptomatic atrial fibrillation not responding to other therapies.
In our study on fourty patients saline-irrigated cooled tip radiofrequency endocardial ablation right after left atriotomy and before mitral valve surgery had good outcomes (almost success rate at months post-operatively) despite rheumatic etiology, large left atrial diameters and long AF duration. We employed a simple and relatively short procedure that focused exclusively on the left atrium taking into account the main lines of the maze operation. Circumferential pulmonary vein ostial isolation was of paramount importance of course. Antiarrhythmic medical therapy was used for months post-operatively.The success rate of the left-sided RF maze is close to that of the bi-atrial RF maze reported in other studies with a major difference being the much longer duration of the latter. That, and the virtual absence of major complications make it a valid and successful treatment option in the surgical management of the illness at the present moment until a shorter, more successful bi-atrial maze procedure can be developed in the future.
It is said that the pathology of AF of the remaining of patients that failed to restore SR originates in the right atrium so, again, until a more effective procedure that can target the right side as well is developed, the left-sided RF maze should be more widely used in clinical practice.