Study of underlying mechanism of chronic atrial fibrillation and development of new less invasive surgery

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To examine the electrophysiological characteristics of chronic atrial fibrillation associated with valvular disease, electrical activity of atrial fibrillation was mapped on the atrial surface by means of multi-point electrodes and specially made mapping system. Data were mainly acquired from the atrial free wall of both atria and anatomical obstacles, such as the orifice of pulmonary veins, and were analyzed using specially designed software. In this study, "macroreentry" was not detected but other new propagation patterns were found. Using spectral analysis, electrophysiological difference was noted between both atria. These findings suggest that early activation occurred from the left atrium and propagated to the right atrium and thus chaotic activation pattern was formed in the right atrium because of unequal refractory period on the right atrium.We developed a new, more simple surgical procedure, named as "pulmonary vein orifice isolation procedure", based on these electrophysiological findings. To eliminate chronic atrial fibrillation, we performed this procedure associated with mitral valve surgery and successfully set these patients, then, more than 80% of these free from atrial fibrillation postoperatively. Large left atrial dimension and long duration of preoperative atrial fibrillation was the predictive factor for the recurring atrial fibrillation. Small difference of electrophysiological status in both atria also predicted postoperative outcome. From the echocardiographic examination, posloperative cardiac performance was excellent in those cases who regained sinus rhythm and left atrial kick in the transmitral flow was observed in the majority of those patients.