Histological And Electrophysiological Characteristics Of The Ectopic Focus Of Focal Atrial Fibrillation Originating From Ligamet Of Marshall And Myocardial Sleeve Of Pulmonary Vein

Atrial fibrillation(AF) is one of the most common and complicated arrhythmia and can lead to cardiac function injury. AF has high mortality and morbidity because the patients with AF are inclined to thrombus forming in atria. The cardiologists always try to find out a method by which they can restore the sinus rhythm of the patients with AF but not decrease the function of the patients? hearts. So, they have studied the mechanism of AF untiringly and treated AF by various methods. COX maze procedure was reformed continuously and the rate of success has reached over 90%. Great success was won with radiofrequency ablation when treating various tachycardia, so radiofrequency ablation was considered as a method used to deal with AF. Recently, one kind of AF(focal AF) has been cured with radiofrequency ablation. But, many problems have not been solved during treating this kind of AF. For example, the rate of provocation of focal AF is low, but recurrence is high and it is difficult to judge the end point of ablation. The reason is that we are still not clear about the mechanism of focal AF. The aim of this experiment was to investigate the role of ligament of Marshall and pulmonary vein by examinating their electrophisological characteristics and observing their histological features. The experiment consisted of two sections;(l) After the electrophysiologic examination was performed, the atrial tissue block containing ligament of Marshall was used to examine the histological features. Then, we analysed the relation between the result of histological observation and the result of the electrophysiologic examination. The result of the first section suggested that: Double potential(LAM potential and LOM potential) was recorded at ligament of Marshall from 6 dogs of 8 dogs. The internal of HRA and LAA and the internal of HRA and LAM did not change apparently, but LQM potential disappeared after ablating the part of LOM near coronary sinus; Morphologic observation suggested that there was cardiac muscle in the ligament of Marshall, the cardiac muscle in the ligament of Marshall was separate from the deeper left atrial muscle by fatty tissue and the gap contained some nervous tissue. (2) The tissue block containing the posterior wall of the left atrium and all of pulmonary veins were cut off and were used to examine the histological features. The result of the second section suggested that: ?The pulmonary vein walls of dogs were composed of 3 layers: the tunica intima, tunica media and tunica adventitia. The tunica media was the myocardial sleeve extending into pulmonary vein. The myocardial sleeve in the superior pulmonary vein was longer than it in the inferior pulmonary vein. The course of myocardial fibre was irregular; P-like cells different from common myocardial cells were found in the pulmonary veins and P-like cells scattered in the myocardial sleeves of pulmonary veins. CONCLUSIONS:LOM potential originates from the myocardial muscle in LOM. Ablation on the part of LOM near the CS doesn't influence conductionbetween left and right atrium. 0 Ectopic beats from pulmonary veins triggering atrial fibrillation may be the results of P-like cells in the myocardial sleeves in the pulmonary vein.