Light microscopy of the lymphatics of the human atrial wall and lymphatic drainage of supraventricular pacemakers

After injection of Indian ink stained 2% gelatine in 42 human hearts the lymph drainage of the regions of supraventricular cardiac pacemakers and the patterns of the lymphatic vascular bed in the atrial wall were studied. From the sites of the pacemakers the lymph is drained into the tracheobronchial nodes in 100%. Only two of those regions are drained through additional pathways, namely the SAN region into the anterior mediastinal node situated at the azygos vein and the coronary sinus area into the anterior mediastinal lateropericardiac nodes. In the cleared specimens as microscopically the epicardial lymph vessels produce polygonal superficial network; oblique anastomoses of that network run into the deeper layers of subepicardial tissue where they join with deep irregular lymphatic network. Deep subepicardial lymph vessels are often accompanied by veins and nerves. The course of most of myocardial lymph vessels follows the position of muscle cells. In the connective septa these vessels join to form larger trunks and open into the subepicardial vessels.