Cardiac lymphatic obstruction: ultrastructure of acute-phase myocardial injury in dogs.

Cardiac lymphatics exist as a network of intercommunicating channels in the myocardium and heart valves, and chronic obstruction of these vessels may result in endomyocardial fibrosis and mucoid degeneration of heart valves. The acute effects of experimental cardiac lymphatic obstruction were studied in the dog. Subendocardial edema and hemorrhage occurred within 150 minutes of the ligation of cardiac lymphatics. Ischemia-type myocardial injury was also observed. Attional changes detectable ultrastructurally included lymphangiectasia, myofibrillar degeneration, disruption of Z-band and intercalated disks, and various mitochondrial derangements. The spottiness of the changes was attributable to the known anatomic variability of lymphatic distribution in the heart. The findings reinforce the belief that greater attention should be focused on the role of cardiac lymphatics in the pathogenesis of a multitude of myocardial and vavular heart diseases.