The lymphatic drainage of the pericardial space in the dog

The purpose of this study was to characterize definitively the lymphatic drainage system of the pericardial space in the dog. The reports on this subject, based on dissection experiments and acute dye injections, remain controversial, and our own previous studies have been incomplete. Seventeen dogs were studied using a radiographic technique. Micropulverized barium sulfate instilled into the pericardial sac was followed with serial chest x-rays in seven dogs with intact cardiac lymphatics, in seven dogs after section of the cardiac lymphatic drainage node (the cardiac lymph node) in the right upper mediastinum, and in three dogs after resection of cardiac drainage lymphatic nodes in the left upper mediastinum. These studies revealed that the lymphatic drainage of the pericardial space is via (a) the principal coronary lymphatic which drains from the left ventricular muscle and passes to the right upper mediastinum via the cardiac lymph node, (b) the lesser coronary lymphatic which drains the right ventricular muscle and passes to the left upper mediastinum, and (c) bilateral internal mammary (parasternal) lymphatic chains. These observations are important in planning experimental approaches to the effects of impairment of lymph drainage from the pericardial space. An understanding of the lymph drainage from the pericardial space may prove significant to understanding fibrotic reactions within it and the pathologic mechanisms of such entities as constrictive pericarditis.