The delayed effects of pericardial removal

Abstract The aim of these observations was to note such consequences, histological or other, as might ensue following removal of the fibrous pericardium. The development of cardiac changes being often slow, the pericardectomised cats were kept for considerable period (up to 17 months). In addition to recording the condition of the heart at necropsy, and on microscopic examination, radiograms of the normal and pericardectomised heart were made. Other lines of enquiry included direct inspection of the heart in situ under intra-tracheal ether, observation of the heart-rate, and some experiment on arterial and venous pressures. That the heart is very sensitive to pressure-changes within the pericardial sac is established. Lewis (11) conclusively showed in 1908 that so slight a rise in intra- pericardial pressure (in the cat) as 1 mm. lowers the systemic pressure by as much as 8 or 9 mm. of mercury. Conversely, a fall in intrapericardial pressure of 1 mm. induces a rise of some 8 to 9 mm. in the systemic pressure. The ill-effects of pericardial effusion—particularly when rapidly developed—are a clinical common-place ; once the intra-pericardial pressure comes to approximate that in the vena cava, the venous return to the heart is impeded and death may ensue (Williamson and Ets, 19, inter alia).