The Significance of the Intact Pericardium for Cardiac Performance in the Dog

The significance of the intact pericardium for cardiac performance was examined in 18 open-chest dogs. Myocardial chord lengths (MCL) in the right and left ventricle were measured simultaneously by ultrasonic crystals implanted in the myocardium of the anterior walls. In 14 dogs, the ultrasonic elements were inserted into the myocardium through needle openings in the pericardium (intact pericardium). In four other dogs, the elements were inserted through 6-to 7-cm-long incisions in the pericardium which were sutured afterward (sutured pericardium). Stroke volume was calculated in each of seven dogs with an intact pericardium from electromagnetic measurement of flow in the superior and inferior venae cavae. After blood volume expansion to about 13 mm Hg, the pericardium was opened and the end-diastolic pressure-MCL relationships and stroke volumes before and after pericardiotomy were compared. By opening the intact pericardium, the right and left ventricular end-diastolic MCL rose by 2.7 ± 0.7± and by 3.7 ± 1.1±, respectively, and stroke volume increased by 13 ± 4±. However, by reopening the sutured pericardium, the increases in both right and left ventricular end-diastolic MCL were clearly greater (12.2 ± 5.6± and 9.9 ± 2.9±, respectively), and the restrictive effect of the pericardium was therefore overestimated when the pericardium was not left intact. Thus, after a moderate blood volume expansion, the intact pericardium exerts a certain, although moderate restrictive effect on cardiac performance. Circ Res 47: 27-32, 1980