Influence of the pericardium on left ventricular end-diastolic pressure-segment relations during early and later stages of experimental chronic volume overload in dogs.

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Abstract
Although the pericardium can exert a restraining effect on filling of the normal left ventricle, it is uncertain to what extent the pericardium influence left ventricular filling during chronic volume overload. Left and right ventricular pressure and left ventricular segment dimension were measured before and after pericardiectomy over a range of left ventricular end-diastolic pressure from .ltoreq. 5 to .gtoreq. 20 mm Hg in open-chest dogs with volume overload due to a prior systemic arteriovenous fistula. In 6 dogs studied early (7-9 days) during volume overload, left ventricular end-diastolic dimension was significantly larger and right ventricular end-diastolic pressure lower following pericardiectomy at matched levels of left ventricular end-diastolic pressure greater than 10-12 mm Hg. In 6 dogs studied late (34-50 days) during chronic volume overload, there were no significant changes in left ventricular end-diastolic dimension after pericardiectomy at comparable levels of end-diastolic pressure. To account for the influence of changes in right ventricular end-diastolic pressure after pericardiectomy, left ventricular end-diastolic dimensions before and after pericardiectomy at matched corrected left ventricular end-diastolic pressure [(left ventricular end-diastolic pressure) - (right ventricular end-diastolic pressure .times. interventricular septal surface area/total left ventricular surface area)]. This correction of the left ventricular end-diastolic pressure did not significantly alter the results in either the early or late group. Restraint to filling by the pericardium in this model of volume overload is present early but becomes markedly diminished during later phases.