Independence of changes in left ventricular diastolic properties of pericardial pressure

There has been much interest in the published reports as to the extent to which measured left ventricular diastolic properties are affected by the pericardium. In this study observations were made on 24 patients, 7 days after cardiopulmonary bypass. Left ventricular dimensions were measured from echocardiographic recordings and left ventricular diastolic pressure assessed from measurements of isovolumic relaxation time. Pericardial pressure was measured directly using a small solid state transducer inserted into the pericardial space at the time of operation. Left ventricular diastolic properties were altered by either isometric handgrip or glyceryl trinitrate administration. Isometric handgrip produced an increase in cavity dimension at end-systole and diastole, with reduction in isovolumic relaxation time, suggesting an increase in left ventricular end-diastolic pressure; glyceryl trinitrate produced the reverse effect, with decreased cavity dimensions and prolongation of isovolumic relaxation time. These changes occurred in the absence of significant changes in pericardial pressure. The authors therefore conclude that even in the rather unusual conditions of the early postoperative period, when the sensitivity of pericardial pressure to small volume changes might be expected to be increased, substantial changes in left ventricular diastolic properties can occur without detectable alteration in pericardial pressure.