A novel technique for measurement of pericardial pressure

To determine whether pericardial liquid pressure accurately measures perica rdial constraint, we developed a technique in which a catheter was position ed perpendicular to the epicardial surface. This device, which occupies lit tle or no pericardial space, couples the thin film of liquid to a transduce r. In six open-chest dogs, we also measured left ventricular (LV) end-diast olic pressure (LVEDP) and anteroposterior and septum-to-free wall diameters . LVEDP was raised incrementally to similar to 25 mmHg by saline infusion. With the use of the product of the two diameters as an index of area (A(LV) ), LVEDP-A(LV) relationships were obtained with the pericardium closed and again after the pericardium had been widely opened to obtain the isovolumic difference in LVEDP (Delta LVEDP). In all dogs, the technique yielded valu es of pericardial pressure equal to Delta LVEDP as well as equal to that me asured using a previously placed balloon transducer in the same location an d at the same A(LV). We conclude that, when the pressure of the pericardial liquid is appropriately measured, it (in addition to the balloon-measured contact stress) defines the diastolic constraining effect of the pericardiu m. Furthermore, we suggest that earlier measurements of pericardial "liquid pressure" were low, due to an artifact of measurement.