Creep of the canine pericardium in vivo

In eight open chest dogs we assessed the creep of the pericardium by measuring the increase in surface area of the pericardium, occurring after pericardial surface pressure (Ppe) was rapidly increased by inflating an air-containing balloon positioned between the pericardium and the left ventricular (LV) epicardium. We observed an increase in LV end diastolic pressure (EDP) of 3.6 +/- 3.4 mmHg (1 mmHg = 133.3 Pa) (p less than 0.05) (mean +/- SD) and a reduction in LV anteroposterior (AP) diameter of 8.8 +/- 6.1 mm (p less than 0.01), both of which were stable after 10 s. Mean Ppe increased 11.6 +/- 3.3 mmHg (p less than 0.001). Pericardial surface lengths at 45 and 135 degrees to the long axis of the LV were measured with two pairs of ultrasonic crystals attached to the outer surface of the pericardium. The beam of ultrasound travelling between each pair was directed parallel to the pericardial surface through a film of conducting medium. Initial increase in surface area (calculated as the product of two pericardial lengths) occurring during the first 15 s after balloon inflation was 5.8 +/- 2.5% (p less than 0.001). During the next 30 min, while mean pericardial pressure did not change, pericardial surface area increased another 2.8% (p less than 0.005). This time-dependent 2.8% increase in pericardial surface area (equivalent to an increase in volume of approximately 5%) is due to creep.(ABSTRACT TRUNCATED AT 250 WORDS)