Effects of perfusion-induced edema on diastolic stress-strain relations in intact swine papillary muscle.

The mechanism through which edema reduces left ventricular compliance has not been defined. Accordingly, diastolic properties of in situ left ventricular swine papillary muscles were studied in three groups: control (n = 6, 4 degrees to 6 degrees C), edematous (150 mOsm/L coronary perfusion, n = 6, 4 degrees to 6 degrees C), and ischemic contracture (n = 8, 28 degrees C). Lagrangian stress (sigma) and strain (epsilon) were calculated from slow stretch data and approximated by sigma = alpha(e beta epsilon-1). The natural logarithm of stress versus strain was linear over the physiologic range of 0.05 < strain < 0.40. Hypotonic perfusions (1 L x 3) progressively shifted the stress-strain relationship upward and to the left. Compared to baseline, alpha increased significantly (p < 0.05) after perfusion 3 (6.7 +/- 2.1 baseline, 12.2 +/- 6.6 perfusion 1, 12.7 +/- 3.5 perfusion 2, and 42.9 +/- 16.3 gm/cm2 perfusion 3). The constant beta did not change significantly (13.0 +/- 1.5 baseline, 13.1 +/- 1.6 perfusion 1, 13.2 +/- 1.6 perfusion 2, and 14.1 +/- 1.4 perfusion 3). Right ventricular water content increased after each perfusion (77.1% +/- 1.4% baseline, 81.6% +/- 1.3%, 84.7% +/- 1.5%, and 86.9% +/- 1.7%, p < 0.05). With ischemic contracture, alpha increased from 61.9 +/- 17.8 to 173.1 +/- 61.5 gm/cm2 (p > 0.05) and beta increased insignificantly from 6.5 +/- 0.6 to 10.6 +/- 1.8 (p = NS). In the control group all variables were unchanged after 210 minutes. We conclude that myocardial stiffness increases with myocardial edema. This may explain decreased compliance in the edematous left ventricle.