Myocardial edema: Comparison of effects on filling volume and stiffness of the left ventricle in rats and pigs

Background. This study compared the adverse effects of crystalloid-induced myocardial edema on left ventricular (LV) compliance in small and large hearts. Methods. Plegisol (289 mOsm/L) was perfused into the coronary arteries of pigs (n = 8) and 1:1 dilute Plegisol (145 mOsm/L) into the coronary arteries of rats (n = 6). Pressure-volume relations, heart weight, and water content were then determined. The pressure-volume relations were compared using an LV volume at a pressure of 10 mm Hg. Results. Edema in rats was associated with significant (p < 0.05) increases in heart weight (1.1 ± 0.0 g versus 1.4 ± 0.1 g [average ± standard error of the mean]) and water content (76.8% ± 0.4% versus 81.3% ± 0.8%), but an increase in LV stiffness (7.91 ± 0.52 versus 9.27 ± 1.42) and a decrease in the LV volume at 10 mm Hg (0.25 ± 0.02 mL versus 0.14 ± 0.05 mL) were not statistically significant. Edema in pigs was associated with statistically significant (p < 0.05) increases in LV stiffness β (0.050 ± 0.004 versus 0.072 ± 0.008), heart weight (207 ± 8 g versus 274 ± 9 g), and water content (79.8% ± 0.6% versus 85.3% ± 0.6%) and a significant decrease in the LV volume at 10 mm Hg (88.4 ± 5.8 mL versus 60.4 ± 6.8 mL). Conclusions. Myocardial edema is associated with an increase in water content and LV stiffness and a decrease in the LV volume at 10 mm Hg in both species. In rats, however, the water content is smaller in the control state and a more hypotonic perfusate is needed to induce a given degree of edema.