Diastolic properties, myocardial water content, and histologic condition of the rat left ventricle: Effect of varied osmolarity of a coronary perfusate

Background: Although myocardial edema is known to impair diastolic filling of the left ventricle, the interrelation of edema, histologic condition, and function has not been quantitated sufficiently for extrapolation to studies of multifactorial influences on diastolic properties. Methods: Accordingly, ACI rat hearts arrested at 4°C underwent coronary artery perfusion with a cardioplegia solution that was either unaltered (288 mOsm/L, P₂₈₈ group, n = 6), diluted (144 mOsm/L, P₁₄₄ group, n = 6), or concentrated (380 mOsm/L, P₃₈₀ group, n = 6). Postmortem left ventricular pressure-volume curves and myocardial water content were measured. Myocardial samples were fixed in varying dilutions of glutaraldehyde. After dehydration and paraffin embedding, edema was graded subjectively (0 to 5), and myocardial interstitial spaces were determined by use of a semiquantitative method. Results: Mean normalized left ventricular filling volume at 20 mm Hg filling pressure in the P₁₄₄ group, 189 ± 16 μl (SEM), was reduced versus both the P₂₈₈ (278 ± 26 μl) and the P₃₈₀ (332 ± 18 μl) groups (p < 0.05, ANOVA). Mean myocardial water content in the P₁₄₄ group, 80.7% ± 1%, was increased versus the P₃₈₀ (76.7% ± 0.4%, p < 0.05) but not versus the P₂₈₈ group (78.4% ± 0.8%). In hearts preserved with 2.5% glutaraldehyde, mean edema grade and interstitial space in the P₁₄₄ group (4.0 ± 0.3) were increased versus the P₃₈₀ (1.8 ± 0.3, p < 0.05) but not the P₂₈₈ group (2.7 ± 0.5). Derived linear regressions relate water content to filling volume and histologic condition. Conclusions: Coronary perfusate osmolarity is thus associated with predictable changes in myocardial water content, left ventricular filling volume, and edema. These correlations allow definition of new hypotheses for the study of cardiac allograft rejection in patients and experimental animals.