Novel surgical approach to left ventricular diastolic dysfunction: an acute volume overload rat model

Left ventricular diastolic dysfunction frequently complicates cardiac surgery, primarily driven by perioperative acute volume overload (AVO). This study aimed to establish a novel surgical rat model that recapitulates AVO-mediated left ventricular diastolic dysfunction for translational research. Twenty male Sprague Dawley rats (6–8 weeks old) were equally and randomly divided into AVO group (intraventricular saline infusion at 3 ml/h) and Sham group (no fluid infusion). A 22-gauge cannula was inserted into left ventricle chamber to record pressure and inject fluid after left thoracotomy. Hemodynamic and echocardiographic statistics were obtained at baseline, 10 min, 20 min, 30 min and 40 min. Two-way repeated-measures analysis of variance (RM-ANOVA) was applied to compare longitudinal cardiac parameters, with Mauchly’s sphericity test and Greenhouse-Geisser correction for sphericity violation; Bonferroni post-hoc tests corrected for multiple pairwise comparisons. RM-ANOVA detected statistically significant main effects of group, time, and group×time interaction for LV systolic pressure (LVSP), LV diastolic pressure (LVDP), and LV end-diastolic pressure (LVEDP) (all P < 0.001). In the AVO group, LVEDP increased progressively over time, rising by 102.7% relative to baseline at the 40 min time point. Post-hoc testing confirmed substantially higher LVEDP in AVO rats versus sham animals at 40 min (15.2 ± 0.79 mmHg vs. 7.5 ± 0.71 mmHg, adjusted P < 0.001). A prominent group×time interaction was also observed for the mitral E/A ratio ( P < 0.001): this ratio declined to 0.54 in the AVO group at 40 min, which differed significantly from sham controls (0.54 ± 0.01 vs. 1.73 ± 0.01, adjusted P < 0.001). Left ventricular ejection fraction (LVEF) exhibited a significant group×time interaction as well, falling to 62.82% at 40 min in AVO rats compared with 76.34% ± 0.36 in sham animals (adjusted P < 0.001). All hemodynamic and echocardiographic readouts remained stable across all time points in the sham group, with no statistically significant temporal changes observed. Acute volume overload induced heart diastolic dysfunction in rats is a cost-effective and time-efficient experimental animal model. AVO: acute volume overload. LVEDP: left ventricular end diastolic pressure. E/A ratio, early (E) and late (A) diastolic transmitral Doppler flow velocities ratio. LVEF: Left ventricular ejection fraction.