Purpose: This study was performed to characterize the dynamic factors determining ventricular interdependence in an open-pericardium intact animal model. Materials and Methods: Simultaneous measures of right ventricular (RV) and left ventricular (LV) pressures and volumes in 6 urethane-anesthetized open-chested, open pericardium rabbits. RV and LV V were calculated every 2 milliseconds. Measurements were made at initial baseline blood volume, and again after two infusions of 20 mL/kg isoconductive colloid solution. At each blood volume level, partial aortic (AO), pulmonary artery (PAO), and inferior vena caval (IVC) occlusions were performed. Biventricular diastolic compliance and end-systolic elastance were calculated from these data. Results: Baseline end-diastolic (ED) and end-systolic (ES)V were 3.29 ± 0.55 and 2.43 ± 0.33 mL (x ± SD) for the LV, and 3.38 ± 1.56 and 2.84 ± 1.36 mL for the RV, respectively. AO increased all LV pressure and volume (P <.05) but did not alter RV ED volume (2.85 ± 1.20 mL) or ED pressure (3.3 ± 2.0 to 3.6 ± 2.1 mm Hg). PAO increased RV ES pressure (P <.05) but did not alter RV ED volume, ED pressure, or ES volume, although it decreased LV ED volume (2.82 ± 0.59, P <.05). AO also immediately increased end systolic RV elastance to a value greater than that defined by IVC (7.9 ± 4.4 to 10.9 ± 6.6 mm Hg/mL,P <.05). Intra-vascular volume expansion though increasing baseline pressure and volume, did not alter qualitatively biventricular responses to AO, PA, or IVC. Conclusion: Ventricular interdependence has both systolic and diastolic components that have differing directional effects. In the pericardectomized rabbit, increases in RV ED volume decrease LV ED volume by decreasing LV diastolic compliance, but do not alter LV systolic function. Whereas, increases in LV ED volume decrease RV ES volume resulting in an increase in RV maximal elastance, but minimally alter RV diastolic function.
ASJC Scopus subject areas
- Critical Care and Intensive Care Medicine