Abstract
Dynamic arterial elastance (Eadyn), the ratio between arterial pulse pressure and stroke volume changes during respiration, has been postulated as an index of the coupling between the left ventricle (LV) and the arterial system. We aimed to confirm this hypothesis using the gold-standard for defining LV contractility, afterload, and evaluating ventricular-arterial (VA) coupling and LV efficiency during different loading and contractile experimental conditions. Twelve Yorkshire healthy female pigs submitted to three consecutive stages with two opposite interventions each: changes in afterload (phenylephrine/nitroprusside), preload (bleeding/fluid bolus), and contractility (esmolol/dobutamine). LV pressure-volume data was obtained with a conductance catheter, and arterial pressures were measured via a fluid-filled catheter in the proximal aorta and the radial artery. End-systolic elastance (Ees), a load-independent index of myocardial contractility, was calculated during an inferior vena cava occlusion. Effective arterial elastance (Ea, an index of LV afterload) was calculated as LV end-systolic pressure/stroke volume. VA coupling was defined as the ratio Ea/Ees. LV efficiency (LVeff) was defined as the ratio between stroke work and the LV pressure-volume area. Eadyn was calculated as the ratio between the aortic pulse pressure variation (PPV) and conductance-derived stroke volume variation (SVV). A linear mixed model was used for evaluating the relationship between Ees, Ea, VA coupling, LVeff with Eadyn. Eadyn was inversely related to VA coupling and directly to LVeff. The higher the Eadyn, the higher the LVeff and the lower the VA coupling. Thus, Eadyn, an easily measured parameter at the bedside, may be of clinical relevance for hemodynamic assessment of the unstable patient.
Highlights
Dynamic arterial elastance, the ratio between pulse pressure variation (PPV) and stroke volume variation (SVV), defines the relationship between the changes in the arterial pulse pressure and stroke volume (SV) during a respiratory cycle (Pinsky, 2006)
Other factors not related to the arterial system have been involved in the subsequent dynamic arterial elastance (Eadyn) value, for example, heart rate and blood flow acceleration have been associated with changes in Eadyn (Monge Garcia et al, 2017a)
The study was approved by the Institutional Animal Care and Use Committee (IACUC) at the Edwards Research Center, and all procedures were performed in accordance with the USDA Animal Welfare Act regulations (AWArs), and the Guide for the Care and Use of Laboratory Animals (ILAR, NAP, Washington, DC, United States, 2010, 8th edition)
Summary
The ratio between PPV and SVV, defines the relationship between the changes in the arterial pulse pressure and SV during a respiratory cycle (Pinsky, 2006). Other factors not related to the arterial system have been involved in the subsequent Eadyn value, for example, heart rate and blood flow acceleration have been associated with changes in Eadyn (Monge Garcia et al, 2017a) How these arterial and cardiac factors affect to PPV and SVV would define Eadyn. These potentially contradictory findings led to propose that Eadyn may represent an index of the coupling between the heart and the systemic circulation (Pinsky, 2006; Monge Garcia et al, 2017a). We analyzed the impact of various maneuvers known to affect vasomotor tone, contractility and volume status on both VA coupling and Eadyn
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