Abstract 17472: Changes in the Vascular Properties, Not the Ventricular Properties, Predominantly Contributes to the Baroreflex Induced Arterial Pressure Regulation
Background: Baroreflex (BR) modulates both the ventricular and vascular properties, and feedback regulates arterial pressure (AP). However how changes in those mechanical properties quantitatively impact the dynamic AP regulation remain unknown. We recently developed a framework of circulatory equilibrium (Am J Physiol 2004, 2005) where we algebraically expressed both venous return and cardiac output as functions of left ventricular (LV) end-systolic elastance (Ees), heart rate (HR), systemic vascular resistance (R) and stressed blood volume (V). We investigated if the extended Guyton’s model can quantitatively predict the AP responses on the basis of BR induced dynamic changes of ventricular and vascular properties.
Methods and Results: In 6 anesthetized dogs, we vascularily isolated carotid sinuses and randomly changed carotid sinus pressure (CSP) by a servo-pump, while measuring the beat-to-beat LV Ees (Millar and sonomicrometry), aortic flow (Transonic) and AP for 60 minutes. We estimated transfer functions from CSP to HR, Ees, R and V using the initial half of time series data in each dog. We then predicted those parameters with the transfer functions in response to changes in CSP using the last haft of time series data and synthesized changes in AP using the equilibrium framework. Synthesized AP matched reasonably well with those measured (r2=0.81-0.95, p<0.001, Figure). Sensitivity analyses indicated that Ees and HR (ventricular properties) accounted for 17±8% and <1%, respectively, whereas V and R (vascular properties) accounted for 34±6% and 35±9%, respectively, of BR induced AP regulation.
Conclusion: The BR induced dynamic AP changes can be accurately predicted by the transfer functions from CSP to ventricular and vascular properties with the framework of circulatory equilibrium. Changes in the vascular properties, not the ventricular properties, predominantly determine the BR induced AP regulation.
- © 2013 by American Heart Association, Inc.