Characterization of arterial hemodynamics in rats with established hypertension.

In long-term hypertension, hemodynamic alterations are associated with functional and structural changes in the cardiovascular system. The technique of arterial impedance spectral analysis has long been used to characterize the arterial hemodynamics of steady and pulsatile components in human hypertension. Although rats with spontaneous hypertension (SHR) are the most common model for studies of primary hypertension, characterization of complete hemodynamic parameters has not been accomplished in this animal model. In the present experiment, aortic flow and pressure waves were recorded in anesthetized, open-chest and ventilated rats. Arterial impedance spectral analysis was employed to obtain steady and pulsatile hemodynamic parameters. A total of 26 SHRs (22-24 wk) and 22 age-matched normotensive WKYs was used. The purpose was to provide a comprehensive analysis of arterial hemodynamics in rats with established hypertension. The SHR had higher arterial pressure (50% increase over the control) than WKY. The total peripheral resistance was elevated by 57%. Stroke volume was decreased by 23% and heart rate increased by 18% without a significant change in cardiac output. The characteristic impedance was increased by 43%, while arterial compliance was decreased by 52%. There were also big rises in ventricular work and wave reflection. The results provide quantitative analysis of the alteration in arterial hemodynamics of steady and pulsatile components in rats with established hypertension. In long-term hypertension, the hemodynamics reflect functional abnormalities in the resistance and Windkessel vessels.