Response to Noninvasive Input Impedance of the Human Systemic Circulation

Noninvasive input impedance of the human systemic circulation.

Noninvasive Input Impedance of the Human Systemic Circulation To the Editor: The study of noninvasive aortic input impedance by Segers et al1 is a very important step in understanding age-related changes in humans and an advance on previous limited invasive studies conducted decades ago.2,3 One reason that these lapsed was the difficulty in accurately measuring aortic pulsatile flow, attributab...

Input impedance of the systemic circulation.

Input impedance of the systemic circulation in man.

To determine the systemic input impedance, pulsatile pressure and flow were measured in the ascending aorta in 16 human subjects who were undergoing diagnostic cardiac catheterization. Blood flow was measured with a catheter-tip electromagnetic velocity meter, and pressure with an external transducer connected with the fluid-filled lumen of the catheter. Five subjects were found to have no evid...

Response of the Systemic and Pulmonary Circulation

Labetalol (L), a drug with both aand fl-adrenoceptor blocking properties, was administered to 18 hypertensive patients for an average duration of 2.44 weeks, with an average final daily dose of 1.65 g. L decreased resting heart rate (HR) by 16% and maximal exercise HR by 21%; the phenylephrine-induced rise of brachial artery pressure (BAP) was reduced by 30-40%, and the rise of systemic vascula...

Aortic input impedance in man: acute response to vasodilator drugs.

In 18 patients who underwent coronary arteriography, aortic velocity and pressure data were obtained during a control state and during either isoproterenol infusion at 1, 2 and 3 micrograms/min or graded nitroprusside infusion (average peak dose 60 micrograms/min). Impedance moduli and phase angles were derived to 10 Hz for controls states, isoproterenol at 2 micrograms/min, and at peak nitropr...