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 nitroprusside effect. Averaged control data included a mean resistance of 1460 dyn-sec-cm-5 and a characteristic impedance of 88 dyn-sec-cm-5 The characteristic impedance did not correlate with age (r = 0.21), coronary artery disease score (r = 0.17) or mean aortic pressure (r = -0.01). In 11 patients, isoproterenol induced a 38% reduction in mean resistance and a 10% reduction in mean aortic pressure. There was slight reduction in characteristic impedance and phase angles became less negative, to 2 Hz. In seven patients, nitroprusside induced a 38% reduction in mean resistance and a 22% reduction in mean aortic pressure. Impedance moduli decreased to 1.8 Hz and phase angles became less negative, to 3 Hz. Based on the different cardiovascular actions of these two drugs, the data suggest that vasodilators do not induce significant changes in the aortic impedance spectrum when not associated with a decrease in mean aortic pressure.
D000328:Adult; D000787:Angina Pectoris / Q000188:drug therapy; D001011:Aorta / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects; D002307:Cardiography, Impedance; D005260:Female; D005292:Ferricyanides / Q000627:therapeutic use*; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007545:Isoproterenol / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009599:Nitroprusside / Q000627:therapeutic use*; D013318:Stroke Volume / Q000187:drug effects; D014665:Vasodilator Agents / Q000627:therapeutic use*
D005292:Ferricyanides; D014665:Vasodilator Agents; D009599:Nitroprusside; D007545:Isoproterenol