title: Aortic impedance and hydraulic power in the chick embryo from stages 18 to 29.
abstract: Little is known about the hemodynamic properties of the rapidly expanding arterial bed during embryonic development. Using a servo-null pressure system and 20-MHz pulsed Doppler velocity meter, we recorded simultaneous dorsal aortic pressure and velocity waveforms. The waveforms were digitized at 3-msec intervals and subjected to Fourier analysis. We calculated hydraulic energy and the impedance spectrum to 10 Hz. From stages 18 to 29, heart rate (148 +/- 3 to 193 +/- 9 beats/min), systolic pressure (1.14 +/- 0.12 to 3.04 +/- 0.10 mm Hg), and mean dorsal aortic blood flow (21 +/- 2 to 214 +/- 19 mm3/min) increased. Peripheral vascular resistance (Z0: 30.4 +/- 4.8 to 6.4 +/- 0.7 dyne x sec/mm5), and the impedance moduli (Z1: 6.5 +/- 1.0 to 1.7 +/- 0.2 dyne x sec/mm5; Z2: 6.1 +/- 1.2 to 1.7 +/- 0.1 dyne x sec/mm5; Z3: 7.3 +/- 1.1 to 1.7 +/- 0.2 dyne x sec/mm5) decreased. Total hydraulic power increased from 48 +/- 7 to 2,606 +/- 96 nW, while the proportion of oscillatory energy increased from 29 +/- 2% to 65 +/- 4%. With development hydraulic load decreases, total external work increases and the dorsal aorta and embryonic vascular bed becomes more compliant. A greater proportion of total energy is expanded in pulsatile blood flow, suggesting that ventricular-arterial coupling is less efficient later in development.
authors.affiliation: Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: K G
authors.initials: KG
authors.lastname: Zahka
authors.forename: N
authors.initials: N
authors.lastname: Hu
authors.forename: K P
authors.initials: KP
authors.lastname: Brin
authors.forename: F C
authors.initials: FC
authors.lastname: Yin
authors.forename: E B
authors.initials: EB
authors.lastname: Clark
mesh_terms: D000818:Animals; D001011:Aorta / Q000196:embryology; D001775:Blood Circulation; D002319:Cardiovascular System / Q000196:embryology*; D002642:Chick Embryo / Q000254:growth & development / Q000502:physiology*; D006439:Hemodynamics; D014655:Vascular Resistance