18 research outputs found
Hemodynamics and Heart Function in the Venous Clipped Chick Embryo: The influence of volume blood flow on cardiac development
Acutely altered hemodynamics following venous obstruction in the early chick embryo
In the venous clip model specific cardiac malformations are induced in the
chick embryo by obstructing the right lateral vitelline vein with a
microclip. Clipping alters venous return and intracardiac laminar blood
flow patterns, with secondary effects on the mechanical load of the
embryonic myocardium. We investigated the instantaneous effects of
clipping the right lateral vitelline vein on hemodynamics in the stage-17
chick embryo. 32 chick embryos HH 17 were subdivided into venous clipped
(N=16) and matched control embryos (N=16). Dorsal aortic blood flow
velocity was measured with a 20 MHz pulsed Doppler meter. A time series of
eight successive measurements per embryo was made starting just before
clipping and ending 5h after clipping. Heart rate, peak systolic velocity,
time-averaged velocity, peak blood flow, mean blood flow, peak
acceleration and stroke volume were determined. All hemodynamic parameters
decreased acutely after venous clipping and only three out of seven
parameters (heart rate, time-averaged velocity and mean blood flow) showed
a recovery to baseline values during the 5h study period. We conclude that
the experimental alteration of venous return has major acute effects on
hemodynamics in the chick embryo. These effects may be responsible for the
observed cardiac malformations after clipping
Ventricular diastolic filling characteristics in stage-24 chick embryos after extra-embryonic venous obstruction
Alteration of extra-embryonic venous blood flow in stage-17 chick embryos
results in well-defined cardiovascular malformations. We hypothesize that
the decreased dorsal aortic blood volume flow observed after venous
obstruction results in altered ventricular diastolic function in stage-24
chick embryos. A microclip was placed at the right lateral vitelline vein
in a stage-17 (52-64 h of incubation) chick embryo. At stage 24 (4.5 days
of incubation), we measured simultaneously dorsal aortic and
atrioventricular blood flow velocities with a 20-MHz pulsed-Doppler
velocity meter. The fraction of passive and active filling was integrated
and multiplied by dorsal aortic blood flow to obtain the relative passive
and active ventricular filling volumes. Data were summarized as means +/-
S.E.M. and analyzed by t-test. At similar cycle lengths ranging from 557
ms to 635 ms (P>0.60), dorsal aortic blood flow and stroke volume measured
in the dorsal aorta were similar in stage-24 clipped and normal embryos.
Passive filling volume (0.07+/-0.01 mm(3)) was decreased, and active
filling volume (0.40+/-0.02 mm(3)) was increased in the clipped embryo
when compared with the normal embryo (0.15+/-0.01 mm(3), 0.30+/-0.01
mm(3), respectively) (P<0.003). In the clipped embryos, the passive/active
ratio was decreased compared with that in normal embryos (P<0.001).
Ventricular filling components changed after partially obstructing the
extra-embryonic venous circulation. These results suggest that material
properties of the embryonic ventricle are modified after temporarily
reduced hemodynamic load