The Effect of Cardiac Cycle Length on Ventricular End-Diastolic Pressure and Maximum Time Derivative of Pressure in the Stage 24 Chick Embryo

Abstract

ABSTRACT. We hypothesized that developmental in-(1) have shown that increases in both ventricular EDP and creases in both ventricular end-diastolic pressure (EDP) maximum dP/dt occur concurrently with CL decrease (heart and the maximum time derivative of pressure (dP/dt) ob-rate increase) from d 2 to 6 (Hamburger-Hamilton stages 12 to served in stage 12 to 29 chick embryos are the result of 29) of a 21-d incubation. observed cardiac cycle length (CL) decrease (heart rateWe wondered to what extent the developmental changes in increase). To test this hypothesis, we evaluated EDP and EDP and dP/dt might reflect observed changes in CL. The dP/dt changes that occur during acute CL alterations in purpose of this study, therefore, is to examine whether the the Hamburger-Hamilton stage 24 chick embryo (n = 18). observed increases in both EDP and dP/dt are a function of the Ventricular pressure measurements were obtained with a observed decrease in CL. We evaluated EDP and maximum dP/ servo-null pressure system and digitally recorded at 500 dt during acute CL alterations in the stage 24 (d 4) chick embryo. samples/s. A 1-mm steel probe, heated (decrease CL) or By studying these relationships in a single stage of development, cooled (increase CL), was applied to the sinus venosus. the effect of CL alteration can be assessed independently of other The average baseline CL was 454 ms. The heart rate effects secondary to changes in cardiac morphology. perturbation resulted in CL that varied over a range of 200-2966 ms, assimilating the range of CL change observed during development. Changes in EDP ranged from 0.014 to 0.130 kPa (baseline = 0.061 kPa) and maximum MATERIALS AND METHODS dP/dt ranged from 0.33 to 13.33 kPa/s (baseline = 5.99) Fertile White Leghorn chicken eggs were incubated to HamkPa/s). In each study, EDP varied directly with CL (R2 = burger-Hamilton stage 24 (4 d) at 38°C (2). An egg was removed 0.70). Conversely, maximum dP/dt changes were inversely from the incubator and placed in a heated sand bath (Bioengirelated to CL alterations (R2 = 0.54). Thus, we found that neering Department, Medical College of Georgia) under a radiant there is a direct relationship between changes in CL and warmer to maintain a constant egg temperature of 37-38°C EDP in the stage 24 chick embryo, whereas CL and dP/dt throughout the experiment. The embryo was exposed by removvary inversely. During cardiac development, observed in-ing a portion of the shell and the overlying membranes. The CL creases in maximum dP/dt may be attributed to CL de-was altered using a 1-mm stainless steel probe that was first creases. In contrast, developmental increases in EDP can-heated or cooled in a water bath. The probe was then placed on not be explained by CL decrease and must be accounted the sinus venosus for 10 s to shorten or lengthen the CL. An for by maturational changes in cardiac function in the chick additional 10 control studies were performed using a probe at embryo. (Pediatr Res 29: 338-341, 1991) 37-38°C to exclude pressure of the pr...

Validating the Paradigm That Biomechanical Forces Regulate Embryonic Cardiovascular Morphogenesis and Are Fundamental in the Etiology of Congenital Heart Disease

“…Early stage embryos displayed ventricular filling velocities consistent with a relatively non-compliant chamber with increasing passive filling during ventricular expansion [ 56 ]. Acute changes in heart rate produce inverse changes in ventricular pressure and SV ( Figure 5 ) [ 21 , 101 ], though dorsal aortic blood flow is maximal at intrinsic heart rates [ 102 , 103 ]. PV analysis showed that isovolumic contraction time remained independent of cycle length, while ventricular end-diastolic filling times, end diastolic volumes, and SV varied linearly with cycle length [ 104 ].…”