PubMed · 7363790
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F W Rieben. 1980-03-28. [Miction syncope].. https://doi.org/10.1055/s-2008-1070680
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BACKGROUND: By using Doppler echocardiography, we determined the normal distribution of human fetal combined cardiac output (CCO) from the left and right ventricles. We also established weight-indexed pulmonary and systemic vascular resistances (Rpi and Rsi, respectively) and changes during the second half of pregnancy. METHODS AND RESULTS: Blood flows at the aortic and pulmonary valve annuli (LVCO and RVCO, respectively), right and left pulmonary arteries (QP), and ductus arteriosus (QDA) were calculated in 63 normal fetuses. Foramen ovale blood flow (QFO = LVCO-QP) was estimated. From 20 to 30 weeks of gestation, the proportion of QP of the CCO increased (from 13% to 25%, P < .001), while the proportion of QFO decreased (from 34% to 18%, P < .001). After 30 weeks, the proportions of QP and QFO were unchanged. At 38 weeks, the proportion of RVCO (60%) was higher (P < .05) than that of LVCO (40%). The proportion of QDA did not change significantly. The correlation between RVCO calculated from blood flow through the pulmonary valve and from QDA and QP was good (r = .97, P < .0001). RPi (P < .001) decreased from 20 to 30 weeks of gestation. From 30 to 38 weeks, RPi increased (P < .0001). Rsi increased (P < .001) from 20 to 38 weeks. The ratio of RPi to RSi decreased (P < .01) from 20 to 30 weeks and later remained unchanged. CONCLUSIONS: The human fetal pulmonary circulation has an important role in the distribution of cardiac output.
BACKGROUND: Three-dimensional echocardiography can allow us to address uniquely three-dimensional scientific questions, for example, the hypothesis that the impact of a stenotic valve depends not only on its limiting orifice area but also on its three-dimensional geometry proximal to the orifice. This can affect the coefficient of orifice contraction (Cc = effective/anatomic area), which is important because for a given flow rate and anatomic area, a lower Cc gives a higher velocity and pressure gradient, and Cc, routinely assumed constant in the Gorlin equation, may vary with valve shape (60% for a flat plate, 100% for a tube). To date, it has not been possible to study this with actual valve shapes in patients. METHODS AND RESULTS: Three-dimensional echocardiography reconstructed valve geometries typical of the spectrum in patients with mitral stenosis: mobile doming, intermediate conical, and relatively flat immobile valves. Each geometry was constructed with orifice areas of 0.5, 1.0 and 1.5 cm2 by stereolithography (computerized laser polymerization) (total, nine valves) and studied at physiological flow rates. Cc varied prominently with shape and was larger for the longer, tapered dome (more gradual flow convergence proximal and distal to the limiting orifice): for an anatomic orifice of 1.5 cm2, Cc increased from 0.73 (flat) to 0.87 (dome), and for an area of 0.5 cm2, from 0.62 to 0.75. For each shape, Cc increased with increasing orifice size relative to the proximal funnel (more tubelike). These variations translated into important differences of up to 40% in pressure gradient for the same anatomic area and flow rate (greatest for the flattest valves), with a corresponding variation in calculated Gorlin area (an effective area) relative to anatomic values. CONCLUSIONS: The coefficient of contraction and the related net pressure loss are importantly affected by the variations in leaflet geometry seen in patients with mitral stenosis. Three-dimensional echocardiography and stereolithography, with the use of actual information from patients, can address such uniquely three-dimensional questions to provide insight into the relations between cardiac structure, pressure, and flows.
To determine the independent prognostic significance of left ventricular (LV) mass and geometry (concentric vs eccentric pattern) in hypertensive subjects with LV hypertrophy at echocardiography, 274 subjects were followed for up to 8.7 years (mean 3.2). All patients had systemic hypertension and LV mass > or = 125 g/body surface area (BSA) and underwent ambulatory blood pressure (BP) monitoring and echocardiography before treatment. Eccentric and concentric hypertrophy were defined by the ratio between LV posterior wall thickness and LV radius at telediastole <0.45 and > or = 0.45, respectively. Age, sex ratio, body mass index, office BP and serum glucose, cholesterol, and triglycerides did not differ between the groups with eccentric (n=145) and concentric (n=129) hypertrophy. Average 24-hour daytime, and nighttime systolic ambulatory BPs were higher in concentric than in eccentric hypertrophy (all p <0.01). LV mass was slightly greater in concentric than in eccentric hypertrophy (157 vs 149 g/BSA, p <0.05). Endocardial and midwall shortening fraction were lower in concentric than in eccentric hypertrophy (96.5% vs 106.0% of predicted and 71.4% vs 89.7% of predicted, respectively; both p <0.01). The rate of major cardiovascular morbid events was 2.20 and 3.34 per 100 patient-years in eccentric and concentric hypertrophy, respectively (log rank test, p=NS). Age >60 and LV mass above median (145 g/BSA) were significant adverse prognostic predictors, while LV geometry (eccentric vs concentric hypertrophy) and ambulatory BP were not. The event rates per 100 patient-years were 1.38 and 3.98, respectively, in the patients with LV mass below and above median (age-adjusted relative risk 2.70; 95% confidence interval [CI] 1.03 to 6.63; p=0.015). In hypertensive subjects with established LV hypertrophy, LV mass, but not its geometric pattern, provides important prognostic information independent of conventional risk markers including office and ambulatory BP.