Comparison between Alpha-1 Adrenoceptor-Mediated and Beta Adrenoceptor-Mediated Inotropic Components Elicited by Norepinephrine in Failing Human Ventricular Muscle 1

ABSTRACT The purpose of our study was to investigate the inotropic response to the endogenous agonist norepinephrine mediated through alpha-1 adrenoceptors and to compare this response to that mediated through beta-adrenoceptors in failing human ventricular myocardium. We studied ex vivo the inotropic effect of norepinephrine in isometrically contracting trabecular myocardium from both ventricles of explanted hearts. By studying influence of appropriate adrenoceptor blockers, qualitative characteristics of the inotropic response and sensitivity of the inotropic response to cholinergic stimulation, it was revealed that norepinephrine evoked both alpha-1 and beta adrenoceptor-mediated inotropic effects in failing human ventricle myocardium. Quantitatively the inotropic responses to norepinephrine varied markedly between preparations, but the mean responses elicited through the respective adrenoceptor systems were of comparable magnitude. Concomitant stimulation of alpha-1 and beta adrenoceptors by norepinephrine alone revealed a contribution of an alpha-1 adrenoceptor-mediated component to the final and unopposed inotropic response. Differential sensitivity of the two adrenoceptor systems to norepinephrine depending on etiology of heart failure and possibly also thyroid status was observed. It is concluded that norepinephrine evokes an alpha-1 adrenoceptor-mediated inotropic effect comparable to that evoked through the beta adrenoceptors in failing human ventricular myocardium, and that this alpha-1 adrenoceptor-mediated inotropic effect may be of functional importance. The catecholamine-induced increase in contractile force in mammalian myocardium is mainly due to activation of beta adrenoceptors. The existence of myocardial alpha-1 adrenoceptors mediating positive inotropic effects is, however, now well established In the failing human heart where the beta-1 adrenoceptor mediated inotropic response is attenuated, it has been difficult to demonstrate an alpha-1 adrenoceptor-mediated inotropic effect of functional significance (e.g.

Placental volume in gestational week 27 measured by three dimensional ultrasound and magnetic resonance imaging

Introduction Ultrasound is the diagnostic tool of choice in pregnancy. We lack valid ultrasound methods for placental size measurements. Our aim was therefore to compare three-dimensional (3D) ultrasound with magnetic resonance imaging (MRI) for measurements of placental volume. Material and methods We measured placental volume by 3D ultrasound and MRI in 100 unselected pregnancies at 27 weeks of gestation (25+4–28+4 weeks). The 3D ultrasound acquisitions were analyzed offline, and the placental outline was manually traced using the virtual organ computer-aided analysis (VOCAL) 30° rotational technique. The MRI examinations included a T2-weighted gradient echo sequence in the sagittal plane, with 5-mm slices through the entire uterus. The placental outline was manually traced in each slice. The correlation between 3D ultrasound and MRI placental volumes was estimated by intraclass correlation coefficients. Bland-Altman analysis was applied to visualize systematic bias and limits of agreement, in which the ratio MRI placental volume/3D ultrasound placental volume was plotted against the average of the two methods. Results The intraclass correlation coefficient between 3D ultrasound and MRI measurements was 0.49 (95% confidence interval 0.33-0.63). In general, 3D ultrasound measured smaller placental volumes (median 373 cm3, interquartile range 309-434 cm3) than MRI (median 507 cm3, interquartile range 429-595 cm3) and the systematic bias was 1.44. The 95% limits of agreement between the two methods were wide (0.68-2.21). Conclusions We found poor to moderate correlation between 3D ultrasound and MRI placental volume measurements. Generally, 3D ultrasound measured smaller placental volumes than MRI, suggesting that 3D ultrasound failed to visualize the entire placenta. Our findings may hopefully contribute to the improvement of ultrasound methods for placental measurements