Pulmonary hypertension in sickle-cell disease: comorbidities and echocardiographic findings.
ABSTRACT Our aim is to determine comorbidities associated with pulmonary hypertension (PHT) in clinically stable sickle-cell disease (SCD) patients and to evaluate left ventricular (LV) and right ventricular (RV) function in those patients.
Echocardiography was performed in 87 SCD patients that were divided into group I (without PHT) and group II (with PHT). Both groups were compared with healthy controls.
A history of retinopathy and leg ulcer was more frequent in group II than group I (p < 0.01). Haemoglobin levels were lower (p < 0.05), whereas blood urea nitrogen, lactate dehydrogenase and total bilirubin levels were higher in group II (p < 0.01). Although group II patients had larger LV end-diastolic, LV end-systolic and RV diastolic diameters compared with group I patients and controls (p < 0.05), LV ejection fraction was similar in the three groups. The mitral peak early diastolic inflow velocity to peak late diastolic inflow velocity (E/A) ratio was similar in group I, group II and the control group. The tricuspid E/A ratio was lower in group II than group I and controls (p < 0.05).
End organ damage occurs more often and haemolysis is severer in SCD patients with PHT than SCD patients without PHT. Although LV systolic and diastolic function is well preserved, RV diastolic function is disturbed in those patients with PHT.
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ABSTRACT: Raised tricuspid regurgitant velocity (TRV) occurs in approximately 30% of adults with sickle cell disease (SCD), and has been shown to be an independent risk factor for death. TRV was assessed in 164 SCD patients who were subsequently followed up for survival. Raised pulmonary pressures were defined as a TRV jet ≥2·5 m/s on echocardiography. Elevated TRV was present in 29·1% of patients and it was associated with increased age and left atrial diameter. There were 15 deaths (9·1%) over a median of 68·1 months follow up; seven patients had increased TRV, and eight patients had a TRV<2·5 m/s. Higher TRV values were associated with a greater than 4-fold increased risk of death (Hazard Ratio: 4·48, 99% confidence interval 1·01-19·8), although we found a lower overall mortality rate than has been reported in previous studies. TRV was not an independent risk factor for death. We have confirmed the association between raised TRV and mortality in a UK SCD population whose disease severity appears to be less than that reported in previous studies. Further prospective studies are needed to more clearly characterize which patient factors modify survival in SCD patients with raised TRV.British Journal of Haematology 05/2013; 162(3). DOI:10.1111/bjh.12391 · 4.96 Impact Factor
Conference Paper: Computational intelligence and cerebellar enigmas[Show abstract] [Hide abstract]
ABSTRACT: A three-layer cerebellar cortex presents a kind of ideal network for early perceptron theories, but its functioning is much more complicated. Three related topics connected with information coding and memorizing mechanisms in the cerebellum are considered: 1) demonstration that activity transformation by granule cells, conserves the signal continuity provided by snake-in-box type codes; 2) determining precision requirements for the standard CMAC as well as for more realistic cerebellar models to meet demands of adaptive critic based solutions for a nonlinear control problem (swinging pendulum); and 3) demonstration that the closed loop scheme for the synaptic weight adjustment provides a precise setting of cerebellar input-output relations and multiple predictions for physiological experimentsNeural Networks Proceedings, 1998. IEEE World Congress on Computational Intelligence. The 1998 IEEE International Joint Conference on; 06/1998
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ABSTRACT: Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by microvascular vaso-occlusion with erythrocytes containing polymerized sickle (S) hemoglobin, erythrocyte hemolysis, vasculopathy, and both acute and chronic multiorgan injury. It is associated with steady state increases in plasma cell-free hemoglobin and overproduction of reactive oxygen species (ROS). Hereditary and acquired hemolytic conditions release into plasma hemoglobin and other erythrocyte components that scavenge endothelium-derived NO and metabolize its precursor arginine, impairing NO homeostasis. Overproduction of ROS, such as superoxide, by enzymatic (xanthine oxidase, NADPH oxidase, uncoupled eNOS) and nonenzymatic pathways (Fenton chemistry), promotes intravascular oxidant stress that can likewise disrupt NO homeostasis. The synergistic bioinactivation of NO by dioxygenation and oxidation reactions with cell-free plasma hemoglobin and ROS, respectively, is discussed as a mechanism for NO resistance in SCD vasculopathy. Human physiological and transgenic animal studies provide experimental evidence of cardiovascular and pulmonary resistance to NO donors and reduced NO bioavailability that is associated with vasoconstriction, decreased blood flow, platelet activation, increased endothelin-1 expression, and end-organ injury. Emerging epidemiological data now suggest that chronic intravascular hemolysis is associated with certain clinical complications: pulmonary hypertension, cutaneous leg ulcerations, priapism, and possibly stroke. New therapeutic strategies to limit intravascular hemolysis and ROS generation and increase NO bioavailability are discussed.Free Radical Biology and Medicine 05/2008; 44(8):1506-28. DOI:10.1016/j.freeradbiomed.2008.01.008 · 5.71 Impact Factor