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This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below -11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.
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HERAS is a tool developed in Matlab for the analysis of reflector antennas using physical optics (PO) theory. Its graphical user interface (GUI) and source code are freely available for educational and research purposes. It has the necessity of being a flexible tool to provide adaptability to system engineering requirements and can also be of interest to antenna engineers working on the design of reflector antennas. Due to the increasing demand of broadband services, satellite communications systems are becoming highly complex in order to meet connectivity requirements. To fully exploit the benefits of these systems, multidimensional optimisations are crucial, which call for an efficient estimation of the coverage characteristics. Reflector-based solutions are one of the preferred architectures for very high-throughput satellite (VHTS) systems. A detailed description of HERAS is presented in this paper which has been validated with available commercial software packages. In addition, some examples are described in which the tool has been used for the efficient estimation of VHTS systems performance.
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A very compact waveguide orthomode transducer (OMT) is described in this paper. The design is characterized with a twofold rotationally symmetric cross-section in the probing area, adapted from a side-coupling OMT design, simultaneously enabling low port-to-port coupling and high cross-polarization discrimination (XPD) over a fractional bandwidth of about 15-20%. Compared to previously reported compact waveguide OMTs, the proposed design is simpler, thus facilitating its manufacture at millimeter-wave frequencies. The concept is demonstrated with a design in the K-band for a broadband communication satellite downlink over the frequency band of 17.3-20.2 GHz. For test purposes, transitions to standard waveguide WR42 are included, and the OMT is assembled with a conical horn antenna. The measured reflection and coupling coefficients are below -19.5 dB and -22.9 dB, respectively, over the nominal bandwidth, and they are in good agreement with the simulation's results. The on-axis XPD, measured in an anechoic chamber, is better than 30 dB over the nominal bandwidth, which is also in line with simulations. The proposed waveguide OMT may be designed to fit in a lattice below one wavelength at the highest operating frequency, which is desirable for dual-polarized closely spaced array antennas in low and medium Earth orbit communication satellite systems. The simple mechanical design of the proposed OMT makes it particularly appealing for additive manufacturing techniques, as demonstrated with a variant of the design having folded single-mode waveguides, which preserves the RF properties of the original design.
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Comercio , Refracción Ocular , Comunicaciones por Satélite , TransductoresRESUMEN
Electromagnetic linear-to-circular polarization converters with wide- and multi-band capabilities can simplify antenna systems where circular polarization is required. Multi-band solutions are attractive in satellite communication systems, which commonly have the additional requirement that the sense of polarization is reversed between adjacent bands. However, the design of these structures using conventional ad hoc methods relies heavily on empirical methods. Here, we employ a data-driven approach integrated with a generative adversarial network to explore the design space of the polarizer meta-atom thoroughly. Dual-band and triple-band reflective polarizers with stable performance over incident angles up to and including 30°, corresponding to typical reflector antenna system requirements, are synthesized using the proposed method. The feasibility and performance of the designed polarizer is validated through measurements of a fabricated prototype.
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A review of technological solutions and advances in the framework of a Vertical Heterogeneous Network (VHetNet) integrating satellite, airborne and terrestrial networks is presented. The disruptive features and challenges offered by a fruitful cooperation among these segments within a ubiquitous and seamless wireless connectivity are described. The available technologies and the key research directions for achieving global wireless coverage by considering all these layers are thoroughly discussed. Emphasis is placed on the available antenna systems in satellite, airborne and ground layers by highlighting strengths and weakness and by providing some interesting trends in research. A summary of the most suitable applicative scenarios for future 6G wireless communications are finally illustrated.
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Tecnología , Tecnología InalámbricaRESUMEN
A double-layer lens consists of a first gradient-index/geodesic profile in an upper waveguide, partially surrounded by a mirror that reflects the wave into a lower guide where there is a second profile. Here, we derive a new family of rotational-symmetric inhomogeneous index profiles and equivalent geodesic lens shapes by solving an inverse problem of pre-specified focal points. We find an equivalence where single-layer lenses have a different functionality as double-layer lenses with the same profiles. As an example, we propose, manufacture, and experimentally validate a practical implementation of a geodesic double-layer lens that is engineered for a low-profile antenna with a compact footprint in the millimeter wave band. Its unique double-layer configuration allows for two-dimensional beam scanning using the same footprint as an extension of the presented design. These lenses may find applications in future wireless communication systems and sensing instruments in microwave, sub-terahertz, and optical domains.
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The paper proposes a new set of normalization techniques for precoding/beamforming matrices applicable to broadband multiuser multiple-input multiple-output (MIMO) satellite systems. The proposed techniques adapt known normalization methods to account for the signal attenuation experienced by users due to the degradation of antenna gain and free space losses towards the edge of the coverage. We use, as an example, an array-fed reflector (AFR) antenna onboard a satellite in geosynchronous orbit (GEO), which provides a favorable trade-off between high-directivity, reconfigurability, and the requirement for digital processing, but suffers from high scan losses away from broadside due to optical aberrations when considered for global coverage applications. Three different precoding/beamforming techniques are employed, namely zero forcing (ZF), minimum mean squared error (MMSE), and matched filtering (MF). Low-complexity power normalization techniques digitally applied after the beamformer are introduced that, in the absence of any atmospheric effects, lead to iso-flux-like characteristics whilst satisfying the power constraint per feed. In comparison with other methods reported in the literature, mainly based on iterative algorithms, the proposed techniques consist in closed-form expressions to provide uniform signal-to-noise ratio (SNR) and signal-to-noise plus interference ratio (SNIR) across the users without significant impact on the payload sum rate. Numerical results are presented to comparatively demonstrate the achieved performance in terms of total capacity and distribution of SNR and SNIR at various noise and interference scenarios.
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Phosphatidylinositol 3-kinase (PI3K) activation is necessary for insulin-responsive glucose transporter (GLUT4) translocation and glucose transport. Insulin and platelet-derived growth factor (PDGF) stimulate PI3K activity in 3T3-L1 adipocytes, but only insulin is capable of stimulating GLUT4 translocation and glucose transport. We found that PDGF causes serine/threonine phosphorylation of insulin receptor substrate 1 (IRS-1) in 3T3-L1 cells, measured by altered mobility on SDS-polyacrylamide gel, and this leads to a decrease in insulin-stimulated tyrosine phosphorylation of IRS-1. The PI3K inhibitors wortmannin and LY294002 inhibit the PDGF-induced phosphorylation of IRS-1, whereas the MEK inhibitor PD98059 was without a major effect. PDGF pretreatment for 60-90 min led to a marked 80-90% reduction in insulin stimulatable phosphotyrosine and IRS-1-associated PI3K activity. We examined the functional consequences of this decrease in IRS-1-associated PI3K activity. Interestingly, insulin stimulation of GLUT4 translocation and glucose transport was unaffected by 60-90 min of PDGF preincubation. Furthermore, insulin activation of Akt and p70(s6kinase), kinases downstream of PI3K, was unaffected by PDGF pretreatment. Wortmannin was capable of blocking these insulin actions following PDGF pretreatment, suggesting that PI3K was still necessary for these effects. In conclusion, 1) PDGF causes serine/threonine phosphorylation of IRS-1, and PI3K, or a kinase downstream of PI3K, mediates this phosphorylation. 2) This PDGF-induced phosphorylation of IRS-1 leads to a significant decrease in insulin-stimulated PI3K activity. 3) PDGF has no effect on insulin stimulation of Akt, p70(s6kinase), GLUT4 translocation, or glucose transport. 4) This suggests the existence of an IRS-1-independent pathway leading to the activation of PI3K, Akt, and p70(s6kinase); GLUT4 translocation; and glucose transport.
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Glucosa/metabolismo , Antagonistas de Insulina/farmacología , Proteínas Musculares , Fosfatidilinositol 3-Quinasas/metabolismo , Fosfoproteínas/metabolismo , Factor de Crecimiento Derivado de Plaquetas/farmacología , Células 3T3 , Adipocitos/efectos de los fármacos , Adipocitos/enzimología , Animales , Transporte Biológico , Activación Enzimática , Transportador de Glucosa de Tipo 4 , Insulina/farmacología , Proteínas Sustrato del Receptor de Insulina , Ratones , Proteínas de Transporte de Monosacáridos/metabolismo , Fosforilación , Serina/metabolismo , Treonina/metabolismo , Tirosina/metabolismoRESUMEN
Phospholipase C-gamma (PLCgamma) is the isozyme of PLC phosphorylated by multiple tyrosine kinases including epidermal growth factor, platelet-derived growth factor, nerve growth factor receptors, and nonreceptor tyrosine kinases. In this paper, we present evidence for the association of the insulin receptor (IR) with PLCgamma. Precipitation of the IR with glutathione S-transferase fusion proteins derived from PLCgamma and coimmunoprecipitation of the IR and PLCgamma were observed in 3T3-L1 adipocytes. To determine the functional significance of the interaction of PLCgamma and the IR, we used a specific inhibitor of PLC, U73122, or microinjection of SH2 domain glutathione S-transferase fusion proteins derived from PLCgamma to block insulin-stimulated GLUT4 translocation. We demonstrate inhibition of 2-deoxyglucose uptake in isolated primary rat adipocytes and 3T3-L1 adipocytes pretreated with U73122. Antilipolytic effect of insulin in 3T3-L1 adipocytes is unaffected by U73122. U73122 selectively inhibits mitogen-activated protein kinase, leaving the Akt and p70 S6 kinase pathways unperturbed. We conclude that PLCgamma is an active participant in metabolic and perhaps mitogenic signaling by the insulin receptor in 3T3-L1 adipocytes.
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Adipocitos/metabolismo , Insulina/metabolismo , Isoenzimas/metabolismo , Proteínas Musculares , Receptor de Insulina/metabolismo , Transducción de Señal , Fosfolipasas de Tipo C/metabolismo , Células 3T3 , Adipocitos/enzimología , Animales , Desoxiglucosa/metabolismo , Inhibidores Enzimáticos/farmacología , Estrenos/farmacología , Transportador de Glucosa de Tipo 4 , Isoenzimas/antagonistas & inhibidores , Lipólisis , Masculino , Ratones , Microinyecciones , Proteínas de Transporte de Monosacáridos/metabolismo , Fosfolipasa C gamma , Pirrolidinonas/farmacología , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes de Fusión/metabolismo , Fosfolipasas de Tipo C/antagonistas & inhibidores , Dominios Homologos srcRESUMEN
To delineate the signaling pathway leading to glucose transport protein (GLUT4) translocation, we examined the effect of microinjection of the nonhydrolyzable GTP analog, guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS), into 3T3-L1 adipocytes. Thirty minutes after the injection of 5 mM GTPgammaS, 40% of injected cells displayed surface GLUT4 staining indicative of GLUT4 translocation compared with 55% for insulin-treated cells and 10% in control IgG-injected cells. Treatment of the cells with the phosphatidylinositol 3-kinase inhibitor wortmannin or coinjection of GST-p85 SH2 fusion protein had no effect on GTPgammaS-mediated GLUT4 translocation. On the other hand, coinjection of antiphosphotyrosine antibodies (PY20) blocked GTPgammaS-induced GLUT4 translocation by 65%. Furthermore, microinjection of GTPgammaS led to the appearance of tyrosine-phosphorylated proteins around the periphery of the plasma membrane, as observed by immunostaining with PY20. Treatment of the cells with insulin caused a similar phosphotyrosine-staining pattern. Electroporation of GTPgammaS stimulated 2-deoxy-D-glucose transport to 70% of the extent of insulin stimulation. In addition, immunoblotting with phosphotyrosine antibodies after electroporation of GTPgammaS revealed increased tyrosine phosphorylation of several proteins, including 70- to 80-kDa and 120- to 130-kDa species. These results suggest that GTPgammaS acts upon a signaling pathway either downstream of or parallel to activation of phosphatidylinositol 3-kinase and that this pathway involves tyrosine-phosphorylated protein(s).
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Guanosina 5'-O-(3-Tiotrifosfato)/farmacología , Proteínas de Transporte de Monosacáridos/metabolismo , Proteínas Musculares , Tirosina/metabolismo , Células 3T3 , Adipocitos/metabolismo , Animales , Transporte Biológico/efectos de los fármacos , Electroporación , Transportador de Glucosa de Tipo 4 , Ratones , Microinyecciones , Peso Molecular , Fosfatidilinositol 3-Quinasas/fisiología , FosforilaciónRESUMEN
Insulin's stimulation of glucose transport involves the translocation of vesicles containing the glucose transporter GLUT4 to the plasma membrane. Small GTP-binding proteins have been implicated in the regulation of vesicular traffic. We studied the effects of microinjection of wild-type Rab4 glutathione S-transferase fusion protein (WT Rab4), a GTP-binding defective mutant (Rab4 N121I), a guanosine triphosphatase-defective mutant (Rab4 Q67L), and a Rab4 antibody on insulin-induced GLUT4 translocation in 3T3-L1 adipocytes. Microinjection of Rab4 N121I and Rab4 antibodies had no effect on basal GLUT4 staining, but inhibited insulin-induced GLUT4 translocation by 50% compared with that in control IgG-injected cells. WT Rab4 and Rab4 Q67L microinjection had no effect on either basal or insulin-induced GLUT4 translocation. Premixing and coinjection of the Rab4 antibody with WT Rab4 almost completely abolished its inhibitory effect on insulin-induced GLUT4 translocation. In contrast, microinjection of an antibody directed against the highly conserved region of Rab3 proteins had no effect on insulin-induced GLUT4. These results point to a direct role of Rab4 in insulin-induced GLUT4 translocation, and that this effect is dependent on nucleotide binding to the protein. We also studied the effect of microinjection of the same proteins on insulin-induced actin filament rearrangement (membrane ruffling) in the same cell line. Microinjection of Rab4 N121I and Rab4 antibodies inhibited insulin-induced membrane ruffling by 40%, whereas WT Rab4 or a Rab3 antibody injection had no effect on cytoskeletal rearrangement. In summary, 1) Rab4 is a necessary component of the insulin/GLUT4 translocation signaling pathway; 2) the function of Rab4 in this pathway requires GTP binding; 3) Rab4 also participates in the process of insulin-induced membrane ruffling; and 4) Rab3 proteins do not seem to be involved in these processes.
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Actinas/fisiología , Adipocitos/fisiología , Proteínas de Unión al GTP/fisiología , Insulina/farmacología , Proteínas de Transporte de Monosacáridos/metabolismo , Proteínas Musculares , Células 3T3 , Adipocitos/metabolismo , Animales , Anticuerpos/inmunología , Anticuerpos/farmacología , Transporte Biológico/efectos de los fármacos , Transporte Biológico/fisiología , Western Blotting , GTP Fosfohidrolasas/genética , GTP Fosfohidrolasas/farmacología , Proteínas de Unión al GTP/genética , Proteínas de Unión al GTP/inmunología , Transportador de Glucosa de Tipo 4 , Glutatión Transferasa/farmacología , Ratones , Microinyecciones , Mutación , Proteínas de Unión al GTP rab3 , Proteínas de Unión al GTP rab4RESUMEN
Interaction of the activated insulin receptor (IR) with its substrate, insulin receptor substrate 1 (IRS-1), via the phosphotyrosine binding domain of IRS-1 and the NPXY motif centered at phosphotyrosine 960 of the IR, is important for IRS-1 phosphorylation. We investigated the role of this interaction in the insulin signaling pathway that stimulates glucose transport. Utilizing microinjection of competitive inhibitory reagents in 3T3-L1 adipocytes, we have found that disruption of the IR/IRS-1 interaction has no effect upon translocation of the insulin-responsive glucose transporter (GLUT4). The activity of these reagents was demonstrated by their ability to block insulin stimulation of two distinct insulin bioeffects, membrane ruffling and mitogenesis, in 3T3-L1 adipocytes and insulin-responsive rat 1 fibroblasts. These data suggest that phosphorylated IRS-1 is not an essential component of the metabolic insulin signaling pathway that leads to GLUT4 translocation, yet it appears to be required for other insulin bioeffects.
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Insulina/fisiología , Proteínas de Transporte de Monosacáridos/metabolismo , Proteínas Musculares , Fosfoproteínas/metabolismo , Células 3T3 , Adipocitos/metabolismo , Secuencia de Aminoácidos , Animales , Compartimento Celular , Membrana Celular/ultraestructura , Transportador de Glucosa de Tipo 4 , Proteínas Sustrato del Receptor de Insulina , Ratones , Microscopía Fluorescente , Mitosis , Datos de Secuencia Molecular , Oligopéptidos/química , Ratas , Transducción de SeñalRESUMEN
Insulin stimulates glucose transport largely by mediating translocation of the insulin-sensitive glucose transporter (GLUT4) from an intracellular compartment to the plasma membrane. Using single cell microinjection of 3T3-L1 adipocytes, coupled with immunofluorescence detection of GLUT4 proteins, we have determined that inhibition of endogenous p21ras or injection of oncogenic p21ras has no effect on insulin-stimulated GLUT4 translocation. On the other hand, microinjection of anti-phosphotyrosine antibodies or inhibition of endogenous phosphatidylinositol 3-kinase by microinjection of a GST-p85 SH2 fusion protein markedly inhibits this biologic effect of insulin. These data suggest that the p21ras/mitogen-activated protein kinase pathway is not involved in this metabolic effect of insulin, whereas tyrosine phosphorylation and stimulation of phosphatidylinositol 3-kinase activity are critical components of this signaling pathway.
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Adipocitos/metabolismo , Insulina/farmacología , Proteínas de Transporte de Monosacáridos/metabolismo , Proteínas Musculares , Receptor de Insulina/fisiología , Transducción de Señal , 1-Metil-3-Isobutilxantina/farmacología , Células 3T3 , Adipocitos/citología , Adipocitos/efectos de los fármacos , Animales , Diferenciación Celular , Línea Celular , Membrana Celular/metabolismo , Dexametasona/farmacología , Fibroblastos , Genes ras , Transportador de Glucosa de Tipo 4 , Humanos , Cinética , Ratones , Proteínas Proto-Oncogénicas p21(ras)/biosíntesis , Proteínas Proto-Oncogénicas p21(ras)/metabolismo , Ratas , Receptor de Insulina/biosíntesis , Receptor de Insulina/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Porcinos , TransfecciónRESUMEN
A Podospora anserina longevity mutant was identified with a temperature-sensitive phenotype for senescence. This mutant, termed TS1, grew for over 3 m at 27 degrees C, but when shifted to 34 degrees C, it underwent senescence between 10 and 18 cm. A previously described senescence-associated plasmid, alpha senDNA, derived from the mitochondrial genome, was not detected in TS1 at 27 degrees C but was present in senescent cultures at 34 degrees C. A similar result was observed in progeny strains obtained by crossing the TS1 mutant with a wild-type strain. Other mitochondrial excision-amplification DNAs in addition to alpha senDNA were also observed in the senescent cultures. Most were derived from a specific region of the mitochondrial genome. These results provide evidence that alpha senDNA is involved in TS1 senescence and suggest that this plasmid may play a role in the formation of other mitochondrial excision-amplification plasmids.
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Envejecimiento , Ascomicetos/genética , ADN Mitocondrial/genética , Plásmidos , Ascomicetos/crecimiento & desarrollo , ADN de Hongos/genética , Amplificación de Genes , Genes Fúngicos , Mutación , TemperaturaRESUMEN
A hydrostatic theory of blackout is generally supported in the acceleration literature, but there is disagreement as to the correct origin in the thorax for h, the hydrostatic distance to the eye. Our goal was to determine whether representative published data would preferentially support some particular origin for h. Based upon a reanalysis of published data (1) relating acceleration tolerance (T) to seat-back angle (theta), it was found that a simple hydrostatic model, with h measured from the aortic valve to the eye, yields an excellent fit. The nonlinear equation fitted was Ti = Tmin 1/cos(theta i-phi), where phi = correction to back angle. The value of phi derived from the 1975 data (1) (13.74 degrees) was the same as the independent estimate of phi for this same seat (13.06 degrees) derived from published values of h, which were measured by X-ray with h referenced to the aortic-valve and eye (2). The acceleration tolerance data for the other two seats of the 1984 study also strongly supported the model. Future studies should measure h (aortic valve-to-eye), use seat-back angles giving even spacing on a 1/h scale, and analyze data using the required nonlinear methods.
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Aeronaves/instrumentación , Gravitación , Modelos Biológicos , Aceleración , Humanos , Presión Hidrostática , Análisis de RegresiónRESUMEN
Laminar flow through a conduit is equal to the mean velocity times the cross-sectional area of the orifice. Therefore, volume is equal to the time-velocity integral multiplied by the cross-sectional area. In aortic stenosis, flow in the stenotic jet is laminar and the aortic valve area should be equal to the volume of blood ejected through the valve divided by the time-velocity integral of the aortic jet velocity recorded by continuous-wave Doppler echocardiography. To test whether this concept can be used to accurately determine aortic valve area noninvasively by the Doppler method, 39 patients (age 35 to 82 years, mean 63) underwent pulsed Doppler combined with two-dimensional echocardiography for measurement of stroke volume at the aortic, pulmonic, and mitral anulus as well as continuous-wave Doppler recording of the aortic jet. Aortic valve area determined at cardiac catheterization by the Gorlin equation ranged between 0.4 and 2.07 cm2 (mean 0.89 +/- 0.45). Doppler-derived valve area, determined with the stroke volume value from either the aortic, pulmonic, or mitral anulus, correlated well with the area determined at cardiac catheterization (r = .95, .97, and .96, respectively). A simplified method for measuring aortic valve area derived as the cross-sectional area of the aortic anulus times peak velocity just proximal to the aortic valve divided by peak aortic jet velocity correlated well with measurements obtained at cardiac catheterization (r = .94). An excellent separation between critical and noncritical aortic stenosis was seen using either one of the Doppler methods.(ABSTRACT TRUNCATED AT 250 WORDS)
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Estenosis de la Válvula Aórtica/diagnóstico , Ecocardiografía/métodos , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
Two-dimensional echocardiography was used to aid right ventricular endomyocardial biopsy during 163 procedures in 83 patients being evaluated for myocarditis, cardiac transplant rejection, or drug toxicity. Thirty procedures were performed using combined echocardiography and fluoroscopy and 133 using echocardiography alone. For 80 of the 83 patients (96%) the forceps could be adequately visualized entering the right atrium, crossing the tricuspid valve, and advancing to the right ventricular apex and free wall. The catheter could be guided to biopsy the septum and sample multiple, separate sites along the right ventricular walls. By opening the forceps prior to contact with the myocardium, the right ventricular free wall could be biopsied without perforation. We found two-dimensional echocardiography to be a useful and safe technique for forceps visualization and manipulation in the right ventricle.
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Cardiomiopatías/patología , Ecocardiografía/métodos , Antibióticos Antineoplásicos/efectos adversos , Biopsia , Cardiomiopatías/inducido químicamente , Cardiomiopatía Dilatada/patología , Fluoroscopía , Rechazo de Injerto , Trasplante de Corazón , Ventrículos Cardíacos/patología , Humanos , Miocarditis/patología , Miocardio/patología , Naftacenos/efectos adversos , Complicaciones Posoperatorias/patologíaRESUMEN
Fifty-two adults referred for evaluation of aortic stenosis (AS) were studied using continuous-wave and pulsed Doppler echocardiography. Three windows were used to determine which approach (apical, right parasternal or suprasternal) yielded optimal results. Doppler-derived peak aortic valve gradients were compared with the peak gradients measured at cardiac catheterization in 23 patients. High-velocity jets were best recorded from the cardiac apex and less frequently from the right parasternal and suprasternal areas. However, gradients from the right parasternal area correlated best with cardiac catheterization findings, although recordings could be made from this window in only 49% of the patients. Velocities from the suprasternal window were significantly (p less than 0.01) lower than those from the apex or right parasternal areas. Gradient underestimation from the suprasternal window tended to increase with age of the patient (p less than 0.01). When the maximal Doppler derived gradient from any window was compared with catheterization measurements, the correlation coefficient was 0.86. Gradients derived from Doppler velocities accurately predicted severe (more than 50 mm Hg) gradients at catheterization. Thus, Doppler echocardiography is useful in evaluation of AS when several windows are used for optimal assessment of aortic valve gradient.
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Estenosis de la Válvula Aórtica/fisiopatología , Ecocardiografía/métodos , Adulto , Factores de Edad , Anciano , Velocidad del Flujo Sanguíneo , Cateterismo Cardíaco , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
Doppler echocardiography is useful for detecting and quantifying mitral regurgitation (MR) and mitral stenosis (MS). To determine the prevalence of these abnormalities in patients with mitral anular calcium (MAC), 51 consecutive patients who had an echocardiographic diagnosis of MAC were examined by Doppler ultrasound. Transmitral flow was evaluated to determine the presence of MR or left ventricular inflow obstruction (MS) by continuous and pulsed-wave Doppler echocardiography. The severity of these hemodynamic abnormalities was quantitated by previously described techniques. Eleven patients (22%) had mild MR, 17 (33%) had moderate to severe MR and 4 (8%) had significant MS. Clinical findings such as a systolic murmur, evidence of congestive heart failure, and dyspnea on exertion were not helpful in distinguishing patients with no or mild MR from those who had moderate to severe MR. M-mode measured left atrial size was significantly larger (p less than 0.05) in patients with moderate to severe MR. This study suggests that MR is often associated with MAC, that MS is not a rare finding with MAC, and that Doppler echocardiography can quantitate these lesions in the elderly when symptoms are not specific and physical findings are inconclusive or absent.