Numerical analysis of the pressure drop across highly-eccentric coronary stenoses: application to the calculation of the fractional flow reserve.

BACKGROUND: Fractional flow reverse (FFR) is the gold standard assessment of the hemodynamic significance of coronary stenoses. However, it requires the catheterization of the coronary artery to determine the pressure waveforms proximal and distal to the stenosis. On the contrary, computational fluid dynamics enables the calculation of the FFR value from relatively non-invasive computed tomography angiography (CTA). METHODS: We analyze the flow across idealized highly-eccentric coronary stenoses by solving the Navier-Stokes equations. We examine the influence of several aspects (approximations) of the simulation method on the calculation of the FFR value. We study the effects on the FFR value of errors made in the segmentation of clinical images. For this purpose, we compare the FFR value for the nominal geometry with that calculated for other shapes that slightly deviate from that geometry. This analysis is conducted for a range of stenosis severities and different inlet velocity and pressure waveforms. RESULTS AND CONCLUSIONS: The errors made in assuming a uniform velocity profile in front of the stenosis, as well as those due to the Newtonian and laminar approximations, are negligible for stenosis severities leading to FFR values around the threshold 0.8. The limited resolution of the stenosis geometry reconstruction is the major source of error when predicting the FFR value. Both systematic errors in the contour detection of just 1-pixel size in the CTA images and a low-quality representation of the stenosis surface (coarse faceted geometry) may yield wrong outcomes of the FFR assessment for an important set of eccentric stenoses. On the contrary, the spatial resolution of images acquired with optical coherence tomography may be sufficient to ensure accurate predictions for the FFR value.

Infecciones de repetición en un paciente portador de un sistema de neuromodulación tras la picadura de insecto / Recurrent infection following an insect bite. In a patient with a neuromodulation system

El desarrollo de la tecnología en las últimas décadas del siglo XX ha conllevado disponer de dispositivos, como los neuroestimuladores espinales, que han permitido un salto cualitativo muy importante en el tratamiento de pacientes con dolor severo y de difícil control. En general, las complicaciones que pueden surgir tras la colocación de un electrodo de estimulación de cordones posteriores son mínimas, pero se han descrito algunas de ellas, como son: el desplazamiento del electrodo, la infección y la rotura del electrodo. Presentamos el caso de un paciente joven, ingeniero técnico agrícola, con antecedente de alergia a ácaros del polvo, que presentó tras la picadura de un insecto (Simulium Dam-nosum) en miembro superior derecho, un cuadro de shock séptico, con ingreso durante 48 horas en Reanimación. Durante la hospitalización presentó dolor neuropático severo con escasa respuesta a tratamiento convencional. Tres años y medio después de la picadura del insecto, fue remitido a la Unidad del Dolor de nuestro centro, donde se procedió a primer tiempo de implante de electrodo de estimulación de cordones posteriores, que hubo de ser retirado a los seis días por una infección del electrodo por Estafilococo Aureus. El paciente fue sometido a las pruebas epicutáneas con las sustancias habituales y con las sustancias procedentes de los componentes del neuroestimulador. Se descartó la posibilidad de alergia a alguno de los componentes del sistema implantable que fuera el responsable de una reacción inflamatoria y posterior sobreinfección del catéter. Es necesario destacar que la mejor manera de evitar las infecciones es extremar las medidas de asepsia y debemos valorar la realización de las pruebas de alergia en pacientes con historia de reacciones alérgicas o atopia que aseguren no causarán rechazo del sistema (AU)

Technological developments in the last decade of the 20th century have led to the design of devices such as spinal cord stimulators for the management of severe and intractable pain. Complications after the implantation of the electrodes are infrequent, but some as breakage, infection and displacement have been reported. The case of a young technical agricultural engineer with a medical history of allergy to acarus is described. He developed a septic shock following the sting of an insect (Simu-lium Damnasum) on the top right limb, being admitted to intensive care for 48 hours. During his hospital stay, he had severe neuropathic pain with a poor response to conventional treatment. Three and a half years after this event, the patient was sent to the Pain Management Unit, where the first stage of an electrode implantation for a spinal cord stimulator was carried out. The system was withdrawn after six days due to a Staphylococcus Aureus infection. A series of epicutaneous test for regular substances and for those from the spinal cord stimulator components were made. The likelihood of an allergy to some component of the implantable device, responsible for an inflammatory reaction and subsequent infection of the catheter, was ruled out. It is important to point out that careful asepsis is still the best means to avoid infections. In patients with a medical history of atopia or allergic reactions, allergic tests should be considered as a measure to prevent rejections of devices (AU)

Reorientación de los servicios de urgencias haciael paciente / Reorientation towards the patient in the Emergency Services

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