Carlos García-Montero

RADIAL: A novel primary graft failure risk score in heart transplantation

BACKGROUND Primary graft failure (PGF) is the leading cause of early mortality after heart transplantation (HT). Our aim is to propose a working definition of PGF and to develop a predictive risk score. METHODS PGF was defined by four criteria reflecting significant myocardial dysfunction, severe hemodynamic impairment, early onset after HT, and absence of secondary causes of graft dysfunction. We identified independent risk factors for PGF in a derivation series of 621 HTs and constructed a predictive model. After proving its internal consistency we tested the model in a prospective validation series. RESULTS The incidence and lethality of PGF in our series were 9% and 80%, respectively. We identified 6 multivariate risk factors for PGF (Right atrial pressure ≥ 10 mm Hg, recipient Age ≥ 60 years, Diabetes mellitus, Inotrope dependence, donor Age ≥ 30 years, Length of ischemic time ≥ 240 minutes--i.e., RADIAL). Analysis of isolated right ventricular failure showed similar predictors. The RADIAL score was obtained by adding 1 point for each of these factors present in a given HT. PGF incidence increased significantly as the RADIAL score increased (p < 0.001 for trend). Rates of actual and predicted PGF incidence for RADIAL subgroups showed a good correlation (C-statistic = 0.74). In a prospective validation cohort, RADIAL score kept its predictive ability. CONCLUSIONS PGF as defined by these criteria showed a high impact on early post-HT mortality in our series. The RADIAL score showed good ability to predict the development of PGF, and could be useful in the prevention and early treatment of this complication.

Mechanical behaviour and rupture of normal and pathological human ascending aortic wall

The mechanical properties of aortic wall, both healthy and pathological, are needed in order to develop and improve diagnostic and interventional criteria, and for the development of mechanical models to assess arterial integrity. This study focuses on the mechanical behaviour and rupture conditions of the human ascending aorta and its relationship with age and pathologies. Fresh ascending aortic specimens harvested from 23 healthy donors, 12 patients with bicuspid aortic valve (BAV) and 14 with aneurysm were tensile-tested in vitro under physiological conditions. Tensile strength, stretch at failure and elbow stress were measured. The obtained results showed that age causes a major reduction in the mechanical parameters of healthy ascending aortic tissue, and that no significant differences are found between the mechanical strength of aneurysmal or BAV aortic specimens and the corresponding age-matched control group. The physiological level of the stress in the circumferential direction was also computed to assess the physiological operation range of healthy and diseased ascending aortas. The mean physiological wall stress acting on pathologic aortas was found to be far from rupture, with factors of safety (defined as the ratio of tensile strength to the mean wall stress) larger than six. In contrast, the physiological operation of pathologic vessels lays in the stiff part of the response curve, losing part of its function of damping the pressure waves from the heart.

Factors influencing the mechanical behaviour of healthy human descending thoracic aorta

In recent times, significant effort has been made to understand the mechanical behaviour of the arterial wall and how it is affected by the different vascular pathologies. However, to be able to interpret the results correctly, it is essential that the influence of other factors, such as aging or anisotropy, be understood. Knowledge of mechanical behaviour of the aorta has been customarily constrained by lack of data on fresh aortic tissue, especially from healthy young individuals. In addition, information regarding the point of rupture is also very limited. In this study, the mechanical behaviour of the descending thoracic aorta of 28 organ donors with no apparent disease, whose ages vary from 17 to 60 years, is evaluated. Tensile tests up to rupture are carried out to evaluate the influence of age and wall anisotropy. Results reveal that the tensile strength and stretch at failure of healthy descending aortas show a significant reduction with age, falling abruptly beyond the age of 30. This fact places age as a key factor when mechanical properties of descending aorta are considered.

Influencia de la presión y la temperatura en el comportamiento de la aorta y las carótidas humanas

Introduccion y objetivos La respuesta termomecanica de las arterias humanas es poco conocida a pesar de su importancia para la comprension de la fisiologia arterial, y para la evaluacion y mejora de los procedimientos quirurgicos. El objetivo de este trabajo es aportar por vez primera datos experimentales que muestren como se ve afectada la respuesta mecanica de dos tipos de arterias humanas –aorta y carotida– por los cambios de temperatura. Metodos La respuesta mecanica de las arterias se ha obtenido in vitro a traves de la medicion de las curves presion interior-diametro exterior para 4 temperaturas (17, 27, 37 y 42 °C). Se ha realizado un analisis termomecanico para obtener los coeficientes de dilatacion y la rigidez del material. El estado de la pared arterial se ha evaluado mediante analisis histologico. Resultados Las arterias aorta y carotida aumentan ligeramente su flexibilidad con la temperatura. El coeficiente de dilatacion de ambos vasos depende criticamente de la presion interior aplicada. A bajas presiones, el coeficiente de dilatacion es negativo (el vaso se contrae cuando se calienta), mientras que por encima de cierta presion umbral –distinta para cada tipo de arteria– el coeficiente de dilatacion se hace positivo. Conclusiones El efecto combinado de la presion interior y la temperatura afecta al comportamiento de las arterias y, por ello, debe ser tenido en cuenta al abordar situaciones clinicas que impliquen cambios de temperatura. La intensidad de este efecto depende del tipo de arteria estudiada, lo que requiere la obtencion de datos mas detallados, centrados en los vasos de interes clinico.

The Influence of Pressure and Temperature on the Behavior of the Human Aorta and Carotid Arteries

INTRODUCTION AND OBJECTIVES The thermomechanical behavior of human arteries is still not well characterized despite its importance for understanding arterial physiology, and for evaluating and improving surgical procedures. The aim of this study was to provide, for the first time, experimental data illustrating how the mechanical responses of two types of human artery -the carotid artery and the aorta- are affected by changes in temperature. METHODS The mechanical properties of the arteries were derived in vitro from internal pressure-external diameter curves measured at four different temperatures (i.e., 17, 27, 37 and 42 degree C). Coefficients of expansion and stiffness were obtained by thermomechanical analysis. The condition of the arterial wall was determined histologically. RESULTS The aorta and the carotid artery became slightly more compliant as the temperature increased. In both vessels, the coefficient of expansion depended critically on internal pressure. At low pressures, the coefficient of expansion was negative (i.e., the vessel contracted when heated), whereas close to a specific threshold pressure, which is different for each type of artery, the coefficient became positive. CONCLUSIONS The mechanical behavior of arteries is affected by the combination of internal pressure and temperature. Consequently, the effect of this combination should be taken into account in clinical situations involving a change in temperature. Moreover, the strength of the effect depends on the type of artery under study. As a result, more detailed experimental data focusing on vessels of clinical interest are required.

Implicaciones pronósticas de la morfología asimétrica en la implantación de prótesis aórticas transcatéter: A propósito de un caso

Transcatheter implantation of aortic valve prostheses is being performed with increasing frequency in patients with severe symptomatic aortic stenosis who are at high surgical risk. Either a transfemoral or a transapical approach is employed. Complications related to the procedure are relatively uncommon, but they provide information that is very useful for broadening our knowledge of the pathophysiology of prosthesis dysfunction. A 76-year-old man with severe aortic stenosis underwent transcatheter aortic valve implantation because of high surgical risk due to ischemic heart disease and severe chronic obstructive pulmonary disease. Intraoperative transesophageal echocardiogram (TEE) performed prior to the procedure revealed a severely calcified aortic valve, especially left coronary (Thebesian) valve; the ejection fraction was 42%. Balloon valvuloplasty was carried out, followed by implantation of a 26-mm SAPIEN valve (Edwards Lifesciences; Irvine, California, USA), performed without complications. Immediately after inflation, TEE confirmed that the aortic prosthesis was well positioned, with adequate valve mobility. However, probably due to the severe eccentric calcification, the prosthesis had an asymmetric morphology, with an oval shape and abnormal stretching of the valve, which was oriented along the major axis (Fig. 1). Despite this appearance, the results of the procedure were considered to be satisfactory because the prosthesis appeared to be functioning normally, with mild central and minimal paravalvular regurgitation. Initially, the patient progressed well and was extubated on the first day; however, the next day he developed acute pulmonary edema, with rapid clinical deterioration. An emergency echocardiogram revealed severe aortic regurgitation, and the patient underwent an emergency intervention involving extracorporeal surgery with implantation of a Perimount bioprosthesis (Edwards Lifesciences; Irvine, California, USA). The patient died of cardiogenic shock during the postoperative period. Visual inspection of the explanted SAPIEN valve showed an elliptical morphology with a major diameter of 27 mm and a minor diameter of 20 mm, measurements that agree with those made by means of TEE during the procedure (Fig. 2). Moreover, as documented with TEE, one of the valves was abnormally taut and elongated, with limited mobility. The Edwards-SAPIEN valve is a prosthesis made of bovine pericardium mounted on an expandable stent that is placed in subcoronary position. Nine years after the first case in humans, favorable results have been reported for both the transfemoral and the transapical approach. The complete and symmetric expansion of the prosthesis in the aortic annulus is very important for its normal function and the aim should be to achieve this in every case. In fact, when the valve has a circular aspect, a success rate of 98% can be expected, whereas an oval morphology is associated with suboptimal function and durability. In our case, the massive presence of eccentric calcium in the left coronary valve of the native valve presumably provoked abnormal stress in the anteroposterior direction and impeded uniform circular expansion. In fact, the major diameter of the prosthesis was greater than the nominal diameter, which indicates that the problem was not an insufficient inflation pressure, but the lack of deformability of the annulus in a given direction. The consequence was an abnormal tautness in the valve oriented along the major axis, which resulted in limited mobility, inadequate coaptation, and finally, severe aortic regurgitation. Although this aortic insufficiency was considered to be mild at the end of the procedure because of the narrow width of the jet, the abnormal geometry of the prosthesis may have been what caused the progression to severe regurgitation during the postoperative period. Severe asymmetric valve calcification is a risk factor for incomplete expansion of the prosthesis and requires special attention to technique, even balloon oversizing. The failure to

Utilidad del ultrasonido intravascular para la medición de la luz aórtica

El ultrasonido intravascular (IVUS) se ha utilizado con exito para guiar la implantacion de endoprotesis en aorta toracica. Sin embargo, su precision para medir la luz aortica no esta definitivamente establecida. Evaluamos con IVUS a 13 pacientes con enfermedad de la aorta toracica, comparando el diametro luminal con las medidas de tomografia computarizada (TC) o resonancia magnetica. Se obtuvieron 31 mediciones comparables. La correlacion fue buena (r = 0,98; p 10%). En conclusion, el IVUS resulta fiable para la medicion de diametros aorticos, especialmente en segmentos concentricos donde se fijan las endoprotesis, y puede complementar las tecnicas de imagen convencionales.

Intravascular Ultrasound Measurement of the Aortic Lumen

Intravascular ultrasound (IVUS) has been successfully used to guide the implantation of stents in the thoracic aorta. However, its accuracy in measuring the diameter of the aortic lumen has not been clearly established. Thirteen patients with thoracic aortic disease underwent IVUS, and lumen diameter measurements were compared with those obtained by CT or magnetic resonance imaging. A total of 31 comparable measurements were obtained. The correlation was good (r=0.98; P< .001), with IVUS tending to give a larger minimum diameter than CT (systematic error, 0.59+/-1.8 mm; P=.077). Given that the aorta is often not circular, the diameter obtained by IVUS was also compared to the mean diameter obtained by CT, and it was found that these two measurements were more closely related (P=.425), except in aortic segments with significant eccentricity (i.e., >10%). In conclusion, IVUS was a reliable tool for measuring the diameter of the aorta, particularly in concentric segments where stents are normally placed. Consequently, IVUS could supplement conventional imaging techniques.

206. Reparación mitral como tratamiento de la insuficiencia mitral crónica. Estudio de 119 casos

Objetivos Siempre que sea tecnicamente posible, la reparacion valvular (RV) es la tecnica de eleccion en el tratamiento de la insuficiencia mitral. Presentamos la experiencia de nuestro servicio en el abordaje quirurgico de la insuficiencia mitral mediante la aplicacion de distintas tecnicas reparadoras. Metodos Se han intervenido un total de 119 pacientes desde 1997-2010, realizandose un estudio descriptivo retrospectivo de dicha serie. Resultados Del total de pacientes un 62% eran hombres, 38% eran mujeres, con una edad media de 61,4 anos. En cuanto a la etiologia de la insuficiencia mitral, en un 76% era degenerativa, 12,8% isquemica, 6,4% endocarditica, 2,4% reumatica y 2,4% por miocardiopatia dilatada. Existia disfuncion ventricular grave en 12,8% de los casos, produciendose un fallecimiento en el postoperatorio inmediato. El resultado posquirurgico medido por ecocardiografia transesofagica (ETE) intraoperatoriamente fue insuficiencia mitral grado 0-1 en 94,4% de los casos. La mortalidad a los 30 dias de cirugia fue de 6,4%. La necesidad de intervencion, con el tiempo, relacionada con la propia cirugia fue del 3,2%. La serie presenta un seguimiento medio de 48,5 meses, y en la actualidad estan exentos de anticoagulacion un 73% de los pacientes de la serie. Conclusiones La cirugia de reparacion mitral es una tecnica segura y eficaz que permite corregir adecuadamente el vicio valvular. Su morbimortalidad hospitalaria es baja, presentando excelentes resultados a corto y medio plazo, ademas de evitar todas las complicaciones propias de las protesis.

221. Experiencia de la asistencia levitronix centrimag en 17 casos

Objetivos La asistencia ventricular Levitronix Centrimag es una bomba centrifuga disenada para el soporte circulatorio, en shock cardiogenico, o como complemento en asistencia respiratoria para lavar mejor el dioxido de carbono, durante un corto espacio de tiempo. El objetivo es mostrar nuestra experiencia con la Levitronix Centrimag uni o biventricular. Metodos Entre febrero de 2008 y marzo de 2010, en 17 pacientes fue implantada la Levitronix Centrimag. La media de edad fue de 55 anos (rango 43-65). Las indicaciones para la colocacion de la asistencia fueron en un caso por tormenta arritmica incontrolable pretrasplante (biventricular), tres sindrome de bajo gasto pretrasplante (izquierda), tres sindrome poscardiotomia (derecha), cuatro casos por fallo primario del injerto postrasplante (derecha) y seis como bypass femorofemoral venovenoso asociado a un oxigenador de membrana. Resultados La supervivencia a los 30 dias de los pacientes fue del 46% (8 pacientes). La media de dias de utilizacion de la asistencia fue de 9 (rango 5-17). La mayor supervivencia fue en los pacientes en los que se utilizo con fallo primario derecho postrasplante, en los que sobrevivieron un 75%. En los tres pacientes que tras la colocacion de la asistencia estaban en lista de espera de trasplante no se llego a realizar por complicaciones infecciosas. Como terapia respiratoria tuvo una eficacia del 33%. Ninguno de los pacientes presento complicaciones embolicas ni hemorragicas. Conclusiones La asistencia Levitronix Centrimag es una opcion real como terapia de recuperacion cardiaca o pulmonar a corto plazo o como puente al trasplante.