Bypass distal de miembros inferiores: análisis de resultados en un servicio de Cirugía Cardiovascular de la Comunidad Valenciana.

INTRODUCCIÓN. La técnica del bypass distal (BPD), con más de medio siglo de historia es actualmente un recurso todavía muy útil para el salvamento de las extremidades isquémicas, si bien los avances tecnológicos actuales permiten cada vez más opciones menos agresivas (técnicas endovasculares). Tanto la forma de presentación temporal y la existencia de cirugías previas en el miembro afecto son aspectos prioritarios a conocer durante la valoración de la isquemia de miembros inferiores. En la literatura aunque sí que se han estudiado estos factores para el bypass infrainguinal en general, no hay una información clara aplicada solo al BPD. HIPÓTESIS. En la cirugía de revascularización de miembros inferiores con la técnica del bypass distal, la forma de presentación temporal y la etiología principal condicionan los resultados en ausencia del factor cirujano. OBJETIVOS. Determinar los resultados de mortalidad (MORT), amputación mayor (AMP) y de amputación mayor en el paciente vivo (PVA) durante los primeros 60 meses según la forma de presentación temporal y la etiología principal. Análisis de factores pronósticos perioperatorios que influyen en los resultados durante los primeros 60 meses. MATERIAL Y MÉTODOS. Es un estudio retrospectivo de todos los BPD realizados de forma consecutiva desde Octubre de 2003 a Junio de 2014 en el Servicio de Cirugía Cardiovascular del Hospital Clínico de Valencia por un mismo cirujano. Se incluyeron pacientes que precisaron una revascularización de bypass a los vasos infrapoplíteos (bypass distal) por una isquemia crítica o aguda. En la forma de presentación temporal se definió un grupo de síndrome de isquemia crónica (SIC) cuando los síntomas comenzaron hacía más de 14 días frente a otro de síndrome de isquemia aguda (SIA) cuando fueron en 14 días o menos. En la etiología principal se consideró como “arteriosclerosis-novo” (ARTN) cuando la causa fue la arteriosclerosis en pacientes sin revascularizaciones infrainguinales quirúrgicas previas, por el contrario, se definió como “postquirúrgico-oclusión” (PQO) cuando existía una revascularización infrainguinal fallida. El análisis de los datos se realizó con el programa estadístico SPSS. Valores de la p < 0.05 se consideraron estadísticamente significativos. Las variables continuas fueron analizadas con el test paramétrico de la T-Student o con el no paramétrico de la U de Mann-Withney. En las variables cualitativas, se utilizó la prueba exacta de Fisher, y como medida de asociación el riesgo relativo. El test de Log Rank comparó la curvas de Kaplan-Meier. Se realizó un análisis multivariado mediante la regresión de Cox para las variables de resultados. RESULTADOS. Se realizó el procedimiento de BPD en 110 miembros de 103 pacientes. Predominaron los varones (82.7%) y la edad media fue de 66.7 años. Los factores de riesgo cardiovascular fueron la exposición previa al tabaco (78.1%), diabetes mellitus (60%), hipertensión arterial (65.5%) y dislipemia (56.4%). Estaban sometidos previamente a diálisis un 4.5%. El 29.1% tenían un procedimiento previo ipsilateral de revascularizacion en sector femoropoplíteo (abierto y/o endovascular). Respecto a la forma de presentación temporal, el 73.6% fueron SIC, fundamentalmente por grados IV de Fontaine. El 88.9% fueron considerados etiología principal (con predominio de la ARTN) y el resto fue una miscelánea de causas, fundamentalmente aneurismas poplíteos (7.3%). La revascularizacion quirúrgica asociada durante el BPD en el sector aortoilíaco fue de un 6.4% (fundamentalmente como bypass axilofemoral), en cambio en el sector femoropoplíteo fue de un 24.5%. La vena safena interna “non-spliced” se utilizó como injerto en un 76.4% de casos, con predominio de la técnica invertida (64.5%). Como injertos alternativos, el composite prótesis-vena fue el más frecuente (17.3%). Hubo un predominio del BPD crural, con un 21.8% de BPD inframaleolar. Respecto a las complicaciones postoperatorias durante el ingreso, un 6% presentaron síndromes coronarios agudos, no hubo complicaciones cerebrales isquémicas ni hemorrágicas y un 15% presentaron morbilidad a nivel de la herida quirúrgica del BPD. Previamente al BPD un 10.9% de los casos tenían una amputación mayor en el miembro contralateral, y durante el seguimiento se produjeron un 13.6% más. Según la forma de presentación temporal, los resultados fueron los siguientes: La MORT precoz del SIC (2.5%) fue menor que en SIA (13.8%), en cambio, no hubo diferencias significativas en la MORT a 12, 36 y 60 meses con 14.9%, 32.0% y 45.1% en el SIC, frente a 17.2%, 25.0% y 35.4% en el SIA. La AMP precoz, 12, 36 y 60 meses del SIC fue menor con 2.5%,11.0%, 16.2% y 21.8% respecto a un 17.2%, 42.1%, 46.9% y 46.9% del SIA. La PVA a 12, 36 y 60 meses fue menor en SIC con un 10.6%,16.0% y 18.1%, respecto al SIA con un 39.1%, 41.7% y 40.0%, pero sin diferencias significativas a 60 meses. Según la etiología principal, los resultados fueron los siguientes: No hubo diferencias en la MORT precoz, a 12, 36 y 60 meses del ARTN con 4.1%,15.0%, 28.3% y 43.7% frente al PQO con 8.3%,18.3%, 23.2% y 38.9% . La AMP precoz fue similar en ARTN (4.1%) y PQO (8.3%), en cambio la AMP a 12, 36 y 60 meses en ARTN (5.5%, 17.4% y 23.1%) fue menor que en PQO (40.7%, 45.6% y 45.6%) . La PVA a 12, 36 y 60 meses fue menor en ARTN con un 10.0%, 13.9% y 17.2%, respecto al PQO con un 40.9%, 43.3% y 41.2%, pero sin diferencias estadísticamente significativas a 60 meses. Los factores perioperatorios independientes en los primeros 60 meses tras el análisis multivariado fueron los siguientes. Para la MORT: la neoplasia previa, la realización de un procedimiento quirúrgico aortoilíaco asociado durante el bypass distal y la aparición de ciertas complicaciones postoperatorias (cardíacas isquémicas, cardíacas no isquémicas o digestivas). Para la AMP: la exposición previa al tabaco, la realización de un procedimiento quirúrgico femoropoplíteo asociado durante el bypass distal, la aparición de complicaciones postoperatorias infecciosas no quirúrgicas, desbridamientos asociados tras el bypass distal y la permeabilidad del bypass distal durante el ingreso. Para la PVA: la exposición previa al tabaco, el procedimiento vascular previo ipsilateral en sector femoropoplíteo, la realización de un procedimiento quirúrgico femoropoplíteo durante el bypass distal y la permeabilidad del bypass distal durante el ingreso. CONCLUSIONES. Los resultados del bypass distal en ausencia del factor cirujano son diferentes según la forma de presentación temporal y según la etiología principal, si bien no están entre los factores perioperatorios predictores independientes de la mortalidad, la amputación y la amputación en el paciente vivo durante los primeros 60 meses.More than half a century after it was first performed, the distal bypass (DBP) technique is still a very useful resort for ischemic limb salvage, although the new technological advances permit lesser aggressive options (endovascular therapy). Key aspects to acknowledge during evaluation of ischemia of the lower extremities are the temporary presentation form and previous operations carried out on the affected limb. These factors have been studied in relation to infrainguinal bypass in general, but medical literature is not clear as to DBP. HYPOTHESIS. In revascularization of lower extremities surgery using the distal bypass technique both the temporary presentation form and the main etiology condition the clinical outcomes in the absence of the surgeon factor. OBJECTIVES. To determine outcomes of mortality (MORT), major amputation (AMP) and major amputation in the living patient (ALP) during the first 60 months depending on the temporary presentation form and the main etiology. To analyze the perioperative prognostic factors that may influence the outcomes in the first 60 months. MATERIAL AND METHODS. This is a retrospective study covering all consecutive DBP performed by the same surgeon from October 2003 to June 2014 in the Department of Cardiovascular Surgery of Hospital Clínico of Valencia. All patients included in the study required bypass revascularization of infrapopliteal vessels (distal bypass) related to critical or acute limb ischemia. The temporary presentation form has been defined as: chronic ischemic syndrome (CIS) when symptoms begin more than 14 days prior to surgery; acute ischemic syndrome (AIS) when there are less than 14 days between the onset and surgery. Regarding the main etiology, two causes were considered: “arterosclerosis- novo” (ARTN) when arterosclerosis was the cause of ischemia and no open infrainguinal revascularizations had been previously performed; the other cause was “postsurgical-occlusion”(PSO) when due to a failing or failed previous open infrainguinal revascularization. The data analysis was calculated using the “SPSS” statistics program. A p-value < 0.05 was considered significant. Continuous variables were analized by the parametric T-Student test or the nonparametric U-Mann-Withney test. Fisher's exact test was used for qualitative variables and the relative risk as a measure of association. Kaplan-Meier curves were compared by the Log Rank. The multivariate analysis for the outcome variables was performed by Cox regression. RESULTS. DBP procedure was performed in 110 limbs of 103 patients. 82.7% were male and mean age was 66.7 years. Cardiovascular risk factors were smokers (78.1%), diabetes mellitus (60%), arterial hypertension (65.5%) and dyslipidemia (56.4%). Dialysis was present in 4.5%. A previous ipsilateral revascularization procedure in the femoropopliteal sector (open and/or endovascular) was performed in 29.1%. With regards to the temporary presentation form, 73.6% were CIS, mainly grade IV of Fontaine. 88.9% were considered as main etiology (mainly ARTN) and the rest as miscellaneous causes (mainly popliteal aneurysms, 7.3%). Associated surgical revascularization during DBP in the aortoiliac sector was 6.4% (mainly as axillofemoral bypass), and 24.5% in the femoropopliteal sector. The “non-spliced” great saphenous vein was the graft in 76.4%, with a predominance of reversed technique (64.5%). As alternative grafts, the composite prosthesis-vein was the most frequent (17.3%). There was a predominance of crural DBP above the 21.8% of inframalleolar DBP. With regards to postoperative complications during hospitalization, 6% presented acute coronary syndromes, none showed cerebral complications (neither ischemic nor hemorrhagic) and 15% suffered DBP surgical wound morbility. 10.9% of cases had a previous contralateral major limb amputation and a further 13.6% suffered contralateral amputation during DBP follow-up. Regarding the temporary presentation form, the results were: Early MORT for CIS (2.5%) was lesser than AIS (13.8%), however, there were no significant differences in MORT at 12, 36 and 60 months with 14.9%, 32.0% and 45.1% for SIC, against 17.2%, 25.0% and 35.4% for AIS. Early, at 12, 36 and 60 months AMP for CIS was lower at 2.5%,11.0%, 16.2% and 21.8%, in comparison with 17.2%, 42.1%, 46.9% and 46.9% for AIS. ALP at 12, 36 y 60 months was lower for CIS at 10.6%,16.0% and 18.1%, with respect to AIS at 39.1%, 41.7% and 40.0%, but with no significant differences at 60 months. Regarding the main etiology, the results were: There were no differences in MORT early, at 12, 36 and 60 months between ARTN, at 4.1%,15.0%, 28.3% and 43.7%, and PSO at 8.3%,18.3%, 23.2% and 38.9%. Early AMP was similar for ARTN (4.1%) and PSO (8.3%); however, AMP at 12, 36 and 60 months for ARTN (5.5%, 17.4% y 23.1%) was lower than PSO (40.7%, 45.6% y 45.6%). ALP at 12, 36 y 60 months was lower for ARTN at 10.0%, 13.9% and 17.2%, against PSO at 40.9%, 43.3% and 41.2%, but with no significant differences at 60 months. Multivariate analysis showed the next independent perioperative factors in the first 60 months. For MORT: previous malignancy, associated surgical revascularization during DBP in the aortoiliac sector and several postoperative complications (ischemic cardiac, non-ischemic cardiac, digestive). For AMP: smokers, associated surgical revascularization during DBP in the femoropopliteal sector, non-surgical infectious postoperative complications, debridements after bypass and distal bypass patency at admission. For ALP: smokers, previous ipsilateral revascularization procedure in the femoropopliteal sector, associated surgical revascularization during DBP in the femoropopliteal sector, distal bypass patency at admission. CONCLUSIONS. The outcomes of distal bypass in the absence of the surgeon factor are different depending on the temporary presentation form and the main etiology. These aspects are not included in the perioperative independent predictor factors of mortality, amputation and amputation in the living patient during the first 60 months

In-memory application-level checkpoint-based migration for MPI programs

This is a post-peer-review, pre-copyedit version of an article published in Journal of Supercomputing. The final authenticated version is available online at: https://doi.org/10.1007/s11227-014-1120-2[Abstract] Process migration provides many benefits for parallel environments including dynamic load balancing, data access locality or fault tolerance. This paper describes an in-memory application-level checkpoint-based migration solution for MPI codes that uses the Hierarchical Data Format 5 (HDF5) to write the checkpoint files. The main features of the proposed solution are transparency for the user, achieved through the use of CPPC (ComPiler for Portable Checkpointing); portability, as the application-level approach makes the solution adequate for any MPI implementation and operating system, and the use of the HDF5 file format enables the restart on different architectures; and high performance, by saving the checkpoint files to memory instead of to disk through the use of the HDF5 in-memory files. Experimental results prove that the in-memory approach reduces significantly the I/O cost of the migration process.Ministerio de Ciencia e Innovación; TIN2010-16735Galicia. Consellería de Economía e Industria; 10PXIB105180P

Resilient MPI applications using an application-level checkpointing framework and ULFM

This is a post-peer-review, pre-copyedit version of an article published in Journal of Supercomputing. The final authenticated version is available online at: https://doi.org/10.1007/s11227-016-1629-7[Abstract] Future exascale systems, formed by millions of cores, will present high failure rates, and long-running applications will need to make use of new fault tolerance techniques to ensure successful execution completion. The Fault Tolerance Working Group, within the MPI forum, has presented the User Level Failure Mitigation (ULFM) proposal, providing new functionalities for the implementation of resilient MPI applications. In this work, the CPPC checkpointing framework is extended to exploit the new ULFM functionalities. The proposed solution transparently obtains resilient MPI applications by instrumenting the original application code. Besides, a multithreaded multilevel checkpointing, in which the checkpoint files are saved in different memory levels, improves the scalability of the solution. The experimental evaluation shows a low overhead when tolerating failures in one or several MPI processes.Ministerio de Economía y Competitividad; TIN2013-42148-PMinisterio de Economía y Competitividad; TIN2014-53522-REDTMinisterio de Economía y Competitividad; BES-2014-068066Galicia. Consellería de Cultura, Educación e Ordenación Universitaria; GRC2013/05

Failure Avoidance in MPI Applications Using an Application-Level Approach

[Abstract] Execution times of large-scale computational science and engineering parallel applications are usually longer than the mean-time-between-failures. For this reason, hardware failures must be tolerated by the applications to ensure that not all computation done is lost on machine failures. Checkpointing and rollback recovery is one of the most popular techniques to provide fault tolerance support to parallel applications. However, when a failure occurs, most checkpointing mechanisms require a complete restart of the parallel application from the last checkpoint. New advances in the prediction of hardware failures have led to the development of proactive process migration approaches, where tasks are migrated in a preventive way when node failures are anticipated, avoiding the restart of the whole application. The work presented in this paper extends an application-level checkpointing framework to proactively migrate message passing interface (MPI) processes when impending failures are notified, without having to restart the entire application. The main features of the proposed solution are: low overhead in failure-free executions, avoiding the checkpoint dumping associated to rolling back strategies; low overhead at migration time, by means of the design of a light and asynchronous protocol to achieve a consistent global state; transparency for the user, thanks to the use of a compiler tool and a runtime library and portability, as it is not locked into a particular architecture, operating system or MPI implementation.Ministerio de Ciencia e Innovación; TIN2010-16735Galicia. Consellería de Economía e Industria; 10PXIB105180P

Reducing the overhead of an MPI application-level migration approach

[Abstract] Process migration provides many benefits for parallel environments including dynamic load balance, data access locality, or fault tolerance. This work proposes a solution that reduces the memory and I/O overhead in an application-level checkpoint-based migration approach. The proposal splits the checkpoint files in order to overlap the writing of the state in the terminating processes with the read and restarting operation in the newly spawned processes. It has been tested using the MPI NAS Parallel Benchmarks, showing encouraging results, both in terms of memory consumption and I/O migration times.Ministerio de Economía y Competitividad; TIN2013-42148-PGalicia. Consellería de Cultura, Educación e Ordenación Universitaria; GRC2013/05

On isomorphism conditions for algebra functors with applications to Leavitt path algebras

We introduce certain functors from the category of commutative rings (and related categories) to that of $\mathbb{Z}$-algebras (not necessarily associative or commutative). One of the motivating examples is the Leavitt path algebra functor $R\mapsto L_R(E)$ for a given graph $E$. Our goal is to find "descending" isomorphism results of the type: if $\mathfrak{F},\mathcal{G}$ are algebra functors and $K\subset K'$ a field extension, under what conditions an isomorphism $\mathfrak{F}(K')\cong \mathcal{G}(K')$ of $K'$-algebras implies the existence of an isomorphism $\mathfrak{F}(K)\cong\mathcal{G}(K)$ of $K$-algebras? We find some positive answers to that problem for the so-called "extension invariant functors" which include the functors associated to Leavitt path algebras, Steinberg algebras, path algebras, group algebras, evolution algebras and others. For our purposes, we employ an extension of the Hilbert's Nullstellensatz Theorem for polynomials in possibly infinitely many variables, as one of our main tools. We also remark that for extension invariant functors $\mathfrak{F},\mathcal{G}$, an isomorphism $\mathfrak{F}(H)\cong\mathcal{G}(H)$, for some Hopf $K$-algebra $H$, implies the existence of an isomorphism $\mathfrak{F}(S)\cong\mathcal{G}(S)$ for any commutative and unital $K$-algebra $S$.Comment: 16 page

Improving Scalability of Application-Level Checkpoint-Recovery by Reducing Checkpoint Sizes

This is a post-peer-review, pre-copyedit version of an article published in New Generation Computing. The final authenticated version is available online at: https://doi.org/10.1007/s00354-013-0302-4[Abstract] The execution times of large-scale parallel applications on nowadays multi/many-core systems are usually longer than the mean time between failures. Therefore, parallel applications must tolerate hardware failures to ensure that not all computation done is lost on machine failures. Checkpointing and rollback recovery is one of the most popular techniques to implement fault-tolerant applications. However, checkpointing parallel applications is expensive in terms of computing time, network utilization and storage resources. Thus, current checkpoint-recovery techniques should minimize these costs in order to be useful for large scale systems. In this paper three different and complementary techniques to reduce the size of the checkpoints generated by application-level checkpointing are proposed and implemented. Detailed experimental results obtained on a multicore cluster show the effectiveness of the proposed methods to reduce checkpointing cost.Ministerio de Ciencia e Innovación; TIN2010-16735Galicia. Consellería de Economía e Industria; 10PXIB105180P

Estandarizacion de metodo PCR-RELP para estudio de polimorfismo de vitamina K Epoxido reductasa (VKORC1 1639G>A)

55 p.Introducción. Polimorfismos de Vitamina K epóxido reductasa (VKORC1) han sido estudiados y se ha evidenciado que afectan en los requerimientos de dosis de anticoagulantes orales. Dentro de los polimorfismos, los más estudiados y que han mostrado mayor influencia en la respuesta a tratamientos con anticoagulantes orales son 1639G>A y 1173 C>T mostrando diferencias en distintas poblaciones étnicas. Objetivo. Estandarizar un método para el estudio del polimorfismo de VKORC1 1639G>A en pacientes con tratamiento anticoagulante oral. Materiales y Método. Se extrajo DNA genómico a partir de leucocitos de sangre periférica de individuos en tratamiento con anticoagulante oral. El polimorfismo VKORC1 1639G>A, fue detectado a través de la técnica PCR-RFLP. Resultados. Se determinó la Tm adecuada para el estudio del polimorfismo y se estableció los volúmenes de MgCl2 y dNTPs adecuados para la reacción. Discusión. Se logró entregar las bases para el estudio del polimorfismo al realizar la estandarización del método. Se plantea la posibilidad de incorporar a la clínica la farmacogenética. Conclusión. Se logró estandarizar la técnica PCR-RFLP para el estudio de variantes alélicas del gen VKORC1 en una población de pacientes con tratamiento anticoagulante oral