Samuel Cordova - Academia.edu (original) (raw)

Papers by Samuel Cordova

Research paper thumbnail of Importance of hourly multi-bus unit commitment models in the context of high adoption of variable renewable energies: A chilean example

2017 IEEE PES Innovative Smart Grid Technologies Conference - Latin America (ISGT Latin America), 2017

The increasing levels of Variable Renewable Energies (VRE) require additional levels of flexibili... more The increasing levels of Variable Renewable Energies (VRE) require additional levels of flexibility in present power systems due to their intermittency and the resulting needs of reserve for increasing/reducing the generation with enough speed to maintain the system balance. In this context, the traditional long-term hydrothermal optimal dispatch models are not sufficient to adequately represent this situation, particularly in systems with hydro reservoirs that can store water from one period to another. These models do not use sequential representation of time periods (on the contrary, they work with load blocks) and they do not incorporate most of the non-linear constraints to model specific characteristics such as: minimum power, ramp up/down rates, stabilization times, minimum time in service, minimum down-time, etc. Therefore, more detailed models must be used to comprehensively represent the impact of VRE in the system operation. To assess the true cost of power system operation with high adoption of VRE, this work develops a detailed multi-bus hourly unit commitment model with all nonlinear constraints, showing the importance of this type of model for assessing cycling and start-up in the new VRE paradigm.

Research paper thumbnail of An Efficient Forecasting-Optimization Scheme for the Intraday Unit Commitment Process Under Significant Wind and Solar Power

IEEE Transactions on Sustainable Energy, 2018

Due to their uncertain and variable nature, the large-scale integration of wind and solar power p... more Due to their uncertain and variable nature, the large-scale integration of wind and solar power poses significant challenges to the generator scheduling process in power systems. To support this process, system operators require using repeatedly updated forecasts of the best possible quality for renewable power. Motivated by this, the present work aims to study the benefits of incorporating spatiotemporal dependence and seasonalities into probabilistic forecasts for the intra-day unit commitment (UC) process. With this purpose, a highly efficient forecasting-optimization scheme is proposed, which is composed by a detrended periodic vector autoregressive model and a technology-clustered interval UC model. The proposed approach is tested on a 120 GW power system with 210 conventional generators using real wind and solar measurements, and compared to existing deterministic and stochastic UC techniques alongside standard forecasting methods. Extensive computational experiments show that: i) the incorporation of spatiotemporal dependence and seasonalities into forecasts translates in a reduction of up to 1.55% in operational costs for a daily UC relative to standard practice; ii) the application of intra-day instead of daily UC runs further reduce operational costs in up to 1.51%; iii) the proposed forecasting-optimization scheme takes less than 10 hours to simulate a whole year. Index Terms-unit commitment, interval optimization, forecasting, autoregressive models, solar power, wind power, renewable uncertainty.

Research paper thumbnail of Automatic fish hook setter

Research paper thumbnail of Significant Down-Stream Activation of the Rho A/ Rho Kinase Intracellular Signaling Pathway in Patients with Type 2 Diabetes and Hypertension

Journal of the American College of Cardiology, 2016

Research paper thumbnail of Knowledge Level Influence in Protective Attitudes and Practices against the Risk of HIV/AIDS in Students of Private Peruvian High Schools

Objective: To determine the influence of knowledge on protective attitudes and practices against ... more Objective: To determine the influence of knowledge on protective attitudes and practices against the risk of HIV/AIDS in Peruvian students from exclusively private schools from the three regions of the country. Methodology: Following a correlational-comparative design, a sample of 849 Peruvian students from 52 private high schools was selected using cluster, stratified, and systematic sampling. Data was collected from adolescents and parents who signed informed consents, and was analyzed using the Kruskal-Wallis test and Spearman correlations. Results: Results indicate that the level of knowledge influences attitudes but not protective practices against the risk of HIV/AIDS (r =.218, pConclusions: Private school students’ knowledge about HIV/AIDS shows a highly significant influence (pKeywords: HIV/AIDS; protective attitudes & practices; private high schools.

Research paper thumbnail of Influence of Religiosity on HIV/AIDS-Related Behaviors of Adolescents 1

The 6 th of the 8 United Nations Millennium Development Goals is to combat HIV/AIDS, which affect... more The 6 th of the 8 United Nations Millennium Development Goals is to combat HIV/AIDS, which affects the fulfillment of 4 other goals. Combating HIV/AIDS depends on effective sex education and the care of AIDS patients across countries, cultures, and all kinds of boundaries. Is religion a protective factor against HIV/AIDS, or is it a barrier? Literature is divided on this issue. The purpose of this study was to determine the influence of religiosity on attitudes and protective practices against the risk of HIV/AIDS in 849 Peruvian students from 52 private schools in the 3 cities: Lima, Cuzco and Iquitos. Results showed that the level of religiosity and attitudes are not significantly related, but religion did encourage protective practices against the risk of HIV/AIDS (r = .059, p > .05, r = -.156 p < 0.01). This establishes a low relationship between religiosity and protective practices against the risk of HIV/AIDS. Attitudes were also found to have a highly significant correl...

Research paper thumbnail of 447 Usefulness of non-invasive coronariography by computed tomography prior to valvular surgery

European Journal of Echocardiography, 2006

Background and purpose: The mitral annulus (MA) is an integral part of the mitral apparatus givin... more Background and purpose: The mitral annulus (MA) is an integral part of the mitral apparatus giving attachment to the left ventricle (LV) and the atrium (LA). The MA motion during systole has been reported to be proportional to the LV systolic function. This study was conducted to investigate if systolic MA motion that is related to LV systolic function has an impact on LA filling using real-time 3D echocardiography (RT3DE). Methods: RT3DE was performed in 11 normal controls with normal LV systolic function (EF 57±4%) and 12 patients with global LV systolic dysfunction (EF 24±5%). LV volumetric data were segmented into 16 rotational apical planes (angle increment =11.25°) around the rotational axis from the apex through the center of the MA, using newly developed 3D computer software (TomTec, Co. Germany). Two hinge points of leaflets were traced in each plane during early and late systole. The MA was then automatically reconstructed with those 32 traced points. 3D surface (3DMAA) and 2D projected areas (2DMAA) of the annulus during early and late systole were automatically calculated. LA volume (LAV) measurement was identified by the planimetry on the 8 rotational apical planes using 3D computer software (4D Cardio View, TomTec, Co.). All measurements were corrected by BSA (c) for the comparison between two groups. Systolic changes of all geometrical MA parameters and LAV were estimated by their fractional changes (%). Results: c3DMAA, c2DMAA and cLAV were significantly (p<.01) increased in patient group but their fractional increases during systole were significantly (p<.01) reduced comparing with controls. Fractional increases of c3DMAA (r=0.83, p<.01) and c2DMAA (r=0.88, p<.01) showed close correlations with LVEF. Fractional icreases of both c3DMAA (r=0.89, p<.01) and c2DMAA (r=0.90, p<.01) also showed close relationships with that of cLAV. Conclusion: Systolic enlargement of the mitral annulus was closely related to the LV systolic function and the fractional of change of the annulus may significantly affect left atrial filling during systole.

Research paper thumbnail of Speckle tracking derived left atrial strain and strain rate are related to high sensitive C reactive protein in obese adolescents

Research paper thumbnail of Fibroelastoma papilar múltiple de válvula aórtica complicado de accidente vascular encefálico embólico.: Caso clínico

Revista médica de Chile, 2001

... Samuel Córdova A, Ricardo Zalaquett S, Benedicto Chuaqui J, Pablo Casanegra P, Gastón Chamorr... more ... Samuel Córdova A, Ricardo Zalaquett S, Benedicto Chuaqui J, Pablo Casanegra P, Gastón Chamorro S. ... Luego se liberó la comisura fusionada entre el velo coronariano izquierdo y el no ... 8. Yee HC, Nwosu JE, Lil AD, Velasco M, Millman A. Echocardiographic Features of ...

Research paper thumbnail of Increased Rho-Kinase Activity in Hypertensive Patients With Left Ventricular Hypertrophy

American Journal of Hypertension, 2013

The small guanosine triphosphatase Rho and its target Rhokinase (ROCK) play significant roles in ... more The small guanosine triphosphatase Rho and its target Rhokinase (ROCK) play significant roles in both blood pressure regulation and vascular smooth muscle contraction. Rho is activated by agonists of receptors coupled to cell membrane G protein (such as angiotensin II, endothelin, or noradrenalin), by growth factors, or by cytokines. 1-4 Once Rho is activated, it translocates to the cell membrane where it activates ROCK. Then ROCK phosphorylates myosin light chain phosphatase, which is then inhibited. This sequence stimulates vascular smooth muscle contraction, stress fiber formation, and cell migration. In this way, Rho and ROCK activation have important effects on several cardiovascular diseases. 2-6 Additionally, there is experimental evidence on the significant role of ROCK activation in the development of cardiac hypertrophy, remodeling, and ventricular dysfunction. In Dahl salt-sensitive hypertensive rats, increased left ventricular weight was significantly ameliorated by using the ROCK inhibitor Y-276327. 7 Upregulated RhoA protein, ROCK gene expression, and myosin lightchain phosphorylation in the hypertrophy stage were also suppressed by the ROCK inhibitor. 7 In hypertensive rats, the ROCK inhibitor fasudil attenuated myocardial fibrosis possibly through suppression of monocyte/macrophage infiltration of the heart. 8 Moreover, ROCK is significantly activated in the aortic wall in normotensive rats with genetically high angiotensin I-converting enzyme and angiotensin II, and it causes activation of genes that promote vascular remodeling, such as monocyte chemoattractant protein 1, transforming growth factor β1, and plasminogen activator inhibitor 1, and also increases vascular oxidative stress. 9 In Dahl salt-sensitive hypertensive

Research paper thumbnail of Veinte años de cirugía reparadora de la válvula mitral

Revista médica de Chile, 2014

JoSefina almeida Z. a , aldo meneSeS o. a , cecilia muñoZ c., Samuel cóRdova a. Twenty years of m... more JoSefina almeida Z. a , aldo meneSeS o. a , cecilia muñoZ c., Samuel cóRdova a. Twenty years of mitral valve repair. An experience in 322 patients Background: Mitral valve repair is the preferred procedure for the surgical treatment of mitral valve insufficiency (MI), procedure that we initiated 20 years ago. Aim: To assess our experience and long-term results of mitral valve repair. Patients and Methods: The database of the cardiology department was reviewed for the period between December 1991 and December 2012. A total of 322 patients aged 18 to 89 years (62% males) undergoing mitral valve repair were identified. Long-term survival information was obtained consulting death certificate records of the Chilean Identification Service. The latest echocardiogram available was analyzed. Results: MI was degenerative in 144 patients (45%) and ischemic in 104 (32%). A prosthetic ring was used in all ischemic and in 92% of non-ischemic MI. Operative mortality was 7.5%, 13% in ischemic and 4.4% in non-ischemic MI (p < 0.01). Overall long-term survival was 14.1 years; 9.3 and 16 years for ischemic and non-ischemic MI, respectively (p < 0.001). Survival at 5, 10, 15 and 20 years was 79, 63, 54 and 42%, respectively. For degenerative MI survival at 5 and 10 years was 90 and 76% and for ischemic MI, it was 64 and 44%, respectively (p < 0.001). On a multivariate analysis the main predictors of late mortality were age, associated valvular disease and ischemic etiology. Echocardiographic follow-up was available for 223 patients; MI was absent in 53% and was mild in 29%. Conclusions: In a 20 years follow-up, mitral valve repair for MI had excellent long-term survival and echocardiographic results. The most common etiologies of MI were degenerative and ischemic diseases. The latter had a worst prognosis. The main predictors of long term mortality were age, associated valvular disease and ischemic etiology.

Research paper thumbnail of Enfermedad cardíaca por carcinoide

Revista chilena de cardiología, 2011

Research paper thumbnail of Endocarditis infecciosa por Listeria monocytogenes: revisión de la literatura a partir de un caso clínico

Revista chilena de infectología, 2013

Research paper thumbnail of Strain y Strain rate auricular izquierdo evaluado por speckle tracking está relacionado a PCR ultrasensible en adolescentes obesos

Revista chilena de cardiología, 2011

Research paper thumbnail of 279 Usefulness of tissue doppler imaging in the detection of residual constriction post-pericardiectomy

European Journal of Echocardiography, 2006

Objectives: Vascular abnormalities are hallmarks of almost all systemic sclerosis patients. Impai... more Objectives: Vascular abnormalities are hallmarks of almost all systemic sclerosis patients. Impaired relaxation of the left ventricle is also characteristic for scleroderma heart disease. The aim of our study was to determine whether parameters of arterial stiffness correlate with echocardiographic indices of left ventricular relaxation impairment. Material: 21 patients with limited and diffuse scleroderma (18 women, mean age: 55±9 years) were studied. Methods: Parameters of local and systemic arterial stiffness (pulse wave velocity: PWV; augmentation index: Aix) were determined by automatic brachial pulse wave analysis (Arteriograph®). The same parameters and elastic modulus (Ep), stiffness index (ß), arterial compliance (AC) were measured on left brachial and common carotid arteries by echo-tracking (Aloka ProSound 5500). Indices of diastolic function were also determined with the same ultrasound system: in addition to the conventional Doppler parameters of the transmitral flow-early (E) and late (A) diastolic velocities, deceleration time (DT), isovolumic relaxation time (IVRT)-myocardial early (Ea) and late (Aa) diastolic velocities were measured at the lateral border of the mitral annulus using tissue Doppler imaging. E/A and E/Ea ratios were calculated. Simple associations between the variables were estimated by Pearson's method. Results: Carotid Ep showed significant correlations with both A (r=0.537, p<0.05) and E/A (r=-0.500, p<0.05) values, and correlated with IVRT also significantly (r=0.489, p<0.05). Carotid ß correlated with A (r=0.479, p<0.05), E/A (r=-0.548, p<0.05) and IVRT (r=0.564, p<0.01). Carotid AC correlated with A (r=-0.512, p<0.05), E/A (r=0.551, p<0.05) and IVRT values (r=-0.436, p<0.05). Carotid PWV and Aix showed similarly significant correlations with A, E/A, IVRT and with A and E/A values, respectively. Ep, ß and PWV determined by pulse-wave analysis and brachial artery echo-tracking did not correlate with the echocardiographic parameters of the left ventricular diastolic function. Brachial AC showed a significant correlation with A (r=-0.478, p<0.05) and DT (r=0.469, p<0.05). Significant correlation was found between Aix measured by pulse-wave analysis and Aa (r=0.560, p<0.05). Conclusion: Distensibility of elastic arteries correlates well with the echocardiographic indices of the left ventricular diastolic function, but stiffness of muscular type arteries is less useful to predict the degree of diastolic impairment. Selected parameters of arterial stiffness are good predictors of diastolic dysfunction in scleroderma patients ±.

Research paper thumbnail of Insuficiencia tricuspídea aislada

Revista chilena de cardiología, 2009

Research paper thumbnail of Asociación entre strain y strain rate auricular izquierdo evaluado por speckle tracking y fibrilación auricular post cirugía de revascularización miocárdica

Revista chilena de cardiología, 2011

Research paper thumbnail of Niveles de péptido natriurético cerebral y su relación con capacidad funcional y hemodinamia pulmonar en pacientes con hipertensión pulmonar primaria: Correlation with functional capacity and hemodynamic parameters

Revista médica de Chile, 2006

Research paper thumbnail of Falla cardio-respiratoria severa tratada con asistencia cardiopulmonar extracorpórea: Caso clínico

Revista médica de Chile, 2002

... Figura 3. Gráfico que muestra la evolución de la PaO 2 , proteína C reactiva (PCR), y flujo d... more ... Figura 3. Gráfico que muestra la evolución de la PaO 2 , proteína C reactiva (PCR), y flujo de la bomba centrífuga durante los cinco días de estadía en ventilador. Se aprecia la mejoría inmediata de la PaO 2 al entrar en asistencia ...

Research paper thumbnail of Diagnostic value of cerebrospinal fluid adenosine deaminase determination

Scandinavian Journal of Infectious Diseases, 1991

We measured the activity of adenosine deaminase (ADA) in the cerebrospinal fluid of 3 patients wi... more We measured the activity of adenosine deaminase (ADA) in the cerebrospinal fluid of 3 patients with tuberculous meningitis, 38 with viral meningitis, 15 with bacterial meningitis, 5 with malignant lymphoma, 11 with cerebrovascular diseases and 13 with miscellaneous neurological disorders. The highest ADA activities were observed in patients with tuberculous meningitis (median 21.3 U/l, range 20.0-23.0) and lymphoma (13.0 U/l, range 4.0-25.0). The sensitivity of the test for diagnosing tuberculous meningitis was 100% and the specificity 99% when a cut-off value of 20.0 U/l was used. We conclude that determination of ADA in cerebrospinal fluid is useful for the diagnosis of tuberculous meningitis, but that high activity also can be seen in some other CNS disorders, e.g. lymphoma with meningeal involvement.

Research paper thumbnail of Importance of hourly multi-bus unit commitment models in the context of high adoption of variable renewable energies: A chilean example

2017 IEEE PES Innovative Smart Grid Technologies Conference - Latin America (ISGT Latin America), 2017

The increasing levels of Variable Renewable Energies (VRE) require additional levels of flexibili... more The increasing levels of Variable Renewable Energies (VRE) require additional levels of flexibility in present power systems due to their intermittency and the resulting needs of reserve for increasing/reducing the generation with enough speed to maintain the system balance. In this context, the traditional long-term hydrothermal optimal dispatch models are not sufficient to adequately represent this situation, particularly in systems with hydro reservoirs that can store water from one period to another. These models do not use sequential representation of time periods (on the contrary, they work with load blocks) and they do not incorporate most of the non-linear constraints to model specific characteristics such as: minimum power, ramp up/down rates, stabilization times, minimum time in service, minimum down-time, etc. Therefore, more detailed models must be used to comprehensively represent the impact of VRE in the system operation. To assess the true cost of power system operation with high adoption of VRE, this work develops a detailed multi-bus hourly unit commitment model with all nonlinear constraints, showing the importance of this type of model for assessing cycling and start-up in the new VRE paradigm.

Research paper thumbnail of An Efficient Forecasting-Optimization Scheme for the Intraday Unit Commitment Process Under Significant Wind and Solar Power

IEEE Transactions on Sustainable Energy, 2018

Due to their uncertain and variable nature, the large-scale integration of wind and solar power p... more Due to their uncertain and variable nature, the large-scale integration of wind and solar power poses significant challenges to the generator scheduling process in power systems. To support this process, system operators require using repeatedly updated forecasts of the best possible quality for renewable power. Motivated by this, the present work aims to study the benefits of incorporating spatiotemporal dependence and seasonalities into probabilistic forecasts for the intra-day unit commitment (UC) process. With this purpose, a highly efficient forecasting-optimization scheme is proposed, which is composed by a detrended periodic vector autoregressive model and a technology-clustered interval UC model. The proposed approach is tested on a 120 GW power system with 210 conventional generators using real wind and solar measurements, and compared to existing deterministic and stochastic UC techniques alongside standard forecasting methods. Extensive computational experiments show that: i) the incorporation of spatiotemporal dependence and seasonalities into forecasts translates in a reduction of up to 1.55% in operational costs for a daily UC relative to standard practice; ii) the application of intra-day instead of daily UC runs further reduce operational costs in up to 1.51%; iii) the proposed forecasting-optimization scheme takes less than 10 hours to simulate a whole year. Index Terms-unit commitment, interval optimization, forecasting, autoregressive models, solar power, wind power, renewable uncertainty.

Research paper thumbnail of Automatic fish hook setter

Research paper thumbnail of Significant Down-Stream Activation of the Rho A/ Rho Kinase Intracellular Signaling Pathway in Patients with Type 2 Diabetes and Hypertension

Journal of the American College of Cardiology, 2016

Research paper thumbnail of Knowledge Level Influence in Protective Attitudes and Practices against the Risk of HIV/AIDS in Students of Private Peruvian High Schools

Objective: To determine the influence of knowledge on protective attitudes and practices against ... more Objective: To determine the influence of knowledge on protective attitudes and practices against the risk of HIV/AIDS in Peruvian students from exclusively private schools from the three regions of the country. Methodology: Following a correlational-comparative design, a sample of 849 Peruvian students from 52 private high schools was selected using cluster, stratified, and systematic sampling. Data was collected from adolescents and parents who signed informed consents, and was analyzed using the Kruskal-Wallis test and Spearman correlations. Results: Results indicate that the level of knowledge influences attitudes but not protective practices against the risk of HIV/AIDS (r =.218, pConclusions: Private school students’ knowledge about HIV/AIDS shows a highly significant influence (pKeywords: HIV/AIDS; protective attitudes & practices; private high schools.

Research paper thumbnail of Influence of Religiosity on HIV/AIDS-Related Behaviors of Adolescents 1

The 6 th of the 8 United Nations Millennium Development Goals is to combat HIV/AIDS, which affect... more The 6 th of the 8 United Nations Millennium Development Goals is to combat HIV/AIDS, which affects the fulfillment of 4 other goals. Combating HIV/AIDS depends on effective sex education and the care of AIDS patients across countries, cultures, and all kinds of boundaries. Is religion a protective factor against HIV/AIDS, or is it a barrier? Literature is divided on this issue. The purpose of this study was to determine the influence of religiosity on attitudes and protective practices against the risk of HIV/AIDS in 849 Peruvian students from 52 private schools in the 3 cities: Lima, Cuzco and Iquitos. Results showed that the level of religiosity and attitudes are not significantly related, but religion did encourage protective practices against the risk of HIV/AIDS (r = .059, p > .05, r = -.156 p < 0.01). This establishes a low relationship between religiosity and protective practices against the risk of HIV/AIDS. Attitudes were also found to have a highly significant correl...

Research paper thumbnail of 447 Usefulness of non-invasive coronariography by computed tomography prior to valvular surgery

European Journal of Echocardiography, 2006

Background and purpose: The mitral annulus (MA) is an integral part of the mitral apparatus givin... more Background and purpose: The mitral annulus (MA) is an integral part of the mitral apparatus giving attachment to the left ventricle (LV) and the atrium (LA). The MA motion during systole has been reported to be proportional to the LV systolic function. This study was conducted to investigate if systolic MA motion that is related to LV systolic function has an impact on LA filling using real-time 3D echocardiography (RT3DE). Methods: RT3DE was performed in 11 normal controls with normal LV systolic function (EF 57±4%) and 12 patients with global LV systolic dysfunction (EF 24±5%). LV volumetric data were segmented into 16 rotational apical planes (angle increment =11.25°) around the rotational axis from the apex through the center of the MA, using newly developed 3D computer software (TomTec, Co. Germany). Two hinge points of leaflets were traced in each plane during early and late systole. The MA was then automatically reconstructed with those 32 traced points. 3D surface (3DMAA) and 2D projected areas (2DMAA) of the annulus during early and late systole were automatically calculated. LA volume (LAV) measurement was identified by the planimetry on the 8 rotational apical planes using 3D computer software (4D Cardio View, TomTec, Co.). All measurements were corrected by BSA (c) for the comparison between two groups. Systolic changes of all geometrical MA parameters and LAV were estimated by their fractional changes (%). Results: c3DMAA, c2DMAA and cLAV were significantly (p<.01) increased in patient group but their fractional increases during systole were significantly (p<.01) reduced comparing with controls. Fractional increases of c3DMAA (r=0.83, p<.01) and c2DMAA (r=0.88, p<.01) showed close correlations with LVEF. Fractional icreases of both c3DMAA (r=0.89, p<.01) and c2DMAA (r=0.90, p<.01) also showed close relationships with that of cLAV. Conclusion: Systolic enlargement of the mitral annulus was closely related to the LV systolic function and the fractional of change of the annulus may significantly affect left atrial filling during systole.

Research paper thumbnail of Speckle tracking derived left atrial strain and strain rate are related to high sensitive C reactive protein in obese adolescents

Research paper thumbnail of Fibroelastoma papilar múltiple de válvula aórtica complicado de accidente vascular encefálico embólico.: Caso clínico

Revista médica de Chile, 2001

... Samuel Córdova A, Ricardo Zalaquett S, Benedicto Chuaqui J, Pablo Casanegra P, Gastón Chamorr... more ... Samuel Córdova A, Ricardo Zalaquett S, Benedicto Chuaqui J, Pablo Casanegra P, Gastón Chamorro S. ... Luego se liberó la comisura fusionada entre el velo coronariano izquierdo y el no ... 8. Yee HC, Nwosu JE, Lil AD, Velasco M, Millman A. Echocardiographic Features of ...

Research paper thumbnail of Increased Rho-Kinase Activity in Hypertensive Patients With Left Ventricular Hypertrophy

American Journal of Hypertension, 2013

The small guanosine triphosphatase Rho and its target Rhokinase (ROCK) play significant roles in ... more The small guanosine triphosphatase Rho and its target Rhokinase (ROCK) play significant roles in both blood pressure regulation and vascular smooth muscle contraction. Rho is activated by agonists of receptors coupled to cell membrane G protein (such as angiotensin II, endothelin, or noradrenalin), by growth factors, or by cytokines. 1-4 Once Rho is activated, it translocates to the cell membrane where it activates ROCK. Then ROCK phosphorylates myosin light chain phosphatase, which is then inhibited. This sequence stimulates vascular smooth muscle contraction, stress fiber formation, and cell migration. In this way, Rho and ROCK activation have important effects on several cardiovascular diseases. 2-6 Additionally, there is experimental evidence on the significant role of ROCK activation in the development of cardiac hypertrophy, remodeling, and ventricular dysfunction. In Dahl salt-sensitive hypertensive rats, increased left ventricular weight was significantly ameliorated by using the ROCK inhibitor Y-276327. 7 Upregulated RhoA protein, ROCK gene expression, and myosin lightchain phosphorylation in the hypertrophy stage were also suppressed by the ROCK inhibitor. 7 In hypertensive rats, the ROCK inhibitor fasudil attenuated myocardial fibrosis possibly through suppression of monocyte/macrophage infiltration of the heart. 8 Moreover, ROCK is significantly activated in the aortic wall in normotensive rats with genetically high angiotensin I-converting enzyme and angiotensin II, and it causes activation of genes that promote vascular remodeling, such as monocyte chemoattractant protein 1, transforming growth factor β1, and plasminogen activator inhibitor 1, and also increases vascular oxidative stress. 9 In Dahl salt-sensitive hypertensive

Research paper thumbnail of Veinte años de cirugía reparadora de la válvula mitral

Revista médica de Chile, 2014

JoSefina almeida Z. a , aldo meneSeS o. a , cecilia muñoZ c., Samuel cóRdova a. Twenty years of m... more JoSefina almeida Z. a , aldo meneSeS o. a , cecilia muñoZ c., Samuel cóRdova a. Twenty years of mitral valve repair. An experience in 322 patients Background: Mitral valve repair is the preferred procedure for the surgical treatment of mitral valve insufficiency (MI), procedure that we initiated 20 years ago. Aim: To assess our experience and long-term results of mitral valve repair. Patients and Methods: The database of the cardiology department was reviewed for the period between December 1991 and December 2012. A total of 322 patients aged 18 to 89 years (62% males) undergoing mitral valve repair were identified. Long-term survival information was obtained consulting death certificate records of the Chilean Identification Service. The latest echocardiogram available was analyzed. Results: MI was degenerative in 144 patients (45%) and ischemic in 104 (32%). A prosthetic ring was used in all ischemic and in 92% of non-ischemic MI. Operative mortality was 7.5%, 13% in ischemic and 4.4% in non-ischemic MI (p < 0.01). Overall long-term survival was 14.1 years; 9.3 and 16 years for ischemic and non-ischemic MI, respectively (p < 0.001). Survival at 5, 10, 15 and 20 years was 79, 63, 54 and 42%, respectively. For degenerative MI survival at 5 and 10 years was 90 and 76% and for ischemic MI, it was 64 and 44%, respectively (p < 0.001). On a multivariate analysis the main predictors of late mortality were age, associated valvular disease and ischemic etiology. Echocardiographic follow-up was available for 223 patients; MI was absent in 53% and was mild in 29%. Conclusions: In a 20 years follow-up, mitral valve repair for MI had excellent long-term survival and echocardiographic results. The most common etiologies of MI were degenerative and ischemic diseases. The latter had a worst prognosis. The main predictors of long term mortality were age, associated valvular disease and ischemic etiology.

Research paper thumbnail of Enfermedad cardíaca por carcinoide

Revista chilena de cardiología, 2011

Research paper thumbnail of Endocarditis infecciosa por Listeria monocytogenes: revisión de la literatura a partir de un caso clínico

Revista chilena de infectología, 2013

Research paper thumbnail of Strain y Strain rate auricular izquierdo evaluado por speckle tracking está relacionado a PCR ultrasensible en adolescentes obesos

Revista chilena de cardiología, 2011

Research paper thumbnail of 279 Usefulness of tissue doppler imaging in the detection of residual constriction post-pericardiectomy

European Journal of Echocardiography, 2006

Objectives: Vascular abnormalities are hallmarks of almost all systemic sclerosis patients. Impai... more Objectives: Vascular abnormalities are hallmarks of almost all systemic sclerosis patients. Impaired relaxation of the left ventricle is also characteristic for scleroderma heart disease. The aim of our study was to determine whether parameters of arterial stiffness correlate with echocardiographic indices of left ventricular relaxation impairment. Material: 21 patients with limited and diffuse scleroderma (18 women, mean age: 55±9 years) were studied. Methods: Parameters of local and systemic arterial stiffness (pulse wave velocity: PWV; augmentation index: Aix) were determined by automatic brachial pulse wave analysis (Arteriograph®). The same parameters and elastic modulus (Ep), stiffness index (ß), arterial compliance (AC) were measured on left brachial and common carotid arteries by echo-tracking (Aloka ProSound 5500). Indices of diastolic function were also determined with the same ultrasound system: in addition to the conventional Doppler parameters of the transmitral flow-early (E) and late (A) diastolic velocities, deceleration time (DT), isovolumic relaxation time (IVRT)-myocardial early (Ea) and late (Aa) diastolic velocities were measured at the lateral border of the mitral annulus using tissue Doppler imaging. E/A and E/Ea ratios were calculated. Simple associations between the variables were estimated by Pearson's method. Results: Carotid Ep showed significant correlations with both A (r=0.537, p<0.05) and E/A (r=-0.500, p<0.05) values, and correlated with IVRT also significantly (r=0.489, p<0.05). Carotid ß correlated with A (r=0.479, p<0.05), E/A (r=-0.548, p<0.05) and IVRT (r=0.564, p<0.01). Carotid AC correlated with A (r=-0.512, p<0.05), E/A (r=0.551, p<0.05) and IVRT values (r=-0.436, p<0.05). Carotid PWV and Aix showed similarly significant correlations with A, E/A, IVRT and with A and E/A values, respectively. Ep, ß and PWV determined by pulse-wave analysis and brachial artery echo-tracking did not correlate with the echocardiographic parameters of the left ventricular diastolic function. Brachial AC showed a significant correlation with A (r=-0.478, p<0.05) and DT (r=0.469, p<0.05). Significant correlation was found between Aix measured by pulse-wave analysis and Aa (r=0.560, p<0.05). Conclusion: Distensibility of elastic arteries correlates well with the echocardiographic indices of the left ventricular diastolic function, but stiffness of muscular type arteries is less useful to predict the degree of diastolic impairment. Selected parameters of arterial stiffness are good predictors of diastolic dysfunction in scleroderma patients ±.

Research paper thumbnail of Insuficiencia tricuspídea aislada

Revista chilena de cardiología, 2009

Research paper thumbnail of Asociación entre strain y strain rate auricular izquierdo evaluado por speckle tracking y fibrilación auricular post cirugía de revascularización miocárdica

Revista chilena de cardiología, 2011

Research paper thumbnail of Niveles de péptido natriurético cerebral y su relación con capacidad funcional y hemodinamia pulmonar en pacientes con hipertensión pulmonar primaria: Correlation with functional capacity and hemodynamic parameters

Revista médica de Chile, 2006

Research paper thumbnail of Falla cardio-respiratoria severa tratada con asistencia cardiopulmonar extracorpórea: Caso clínico

Revista médica de Chile, 2002

... Figura 3. Gráfico que muestra la evolución de la PaO 2 , proteína C reactiva (PCR), y flujo d... more ... Figura 3. Gráfico que muestra la evolución de la PaO 2 , proteína C reactiva (PCR), y flujo de la bomba centrífuga durante los cinco días de estadía en ventilador. Se aprecia la mejoría inmediata de la PaO 2 al entrar en asistencia ...

Research paper thumbnail of Diagnostic value of cerebrospinal fluid adenosine deaminase determination

Scandinavian Journal of Infectious Diseases, 1991

We measured the activity of adenosine deaminase (ADA) in the cerebrospinal fluid of 3 patients wi... more We measured the activity of adenosine deaminase (ADA) in the cerebrospinal fluid of 3 patients with tuberculous meningitis, 38 with viral meningitis, 15 with bacterial meningitis, 5 with malignant lymphoma, 11 with cerebrovascular diseases and 13 with miscellaneous neurological disorders. The highest ADA activities were observed in patients with tuberculous meningitis (median 21.3 U/l, range 20.0-23.0) and lymphoma (13.0 U/l, range 4.0-25.0). The sensitivity of the test for diagnosing tuberculous meningitis was 100% and the specificity 99% when a cut-off value of 20.0 U/l was used. We conclude that determination of ADA in cerebrospinal fluid is useful for the diagnosis of tuberculous meningitis, but that high activity also can be seen in some other CNS disorders, e.g. lymphoma with meningeal involvement.