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La eficacia de las estrategias para prevenir el tromboembolismo venoso en pacientes hospitalizados con riesgo para esta patología ha sido ampliamente demostrada. Con el reconocimiento de un número creciente de factores de riesgo para la recurrencia del tromboembolismo venoso, el análisis clínico se ha tornado complejo. Como la embolia de pulmón continúa siendo la causa evitable más común de muerte intrahospitalaria, es necesario mejorar la aplicación de las estrategias de prevención basadas en la evidencia, aunque todavía existe controversia en aspectos no resueltos. Debe estimularse la aplicación de programas locales de prevención. También las guías para el uso apropiado de las estrategias de prevención del tromboembolismo venoso deberían ser aplicadas y difundidas por todas las sociedades científicas médicas y quirúrgicas.

The efficacy of prophylactic strategies to prevent venous thromboembolism (VTE) in at risk hospitalised patients has been well demonstrated. With the recognition of an increasing number of risk factors for recurrence, the picture becomes increasingly complex. Because pulmonary embolism remains the most common preventable cause of in hospital death, evidence based thromboprophylaxis should be better. Many controversial exist regarding unresolved issues. Work is needed to improve prevention of VTE in hospitalised patients. Local programmes are effective and should be promoted. Guidelines supporting the appropriate use of prophylactic strategies should be endorsed by all medical and surgical societies.

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Tratamiento de la enfermedad cardiovascular trombótica. Replanteo del riesgo-beneficio
Thrombotic cardiovascular disease treatment. Risk/benefit ratio
RAÚL ALTMAN, OSCAR VIDAL

El sistema hemostático es un proceso fisiológico que previene la hemorragia y mantiene el balance entre la formación de un coágulo y la fluidez de la sangre. En la patología arterial, el coágulo se forma sobre la ruptura de un ateroma cuyo crecimiento dependerá de la subsecuente activación plaquetaria, de la concentración de trombina en la superficie del coágulo y de los cambios locales en la velocidad del flujo sanguíneo. Por lo tanto, el crecimiento de un coágulo puede ser inhibido bloqueando la trombina unida al trombo o inhibiendo la función plaquetaria. Los efectos de la terapéutica se consiguen directamente inhibiendo la actividad de la trombina o la función plaquetaria, pero la inhibición de una de ellas puede, simultáneamente, afectar a la otra actividad. Los tratamientos antitrombóticos combinados presentan mayor riesgo y se asocian con una mayor incidencia de hemorragias, especialmente en los pacientes de edad avanzada, aquellos con patologías hepáticas o renales, o quienes irán a revascularización temprana. La posibilidad de que las drogas antitrombóticas puedan aumentar la trombosis en lugar de prevenirla (efecto paradojal) también se discute en este artículo.

The hemostatic system is a physiological process to prevent hemorrhage and maintain a balance between clot formation and fluidity of blood in the circulation. After endothelial injury, platelets adhere to the exposed subendothelium and are activated by locally released agonists to stimulate thrombin formation, contributing to hemostatic control. In arterial disease, clots form upon atheroma rupture. After a clot starts to form, its growth depends on platelet activation, concentration of thrombin at the surface of the clot, and changes in local blood flow. Thus, clot growth can be inhibited by blocking thrombus-bound thrombin activity and/or by inhibiting platelet function. Thrombin is the strongest platelet agonist, and inhibition of thrombin can also prevent platelet activation. In fact, any intervention singly directed at thrombin activity or platelet activation may simultaneously affect the other function. Aspirin and clopidogrel are the mainstay antiplatelet therapies for arterial disease and combined with heparin, constitute the main treatments for acute coronary disease. Aspirin, despite its limitations, is considered the gold standard for arterial antithrombotic therapy. Acting through different platelet receptors, administration of aspirin plus clopidogrel enhances platelet inhibition. However, the beneficial effects of combined treatment over of aspirin alone in preventing thrombosis is still under debate. Actually, new antiplatelet or oral anticoagulant (antithrombin, anti-factor Xa) drugs, or therapies that include multiple antiplatelet drugs affecting primary hemostasis or a combination of antiplatelets and anticoagulants, are more aggressive therapy than aspirin, heparin or warfarin. Combined antithrombotic treatment confers particular risk and is associated with a higher incidence of bleeding, especially among older patients, patients with hepatic or renal diseases and patients undergoing early revascularization. The new monotherapies or the combining therapies (clopidogrel or prasugrel and aspirin) causes more bleeding than monotherapy with aspirin. Moreover, the possibility that antithrombotic drugs can cause increase of thrombosis instead it prevention (paradoxical effect) will be discussed.

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La ardua comprensión de la definición del infarto del miocardio
For the best understanding of what myocardial infarction means
ENRIQUE GURFINKEL

Durante los últimos treinta años, la definición de infarto de miocardio se convirtió en una forma dogmática de diagnóstico frío. El hecho consumado. Una definición inapelable. En estos últimos 30 años se desarrollaron conceptos más que trascendentes. Entre ellos el de sospecha de infarto, que modificó la manera de asociar el diagnóstico con la oportunidad de tratar y evitar decenas de muertes. La nueva definición de infarto combina la urgencia de su significado y la oportunidad médica. Esto significa diagnóstico en caliente y ejecución terapéutica. El mensaje más trascendente es el de buscar de cualquier manera el diagnóstico de infarto, recordando que no sólo la determinación química capaz de establecer al menos un gramo de necrosis miocárdica significa infarto. Esto no es definitivo. Es sólo el comienzo de una nueva manera de definir el futuro. La pericia médica está ante todo, y aquí en particular.

During the last 30 years, myocardial infarction definition was extremely tough, strong enough to give a chance of a doubt. Nowadays, we are able to call that as a could pursuit diagnosis. A late diagnosis for taking any therapeutic strategy in order to save a human life. Suspected diagnosis of myocardial infarction means the opportunity to convince much more individuals to reduce mortality.
This is a key point. A new definition includes the novel concept of "hot pursuit diagnosis" in order to keep in mind the chance to offer reperfusion to those with a chest pain irrespectively of ST segment alteration. However, the major message of this novel definition is to look for the diagnosis as soon as we can do it.
In the light of several tools we have today, a rapid presumption of myocardial infarction means much more that we can imaging. We do not need to wait for a simple blood determination of myocardial necrosis. The clinical skills or even imaging diagnosis may serve to support the idea of suspected up coming diagnosis of myocardial infarction.
Three decades are looking us. Technology and knowledge are changing and challenge our mind. This is not the end. This is just the beginning.

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El tromboembolismo venoso es una patología frecuente, con elevada morbimortalidad intrahospitalaria. En la actualidad se dispone de estrategias de prevención que permiten reducir su incidencia, complicaciones, morbimortalidad y costos. Sin embargo un importante número de pacientes hospitalizados no las reciben. En un hospital de la provincia de Santa Fe se evaluó la aplicación de medidas preventivas para el tromboembolismo venoso, y se realizó una intervención educativa posterior para optimizar la conducta del equipo médico, valorándose tres meses después el resultado de la intervención propuesta. La prevalencia de factores de riesgo y la alta tasa de omisión hallada concuerdan con los reportes de otros investigadores. ¿Por qué no podemos hacerlo mejor?

Venous thromboembolism (VTE) is a frequent disease with high morbi-mortality and is responsible for 10% of hospital deaths. Its incidence and associated morbi-mortality can be reduced with available strategies but only few in-hospital patients receive them.
Material and methods.
Prospective evaluation of preventive strategies application, followed by educative intervention to improve medical behaviour when necessary, and re-evaluation three months after changes were introduced.
Results. A total of 808 patients were evaluated, 406 at baseline and 402 after an intervention: 84% had risk factors for VTE and 33.7% had 3 or more risk factors. Only one in three of high risk patients received prophylaxis, and the educative intervention failed to improve medical behaviour.
Conclusions. The prevalence of VTE risk factors as well as the omission in preventive strategies application were similar to the ones reported by other investigators. Our intervention, based on lectures tailored to each hospital service and posters left at each nurse station, failed to overcome the omissions.

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Oxido nítrico y remodelamiento de arterias mamarias de bypass coronario. Impacto de la hipertensión arterial
Nitric oxide and remodelling patterns in mammary arteries used in coronary by-pass. Impact of arterial hypertension
CLAUDIO JOO TURONI, RODRIGO MARAÑÓN, JUAN MUNTANER, VÍCTOR PROTO, MARÍA PERAL DE BRUNO

La hipertensión arterial produce cambios funcionales y estructurales de los vasos en los que estaría implicado el óxido nítrico. En nuestro laboratorio se constató que las arterias mamarias de bypass coronario, aun en presencia de disfunción endotelial, producían liberación de óxido nítrico por activación de una óxido nítrico sintetasa neuronal extraendotelial. La hipertensión arterial indujo un remodelamiento vascular concéntrico en arterias mamarias; sin embargo, el espesor de la pared se mantuvo a expensas de una disminución de las células musculares lisas vasculares. Los hallazgos de este trabajo apoyan la hipótesis de que el óxido nítrico extraendotelial estaría implicado también en los cambios estructurales a través de la activación de óxido nítrico sintetasas de las células musculares lisas vasculares.

Arterial hypertension (HTA) produces functional and structural changes of the vessels in those that it would be implied the nitric oxide (NO). In coronary by-pass surgery mammary arteries (AM) are used. These vessels would lend bigger viability than the saphenous veins. In our laboratory we find that AM, even endothelial dysfunction, showed NO release for activation of a extraendothelial neuronal NO-syntase.
Objectives. To determine, in AM of patients with and without HTA, the presence and type of remodelling and the relation between HTA and NO-release.
Material and method. Patients from programmed by-pass surgery have been divided according to clinical history in two groups: GH (with HTA) and GN (without HTA). AM rings of surgical remains were placed in vitro to 2 g preload. Nitrites contents were measured by colorimetric method (Griess Reaction) and endothelium presence was studied by relaxation to acetylcholine in noradrenaline-precontracted AM and by histology evaluation (presence anti-CD34). To study remodelling pattern, sections of AM were stained with H&E and PAS and to the off-line analysis of the sections, the software Image J was used.
Results. We find absence of endothelium (E-) in 92.3% of the patients. In AM E- of GH values of NO were smaller than in GN (1024 ± 76 n = 18 vs 1476 ± 121, n = 14 pmol/mg tissue; p < 0.003). AM E- of GH showed smaller lumen/wall relation than AM of GN (0.21 ± 0.03; n = 6 vs 0.75 ± 0.17; n=10; p < 0.05) with a decrease of the arterial lumen but without alteration of wall thickness. Number of nuclei in GN was 97.5 ± 11.0 vs 48.5 ± 2 in GH (n = 12, en 1C/40X p < 0.001). This finding was correlated with NO levels (r = 0.34, p < 0.04).
Conclusions. HTA induced a concentric remodelling pattern, in AM. However, wall thickness stayed constant to expense of diminution of number of CMLV. The NO release in AM E- is in agreement with previous observations, supporting in this work the hypothesis that the extraendothelial NO would be also implied in the structural changes through the activation of NOS present in the CMLV.

Tratamiento con alteplasa en infarto cerebral en la Unidad de Stroke (Registro TAICUS)
Thrombolysis with rt-PA for acute ischemic stroke
PABLO CLEMENTTI, BENJAMÍN WAJSER, CARLOS SZULMAN, LUIS OLLETA, LAURA VIDAL, MARIELA VELÁSQUEZ, STELLA CASTAÑEDA, MARCELO MALLAGRAY, JUAN MUNTANER, ANDREA PIREDDA

El uso del activador tisular del plasminógeno está considerado uno de los más importantes avances terapéuticos desde que la Food and Drug Administration aprobó, en 1996, su empleo para el ataque cerebrovascular isquémico agudo que reúna los criterios de la National Institute of Health Stroke Scale. En un registro realizado en nuestra institución (Registro TAICUS) se incluyó a los pacientes que ingresaron dentro de las tres horas desde el comienzo de los síntomas con el fin de evaluar su evolución después de la administración endovenosa de activador tisular del plasminógeno, y la seguridad de su empleo en una unidad de stroke. El Registro mostró que la trombólisis endovenosa con activador tisular del plasminógeno puede mejorar la evolución temprana del accidente cerebrovascular isquémico agudo y que su empleo sería seguro en las unidades de stroke.

Tissue plasminogen activator (rt-PA) in acute ischemic stroke, since FDA approved it in 1996, is one of the most important advances in stroke medicine. As we believe that there are too few data for rt-PA to be given to all patients with stroke who meet the NIHSS (National Institute of Health Stroke Scale) criteria, in our institution we performed a registry for ischemic stroke, trying to identify those within three hours of the onset of stroke to evaluate the safety and outcome of intravenous rt-PA, and also to evaluate how a safe implementation of thrombolysis for stroke can be improved in stroke care units.
Material and method. Fifty two consecutive cases of ischemic stroke patients with measurable neurological deficit were enrolled in the registry, from July 2006 to December 2007. Those included with onset of symptoms < 3 hours were eligibly for intravenous thrombolysis. At admission and discharge, NIHSS and modified Rankin Scale were performed. The rt-PA clinical activity was indicated by 4 points improvement over baseline values in the NIHSS score.
Results. A total of 17 patients (32%) with onset of symptoms < 3 hours were eligibly for thrombolysis. Nine of the 14 patients (27%) treated with rt-PA showed improvement in stroke symptoms, measured by two assessment scales (NIHSS and modified Rankin). Mortality rates was greater in untreated versus treated cases (31% vs. 14%).
Conclusions. TAICUS Registry shows that intravenous thrombolysis with rt-PA might improve early stroke outcomes and its management seems safe in stroke care units.

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La presencia de "muesca" en las extrasístoles ventriculares. ¿Un nuevo marcador de riesgo de muerte arrítmica? 
The presence of "notch" in the ventricular extrasystoles. A new marker of risk of arrhythmic death?
JORGE GARGUICHEVICH, ALFREDO D. MELCHOR, LAURA S. SANZIANI

Se describen por primera vez las características de un signo electrocardiográfico estrechamente relacionado con la génesis de arritmias ventriculares malignas. Consiste en una "muesca" que se visualiza al final del QRS o al comienzo del segmento ST de algunas extrasístoles ventriculares. Se describen siete casos de asociación de esta "muesca" con taquicardia ventricular. Se hace hincapié en el diagnóstico diferencial con la onda P y se resaltan sus características de intermitencia, de manifestación en algunas derivaciones solamente, y su ocurrencia espontánea o inducida por un evento isquémico, prueba de esfuerzo o extraestímulos ventriculares. Se relaciona su génesis con postdespolarizaciones precoces u onda J y se interpreta que es compatible con la presencia de un sustrato eléctrico capaz de conducir a la muerte arrítmica, aunque se recuerda que también se presenta en pacientes sin arritmias ventriculares malignas. Esto constituye una observación inicial y tanto el origen como el significado pronóstico de este hallazgo deberán ser analizados con mayor precisión en el futuro.

The objective of this study is to describe for the first time the characteristics of an electrocardiographic sign, that we have observed closely related to the genesis of malignant ventricular arrhythmias. It consists in a "notch" that is visualized at the end of the QRS or beginning of ventricular ST segment of some ventricular extrasystoles. In this study, seven cases of association of this "notch" with ventricular tachycardia are described. These have been selected from registries of patients of our institution or publications, after reviewing numerous Holter recordings or electrocardiograms in which the "notch" is present. It stands out that it is not an infrequent fact and that it also appears in patients without demonstrated malignant ventricular arrhythmias. The differential diagnosis with the P wave and its characteristics of intermission, the manifestation only in some leads of the ECG and its spontaneous occurrence or induced by an ischemic event, stress test or ventricular extrastimuli are emphasized. Its genesis is related with early afterdepolarizations or J wave, but to the margin of the arrhythmic mechanism, it is interpreted that the same one is compatible with the presence of an electrical substrate able to lead to the arrhythmic death. This only constitutes an initial observation and so its origin as well as its prognostic significance will have to be more accurately analyzed in the future.

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Las nuevas tecnologías incorporadas a los marcapasos son una herramienta de máxima utilidad durante el seguimiento. Se presenta un caso clínico en el que se reporta el funcionamiento inadecuado del sistema, puesto en evidencia mediante la evaluación de los electrogramas almacenados.

New pacemaker technologies are a most useful tool for clinical follow-ups to show events that are not evident in surface ECG's. In this case, inappropriate operation of the system due to stored EGM with no apparent clear explanation is reported.

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Patrón electrocardiográfico tipo Brugada luego de la administración oral de propafenona para el tratamiento de paroxismos de fibrilación auricular
Electrocardiographic changes consistent with Brugada syndrome induced with propafenone in patients treated for paroxysmal atrial fibrillation
MARCELO LANZOTTI, SILVANO DIANGELO, JORGE A. SALERNO-URIARTE, RAFFAELLA MARAZZI, ROBERTO DE PONTI, NORBERTO CITTA, ROBERTO LANZOTTI, HORACIO LOCATELLI, DANIEL PISKORZ, MARCELO MARIÑO, ALEJANDRO MEIRIÑO, MARIELA MACAGNO

El síndrome de Brugada se caracteriza por la presencia de un patrón electrocardiográfico de elevación del segmento ST en las derivaciones precordiales derechas, ausencia de cardiopatía estructural demostrable y episodios de síncope o muerte súbita debidos a taquiarritmias ventriculares. Se asocia con un alto riesgo de muerte súbita en jóvenes y adultos. Se presentan dos casos clínicos de individuos sin antecedentes de eventos sincopales ni historia familiar de muerte súbita cardíaca en quienes se observó un patrón tipo Brugada luego de la administración de propafenona oral para el tratamiento de los paroxismos de fibrilación auricular.

The Brugada Syndrome was introduced as a clinical entity in 1992, and is characterized by a distinct ST-segment elevation in the right precordial ECG leads. The syndrome is associated with a high risk for sudden cardiac death in young and healthy adults with structurally normal hearts. The ECG manifestations may be dynamic or concealed and could be unmasked by sodium channel blockers (propafenone) and other drugs and conditions. The present article reports two asymptomatic patients displaying a type 1 Brugada ECG after sodium channel blockade (propafenone) for paroxysmal atrial fibrillation. Considering the Report of The Second Consensus Conference of Brugada Syndrome, asymptomatic patients who have no family history and who develop a type 1 ECG only after sodium channel blockade, should be closely followed up.

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Seudoaneurisma como complicación tardía de cirugía de Blalock-Taussig
False aneurysm following modified Blalock-Taussig shunt
ALBERTO ROBREDO

La cirugía de Blalock-Taussig modificada con tubo de politetrafluoroetileno expandido se realiza como procedimiento paliativo para diversas cardiopatías congénitas cianóticas. La formación de un seudoaneurisma es una complicación tardía poco frecuente, pero bien conocida. Se presenta un paciente de 16 meses de vida que ingresó en colapso cardiovascular severo, secundario a un seudoaneurisma relacionado con la cirugía de Blalock-Taussig realizada en etapa neonatal. La sospecha clínica, la radiografía de tórax y el ecocardiograma Doppler permitieron el diagnóstico exacto. La angiografía selectiva mostró la anatomía vascular en detalle. Se realizó cirugía de urgencia por toracotomía izquierda, con evolución favorable al año.

The modified Blalock-Taussig shunt with an expanded polytetrafluorethylene graft is commonly performed as early palliation in cyanotic congenital heart disease. The pseudoaneurysm formation is a rare, but well-known, late complication of the modified Blalock-Taussig shunt. We report a 16-months-old patient with acute cardiovascular collapse secondary to perigraft pseudoaneurysm, 15 months after a modified Blalock-Taussig shunt. The clinical suspicion, chest x-ray film and echocardiography with Doppler-flow allowed the exact and early diagnosis. Cardiac catheterization with cineangiography revealed the anatomy in detail. An emergency operative procedure was recommended through a left thoracotomy, and no recurrence was noted on last follow-up 1.5 years postoperatively.

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Detección y caracterización de una placa vulnerable con tomografía multicorte
de 64 detectores. Análisis submilimétrico
Vulnerable plaque detected with multislice detector computed tomography
CARLOS RUBIO, CLAUDIO SUELDO PEREYRA, CARLOS R. RUBIO

Los síndromes coronarios agudos, en la mayoría de los casos, son consecuencia de la complicación de una placa vulnerable preexistente. Por lo tanto es de capital importancia reconocer sus características morfológicas, histológicas, biológicas y fisiopatológicas. Estos avances son la base para desarrollar métodos no invasivos para la detección temprana de estas placas. Se presenta el caso clínico de un paciente que consultó espontáneamente y a quien se le detectó, por tomagrafía multicorte de 64 detectores, una placa con características de vulnerabilidad y que, pocos días después de iniciar tratamiento preventivo con aspirina y estatinas, presentó un cuadro clínico compatible con un infarto agudo de miocardio.

Most of the acute coronary syndromes are due to a vulnerable plaque. It is essential to know the biologic, physiopatologic and anatomic characteristics of this kind of plaques and with this knowledge, develop invasive and non invasive methods for vulnerable plaque detection. We report one clinical case with a multislice detector computed tomography performed, detecting a vulnerable plaque. A few days later, just beginning treatment with aspirin and statines, presents at emergency department with an acute myocardial infarction. We describe the methodology used for plaque analysis and the future role of this modern technology.

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Publicación: Abril 2008