Revista portuguesa de cardiologia : orgão oficial da Sociedade Portuguesa de Cardiologia = Portuguese journal of cardiology : an official journal of the Portuguese Society of Cardiology
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In order to be valid, clinical studies must be methodologically rigorous. The internal validity of a study is of crucial importance: a study is valid if its results are an unbiased estimation of the true result. In this case, the validity is internal because it refers to the group of patients under study and not necessarily different ones (external validity or applicability). ⋯ On the other hand, a study with too large a sample is harder to conduct and more costly. The goal of planning the sample size is to estimate the appropriate number of research subjects for the study. In this paper we will present and discuss the methodological principles underlying calculation of sample size: outcomes, type I and II error, alpha and beta, study power and variability.
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Review Case Reports
Levosimendan: a new approach for the treatment of patients with severe heart failure. A brief summary based on a clinical case.
Looking at the clinical report of a single patients admitted with severely decompensated heart failure and successfully managed with levosimendan, the authors review the current knowledge about this new drug. The treatment of severely decompensated heart failure is currently based on classical catecholamines (dopamine and dobutamine). ⋯ More recently a new concept has been introduced regarding a new way to improve myocardial contractility and vasodilation based on calcium-sensitizing properties with additional action on adenosine triphosphate-sensitive potassium channels. Levosimendan is a representative of this new class recently launched in the Portuguese market.
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Biography Historical Article
Chagas' disease and the involvement of the autonomic nervous system.
Chagas' disease is a major endemic disease in Latin America and a great cause for concern due to its high incidence: it afflicts 16 to 18 million individuals and places over 90 million people at risk of infection. At present, five mechanisms can be proposed to explain the pathogenesis of chronic Chagas cardiopathy: 1. direct lesion of the tissue by Trypanosoma cruzi; 2. dysfunction of the autonomic nervous system (neurogenic concept); 3. microvascular disease; 4. immunologic reaction; 5. alterations in the extracellular matrix. The neurogenic concept is the most attractive explanation for the pathogenesis of chronic Chagas cardiopathy through the involvement of the autonomic nervous system, an issue that has been prominent ever since Chagas first initiated research in the field. ⋯ Further evidence of autonomic nervous system dysfunction in Chagas' disease as a factor modulating complex ventricular arrhythmias was demonstrated by Pedrosa (RJ), who reported on a specific group of chronic Chagas patients with complex ventricular arrhythmias and dilated cardiopathy. In this study, when serum from chronic Chagas patients showing neither complex ventricular arrhythmias nor ventricular dilation was inoculated in isolated rabbit hearts, it produced no harmful effect in the conduction system, in contrast to what was observed in the conduction system of rabbits inoculated with serum from the Chagas patients group with complex ventricular arrhythmias and ventricular dilatation. These facts confirm Carlos Chagas as the pioneer in postulating involvement of the autonomic nervous system in Chagas' disease, and provide an important opportunity to understand ventricular involvement in chronic Chagas cardiopathy.
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The authors describe a case of a patient with inoperable bladder cancer, who was admitted with syncope and arterial hypotension. After examination, an echocardiogram was requested, which showed a free-floating thrombus in the right atrium and dilatation of the right chambers. ⋯ Despite a recent hemorrhagic event related to the bladder cancer, thrombolytic therapy was begun with improvement of the patient. The final echocardiogram was almost normal, without pulmonary hypertension and no dilatation of the right chambers.
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Complete situs inversus is a rare syndrome, with overall frequency estimated at 1/10,000 births, resulting from abnormal rotation of the cardiac tube during embryogenesis, of unknown mechanism. Recent studies suggest that left-right asymmetry defects are likely to be due to genetic abnormalities in the lefty, nodal, i.v., HAND, ZIC3, Shh, ACVR2B and/or Pitxz genes. In dextrocardia with situs inversus the heart is structurally normal in 90-95% of cases, in contrast to dextroversion (dextrocardia with situs solitus), which has a high incidence of structural cardiac defects. ⋯ They revealed complete situs inversus with corrected ostium secundum atrial septal defect. Finally, the anatomic, pathologic, embryologic and etiologic features of complete situs inversus and related abnormalities of the cardiac structures are presented. Special emphasis is given to genetic abnormalities, the study of which has seen great advances since the 1990s thanks to new techniques of DNA analysis.