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D Rivas

Publications and source records attributed to D Rivas.

9 recordsLinked to original sources
PubMed1996

Current role and future perspectives for radiofrequency catheter ablation of postmyocardial infarction ventricular tachycardia.

The most common substrate for ventricular tachycardia (VT) is a postmyocardial infarction (MI) scar. Radiofrequency catheter ablation (RFCA) in post-MI VT faces clinical, electrophysiologic, anatomic, and methodologic difficulties not found in many other human tachycardias. The pathophysiologic understanding of post-MI VT is incomplete; this influences the process of selecting RFCA target sites, which is time consuming, demands catheter stability, and has low sensitivity and predictive value for VT interruption by RF current. Improving and simplifying the methodology of RFCA in post-MI VT is badly needed. We review the pathophysiology of post-MI VT from the data reported on endocardial, epicardial, and intramural ventricular mapping obtained either intraoperatively or in a Langendorff perfused set-up in hearts from transplanted patients. From these studies we conclude that (1) some post-MI VT cases are not amenable to RFCA (reentry around the scar, VT having a subepicardial or deep intramural substrate, or a wide, extensive, subendocardial intrascar area of slow conduction); and (2) searching for the endocardial exit is advantageous for selecting the RFCA targets. We also comment on a new self-reference mapping catheter that allows the recording of high gain, noise-free, unfiltered and filtered unipolar signals as well as unipolar pacing. Among the unresolved issues in these patients is the meaning of fast nonclinical VT induced after successful RFCA of the clinical VT, which may explain why a substantial number of these patients still receive an implantable cardioverter-defibrillator.

Catheter Ablation↗
PubMed1996

[Antithrombotic therapy in atrial fibrillation].

The known risk of embolic events in patients with recurrent or chronic atrial fibrillation makes it mandatory to recommend oral anticoagulation in patients with rheumatic mitral valve disease, specially mitral stenosis to maintain an INR between 2.0 and 3.0. If despite this treatment recurrent embolism occurs, the dose of oral anticoagulants should be increased (INR between 2.5 and 3.5) or dipyridamole (200 to 400 mg/day) or aspirin (160 to 320 mg/day) should be added to dicoumarinic drugs. In patients that must be cardioverted either electrically or pharmacologically and who have been on atrial fibrillation for more than 2 days, oral anticoagulation should be maintained for 3-4 weeks before cardioversion and for 3-4 weeks after regaining sinus rhythm. Transesophageal echocardiography may enable us to identify the group of patients with low risk for an immediate cardioversion. In patients under 60 years of age with atrial fibrillation and no evidence of associated cardiovascular abnormality (lone atrial fibrillation) the embolic risk is very low and antithrombotic therapy is probably not needed. In subjects over 60 years of age with a low risk profile (absence of previous stroke, heart failure or systemic hypertension) aspirin (300-325 mg a day) seems to offer sufficient protection against embolic events. In patients at a higher embolic risk (history of previous cerebral ischemic attacks, heart failure of left ventricular dysfunction, systemic hypertension) oral anticoagulation unless contraindicated, should be recommended (INR 2.0-3.0). The role of other antithrombotic agents such as ticlopidine or triflusal to prevent embolic events in patients with atrial fibrillation is unknown.

Atrial Fibrillation↗
PubMed1995

Upregulated expression of IL-4 receptors and increased levels of IL-4 in rheumatoid arthritis patients.

The level of IL-4R expression on peripheral lymphocyte subsets from rheumatoid arthritis (RA) patients and controls was studied by flow cytometric analysis of the binding of phycoerythrin-labelled IL-4 (PE-IL-4). In normal lymphocytes, IL-4R is mainly expressed on CD19+ cells, although it was also seen, at lower levels, on CD3+, CD4+ and CD8+ cells. In RA patients, a significantly increased spontaneous expression of IL-4R was observed, compared with controls, in the CD3+, CD4+ and CD19+ cell subsets. No significant differences in IL-4R expression were found between patients receiving steroids and those who were not, suggesting that steroids are not involved in upregulating IL-4R levels in vivo. Because IL-4 is a potent upregulator of IL-4R, we considered the possibility that incremented levels of circulating IL-4 in RA accounted for the high surface expression of IL-4R. By ELISA, we found abnormally high levels of immunoreactive IL-4 in 35.13% of patient serum samples, while it was undetectable in control sera. In addition, we examined IL-4 mRNA expression by polymerase chain reaction (PCR) in the PBMC of patients and controls. IL-4 PCR products were observed in four out of 10 patients studied but in none of the controls. No correlation was observed between the seric concentrations of IL-4 and IL-4R, indicating that activator factors other than IL-4 contribute to the upregulation of IL-4R expression in RA. Since the patients' sedimentation rate and CRP values did not correlate with the concentration of circulating IL-4, we conclude that this lymphokine does not contribute to the deleterious effect of the disease. Rather, due to its antiinflammatory properties, the overproduction of IL-4 in RA may be a compensatory mechanism neutralizing the harmful effect of activated macrophages.

Aged↗
PubMed1995

Soluble, but not immobilized, anti-IgM antibody inhibits post-activation events leading to T-cell-dependent B-cell differentiation.

The potential for surface immunoglobulin-binding ligands to modify B-cell differentiation responses induced by activated T cells has been investigated. Activated T cells in human splenic mononuclear cells cultured on anti-CD3-coated plates induced B cells to produce large amounts of IgM and IgG. In this experimental system, cross-linking of B-cell antigen receptors by soluble, bivalent monoclonal or polyclonal anti-IgM antibodies completely inhibited IgM production, and greatly diminished IgG production, in a dose-dependent manner. Similar results were obtained using a F(ab')2 fragment of a goat anti-IgM antibody. Inhibition of B-cell differentiation by bivalent cross-linking reagents did not require the presence of antigen-presenting cells (APC), as comparable results were obtained in co-cultures of purified T and B cells. In contrast, enhanced immunoglobulin secretion was seen when surface IgM was cross-linked using anti-IgM antibody immobilized on the culture plate. Interestingly, activated T cells induced similar levels of expression on B cells of the activation antigens CD23, CD25 and CD71, and of class II molecules, irrespective of any treatment with soluble or immobilized anti-IgM antibody. This indicates that soluble anti-IgM specifically inhibits B-cell differentiation without altering initial events of T-cell-dependent B-cell activation.

Antibodies, Anti-Idiotypic↗
PubMed1994

Decrease in detectable complement receptor type 1 levels on erythrocytes from patients with psoriatic polyarthritis.

The complement receptor type 1 (CR1) levels on erythrocyte membranes from 23 patients with PsA was determined by using ELISA. Six patients had an axial form, the rest had peripheral arthritis (10 polyarthritis and seven oligoarthritis). A significant decrease in levels of this receptor was found in patients with polyarthritis compared with healthy controls. Non-significant differences were found when comparing the other two groups of patients with the controls, although the mean values of CR1 were lower in the patients' group. We also found an inverse correlation between CR1 levels and articular index, but not with ESR, CRP or disease duration. No differences in the CR1 density were obtained for HLA-B27 positive and HLA-B27 negative patients.

Adult↗
PubMed1993

Differential expression of IL-4 receptors in human T and B lymphocytes.

IL-4R have been described in unstimulated human T and B lymphocytes. However, a precise comparative study on the expression and regulation of IL-4R in isolated human T and B cell populations has not yet been fully assessed. We examined the mRNA levels and the cell membrane expression of IL-4R in freshly isolated T and B lymphocytes as well as in in vivo- and in vitro-stimulated cells. IL-4R protein expression and transcript levels were higher in tonsillar unstimulated B cells than in T cells. Splenic and peripheral blood B lymphocytes also expressed higher surface IL-4R in their membranes than T cells did. Large B lymphocytes from tonsils (in vivo-activated cells) obtained by Percoll gradient centrifugation displayed higher IL-4R levels than resting cells. On activation in vitro of T lymphocytes with IL-2 or PHA, slight increments on the IL-4R mRNA and protein levels were achieved. However, maximal levels of IL-4R expression were obtained on T cell incubation with IL-4 at a concentration of 100 U/ml. Similarly, the same concentration of this lymphokine up-regulated the surface IL-4R molecules and the IL-4R mRNA levels in purified B lymphocytes. Cross-linkage of surface Ig by insolubilized anti-IgM potentiated the effect of IL-4 in up-regulating IL-4R expression in B cells, probably by inducing outgrowth of IL-4R positive subpopulations. The B cell mitogen, Staphylococcus Aureus Cowan I, although inducing cell proliferation, was ineffective in promoting new receptor synthesis. Cell proliferation was not required for IL-4-dependent IL-4R up-regulation on both T and B lymphocytes.

Adult↗
PubMed1990

Upper urinary tract filling defects: flexible ureteroscopic diagnosis.

There were 62 patients referred to our institution for evaluation of upper urinary tract filling defects. These patients had undergone any of several diagnostic evaluations, including computerized tomography, B-mode ultrasound scanning and urinary cytology studies with or without upper tract brush biopsy. In all cases a conclusive diagnosis could not be formulated. With the use of flexible ureteropyeloscopy complete evaluations of the upper tract lesions were performed. The upper tract endoscopic procedure provided the diagnosis in all patients, as well as allowed for therapeutic intervention in 19. There was no significant morbidity associated with any procedure. We advocate the continued development of flexible ureteropyeloscopic instrumentation and procedures. We suggest the inclusion of ureteropyeloscopy with tissue sampling of neoplasms in the evaluation of all upper urinary tract lesions, except when diagnostic ultrasound correlates the characteristics and position of the lesion as calculous disease.

Endoscopes↗
PubMed1988

Effect of continued oral feeding on clinical and nutritional outcomes of acute diarrhea in children.

One hundred twenty-eight nonmalnourished male patients between 3 and 36 months of age were randomly assigned to receive one of four lactose-free dietary treatments to determine the effect of dietary therapy on the severity and nutritional outcome of diarrheal illness. Group 1 received a formula diet composed of casein, sucrose, dextrin with maltose (Dextri-Maltose), and vegetable oil to provide 110 kcal/kg body weight/d (CSO-110). Group 2 received CSO to provide 55 kcal/kg/d (CSO-55) for 2 days and then CSO-110. Group 3 received only oral glucose-electrolyte solution (GES) for 2 days, CSO-55 for the next 2 days, and then CSO-110. Group 4 received the same diets as Group 3 except that only intravenous GES was used for the first 2 days. The GES maintenance solutions provided 24 to 30 kcal/kg/d. Therapeutic success rates were similar among dietary groups, ranging from 90% to 97%. Fecal excretion was initially lower in group 4 (P less than 0.05) but was similar initially among groups treated orally and among all four groups beginning on day 3. Net apparent absorption of nitrogen, fat, carbohydrate, and total energy; retention of nitrogen; and increments in body weight, arm circumference, and skin-fold thickness were positively related to the amounts of dietary energy consumed. Thus continued oral feeding with the CSO diets during the early phase of therapy yielded improved nutritional results.

Absorption↗