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Biomedical subjects

G Peña

Publications and source records attributed to G Peña.

At least 19 recordsLinked to original sources
PubMed2001

[Radiofrequency ablation of recurrent monomorphic ventricular tachycardia in a patient with severe systemic scleroderma].

A case of progressive systemic scleroderma in a 33 year-old woman who was referred to our Arrhythmia Unit due to daily palpitations and dizziness is presented. The 24-hour Holter recording showed monomorphic ventricular tachycardia which lasted several minutes. Hemodynamic study showed dilated right chambers and right ventricular dysfunction, without pulmonary hypertension. Left ventricular angiography and coronary arteries were normal. During programmed electrical stimulation, two different ventricular tachycardia were induced and ablated with radiofrequency on the right ventricle. The patient remains free of recurrence of tachycardia after (10 months of follow up). Patients with progressive systemic scleroderma may present several different cardiac arrhythmias. Involvement of the right ventricle is particularly frequent as is the origin of ventricular tachycardia in this ventricle. Radiofrequency catheter ablation is safe and effective in the management of these patients.

Adult↗
PubMed2001

[Macroscopic and microscopic study of the right coronary artery after radiofrequency catheter ablation of cavotricuspid isthmus in an experimental model].

INTRODUCTION AND OBJECTIVES: The right coronary artery (RCA) is found in the AV groove, just below the ablation target of atrial flutter, the cavotricuspid isthmus (ICT). After radiofrequency (RF) ablation with standard catheters, there have been no reports of complications, but it may not be successful in 10% of the cases. However, the use of irrigated tip catheters, which create deeper lesions, might potentially damage the coronary tree. METHODS: We analyzed the effects of ICT RF ablation on the coronary tree, with macroscopic and microscopic anatomopathological study. Ablation on ICT was performed using an irrigated tip catheter in 16 pigs and was randomly compared with a standard ablation catheter. There were no clinical problems, modifications of ST or new arrhythmias during the ablation. The heart was extracted at 1 week. RESULTS: The macroscopic study demonstrated that the right coronary artery was preserved, along the ICT, surrounded by the epicardial fat. The microscopic study showed an inflammatory reaction in the epicardial fat that reached the adventitia of the coronary artery, but never produced necrosis in 14 cases. The muscular wall of the artery had signs of focal inflammation without endothelium involvement in 2 cases. However, we found a subepicardial vein completely damaged by the radiofrequency. CONCLUSIONS: Although the right coronary artery is located just below the isthmus, no necrosis was observed in any case. However, there was an inflammatory reaction that focally reached the muscular wall. The veins may be damaged in RF ablation, perhaps due to the different blood flow of each vessel.

Animals↗
PubMed2001

[Evaluation of the anatomopathological characteristics and the safety of radiofrequency lesions at the atrial level with two different systems of irrigated tip catheters on an experimental level].

INTRODUCTION AND OBJECTIVES: We performed this study to evaluate the security and efficacy in the lesions produced on the atrial wall by different irrigated catheters in an experimental model. We evaluated the anatomopathologic characteristics of the lesions produced by two different systems of irrigated tip catheters, with opened or closed circuit. METHODS: This study was performed in 16 pigs applying 60 sec radiofrequency pulses with three different energy levels (15, 25 y 50 Watts). Two different systems of radiofrequency ablation irrigated catheters were used, opened and closed. We used 4 pigs in which we performed ablation with a standard catheter as a control group. Under fluoroscopic guidance, catheters were placed on the high and low right atrial lateral wall, where lesions were produced. After 7 days, animals were sacrificed for anatomopathological study. RESULTS: A total of 27 lesions were performed with irrigated catheters (11 closed circuit and 16 opened) and 6 with standard catheters in the control group. We did not find significant differences in the lesion characteristics between the two different systems of irrigated tip catheter used, nevertheless lesions performed with the closed system were slightly greater. Th lesions produced with irrigated catheters were always superior in the control group. Transmurality in the free atrial wall is frequent with both systems. We did not see any perforation in the atrial wall. CONCLUSIONS: We did not find significant differences in the size of the lesions produced with the two systems of irrigated catheters used. These data from an experimental model can provide useful information for atrial tachycardia radiofrequency ablation procedures in humans.

Animals↗
PubMed2001

Lack of efficacy of atenolol for the prevention of neurally mediated syncope in a highly symptomatic population: a prospective, double-blind, randomized and placebo-controlled study.

OBJECTIVES: This study was designed to evaluate the efficacy of atenolol for the long-term management of patients with vasovagal syncope. The primary hypothesis was that atenolol is not superior to placebo for the treatment of vasovagal syncope. BACKGROUND: There is no definitive well-controlled analysis of the efficacy of beta-adrenergic blocking agents in patients with recurrent vasovagal syncope. METHODS: This is a prospective, randomized, double-blind, placebo-controlled study. Fifty patients with recurrent vasovagal syncope were included (at least two episodes in the last year). A baseline tilt test was performed. Twenty patients (40%) had a positive tilt test. Intravenous atenolol prevented a second positive tilt in five patients. The patients were randomized to receive either atenolol or a placebo (26 patients atenolol 50 mg/day, 24 patients placebo). The follow-up procedure lasted one year. The primary end point of the study was the time to first recurrence of syncope. RESULTS: In the intention-to-treat analysis, the group treated with atenolol had a similar number of patients with recurrent syncopal episodes as the placebo group. The Kaplan-Meier actuarial estimates of time to first syncopal recurrence showed that the probability of remaining free of syncope drops similarly in both groups and that there was no statistical difference between both curves (patients treated with atenolol vs. the placebo) with a log-rank test p value of 0.4517. CONCLUSIONS: The recurrence of neurocardiogenic syncope in highly symptomatic patients treated with atenolol is similar to that of patients treated with placebo.

Adolescent↗
PubMed2000

[Anatomopathological and biochemical correlation of lesions produced by standard and irrigated 4 mm radiofrequency catheters].

INTRODUCTION AND OBJECTIVES: The influence on the size of radiofrequency lesions by cooling of the tip of the electrode remains unclear. Moreover, the possible effects of two different cooling systems, closed and open, have not been well differentiated. We designed this study to compare both systems of irrigated-tip catheters and the lesions produced with standard 4 mm catheters and also to evaluate the pathological and biochemical marker release correlation (cardiac troponin I) in an experimental model. METHODS: The study was performed in 20 pigs. Applying between 1-8 radiofrequency pulses, at a power of 15, 25 or 50 watts, for 15-60 seconds to each animal. After 7 days, the pigs were sacrificed for anatomopathological study. RESULTS: A total of 54 lesions were produced, 25 with standard catheters and 29 with irrigated catheters. The mean volume of the lesions produced with standard catheters was 146 +/- 110 microl and with irrigated-tip catheters 856 +/- 864 microl (p < 0.001). Peak values of cardiac troponin I were also higher for irrigated catheters (18 +/- 15 ng/ml) than for standard (6.5 +/- 3 ng/ml). The correlation between the size of the lesion and the levels of cardiac troponin I were 0.86 and 0.79 with the standard and irrigated-tip catheters, respectively. The incidence of cratering was higher with standard catheters (60%) than with irrigated (27%). CONCLUSIONS: The lesions produced with an irrigated catheter are greater than those observed with standard catheters. The mean peak value of postablation cardiac troponin demonstrate a good correlation with the real size of the necrosis.

Animals↗
PubMed1999

Evaluation of a fluorescence-polarization assay for the diagnosis of bovine brucellosis in México.

A homogeneous fluorescence-polarization assay (FPA) was used for the serological diagnosis of bovine brucellosis in México. The assay uses O-polysaccharide prepared from Brucella abortus lipoplysaccharide (20-30 kDa) conjugated with fluorescein isothiocyanate as a tracer. To measure the fluorescence polarization, a FPM-1 fluorescence-polarization analyzer was used with the procedure described by Nielsen et al. (1996b). A cut-off value of 90 millipolarization (mP) units was used for testing 560 bovine sera from different areas of México. (305 positive sera and 255 negative sera according to the complement fixation test; CFT.) Some were tested with the Rose Bengal plate (RB) test (n = 490) and some with the rivanol-agglutination (RIV) test (n = 190). Sensitivities were 98.3%, 99.3% and 99.0%, and specificities were 68.8%, 55.4% and 96.9%, respectively, for RB, RIV and FPA. The FPA gave a kappa coefficient of agreement with respect to CFT of 0.96, while RB and RIV (relative to the CFT) gave coefficients of 0.70 and 0.61, respectively. Finally, ROC analysis suggested a cut-off value which agreed with the one recommended in the test procedure. We concluded that FPA is a suitable test to be used instead of the CFT in Mexican conditions.

Animals↗
PubMed1998

Characterization of cry genes in a Mexican Bacillus thuringiensis strain collection.

Mexico is located in a transition zone between the Nearctic and Neotropical biogeographical regions and contains a rich and unique biodiversity. A total of 496 Bacillus thuringiensis strains were isolated from 503 soil samples collected from the five macroregions of the country. The characterization of the strain collection provided useful information on the ecological patterns of distribution of B. thuringiensis and opportunities for the selection of strains to develop novel bioinsecticidal products. The analysis of the strains was based on multiplex PCR with novel general and specific primers that could detect the cry1, cry3, cry5, cry7, cry8, cry9, cry11, cry12, cry13, cry14, cry21, and cyt genes. The proteins belonging to the Cry1 and Cry9 groups are toxic for lepidopteran insects. The Cry3, Cry7, and Cry8 proteins are active against coleopteran insects. The Cry5, Cry12, Cry13, and Cry14 proteins are nematocidal. The Cry11, Cry21, and Cyt proteins are toxic for dipteran insects. Six pairs of general primers are used in this method. Strains for which unique PCR product profiles were obtained with the general primers were further characterized by additional PCRs with specific primers. Strains containing cry1 genes were the most abundant in our collection (49.5%). Thirty-three different cry1-type profiles were identified. B. thuringiensis strains harboring cry3 genes represented 21.5% of the strains, and 7.9% of the strains contained cry11 and cyt genes. cry7, cry8, and cry9 genes were found in 0.6, 2.4, and 2.6% of the strains, respectively. No strains carrying cry5, cry12, cry13, cry14, or cry21 genes were found. Finally, 14% of the strains did not give any PCR product and did not react with any polyclonal antisera. Our results indicate the presence of strains that may harbor potentially novel Cry proteins as well as strains with combinations of less frequently observed cry genes.

Animals↗
PubMed1993

Effectiveness of iron-fortified infant cereal in prevention of iron deficiency anemia.

BACKGROUND: Iron deficiency continues to be a common problem among infants throughout the world. Iron-fortified formula is effective in preventing iron deficiency but the benefit of iron-fortified cereal is controversial. METHODS: We compared iron-fortified rice cereal to unfortified rice cereal in infants who were exclusively breast-fed for more than 4 months and to iron-fortified formula in infants who were weaned to formula before 4 months of age. The design was double blind in respect to the presence or absence of fortification iron in the cereal or formula and included 515 infants who were followed on the protocol from 4 to 15 months of age. Rice cereal was fortified with 55 mg of electrolytic iron per 100 g of dry cereal and infant formula with 12 mg of ferrous sulfate per 100 g of dry powder, levels approximating those in use in the United States. Measures of iron status were obtained at 8, 12, and 15 months. Infants with hemoglobin levels of < 105 g/L were excluded from the study and treated. RESULTS: Consumption of cereal reached plateaus at means of about 30 g/d after 6 months of age in the formula-fed groups and 26 g/d after 8 months in the breast-fed groups; these amounts are higher than the 19-g/d mean intake by the 73% of infants who consume such cereal in the United States. Among infants weaned to formula before 4 months, the cumulative percentages of infants excluded for anemia by 15 months were 8%, 24%, and 4%, respectively, in the fortified cereal, unfortified cereal and formula, and fortified formula groups (P < .01 unfortified vs either fortified group; the difference between the two fortified groups was not significant). In infants breast-fed for more than 4 months, the corresponding values were 13% and 27%, respectively, in the fortified and unfortified cereal groups (P < .05). Mean hemoglobin level and other iron status measures were in accord with these findings. CONCLUSION: Iron-fortified infant rice cereal can contribute substantially to preventing iron deficiency anemia.

Anemia, Hypochromic↗
PubMed1991

[Contribution of iron of bread to the Chilean diet].

The content and bioavailability of iron contained in Chilean bread was studied in a random sample from 301 bakeries. A wet digestion procedure followed by a colorimetric method was used. Iron bioavailability was examined in 9 adult women using the extrinsic radioactive tag method. The iron content of bread was 2.4 +/- 0.7 mg/100 g (normally distributed) and 71% of bakeries used wheat flour with adequate iron content. The geometric mean of iron absorption was high (10.5%). Simultaneous ingestion of milk or tea decreased iron absorption by 26 and 35%, respectively. These data suggest that bread represents an important source of iron in the diet of the Chilean population. Iron fortification of bread should be supported and improved nationwide.

Adult↗
PubMedDate not supplied

[A case of massive ascariasis in the riverside sector of the Riñihue lake, Chile].

A case of massive ascariasis in a three and a half years old girl who eliminated 104 worms after treatment with mebendazole is reported from a riverside sector of Riñihue Lake, Chile. Chilean literature about intestinal massive ascariasis is reviewed. Worms showed 12-29 cm of length and 0.2-5.5 g of weight. Total worms weighted 155.8 g.

Adult↗